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  • Sex and the Single Cell. II. There Is a Time and Place for Sex PLOS BIOLOGY Robinett, C. C., Vaughan, A. G., Knapp, J., Baker, B. S. 2010; 8 (5)

    Abstract

    The Drosophila melanogaster sex hierarchy controls sexual differentiation of somatic cells via the activities of the terminal genes in the hierarchy, doublesex (dsx) and fruitless (fru). We have targeted an insertion of GAL4 into the dsx gene, allowing us to visualize dsx-expressing cells in both sexes. Developmentally and as adults, we find that both XX and XY individuals are fine mosaics of cells and tissues that express dsx and/or fruitless (fru(M)), and hence have the potential to sexually differentiate, and those that don't. Evolutionary considerations suggest such a mosaic expression of sexuality is likely to be a property of other animal species having two sexes. These results have also led to a major revision of our view of how sex-specific functions are regulated by the sex hierarchy in flies. Rather than there being a single regulatory event that governs the activities of all downstream sex determination regulatory genes-turning on Sex lethal (Sxl) RNA splicing activity in females while leaving it turned off in males-there are, in addition, elaborate temporal and spatial transcriptional controls on the expression of the terminal regulatory genes, dsx and fru. Thus tissue-specific aspects of sexual development are jointly specified by post-transcriptional control by Sxl and by the transcriptional controls of dsx and fru expression.

    View details for DOI 10.1371/journal.pbio.1000365

    View details for Web of Science ID 000278759600003

    View details for PubMedID 20454565

  • Midline crossing by gustatory receptor neuron axons is regulated by fruitless, doublesex and the Roundabout receptors DEVELOPMENT Mellert, D. J., Knapp, J., Manoli, D. S., Meissner, G. W., Baker, B. S. 2010; 137 (2): 323-332

    Abstract

    Although nervous system sexual dimorphisms are known in many species, relatively little is understood about the molecular mechanisms generating these dimorphisms. Recent findings in Drosophila provide the tools for dissecting how neurogenesis and neuronal differentiation are modulated by the Drosophila sex-determination regulatory genes to produce nervous system sexual dimorphisms. Here we report studies aimed at illuminating the basis of the sexual dimorphic axonal projection patterns of foreleg gustatory receptor neurons (GRNs): only in males do GRN axons project across the midline of the ventral nerve cord. We show that the sex determination genes fruitless (fru) and doublesex (dsx) both contribute to establishing this sexual dimorphism. Male-specific Fru (Fru(M)) acts in foreleg GRNs to promote midline crossing by their axons, whereas midline crossing is repressed in females by female-specific Dsx (Dsx(F)). In addition, midline crossing by these neurons might be promoted in males by male-specific Dsx (Dsx(M)). Finally, we (1) demonstrate that the roundabout (robo) paralogs also regulate midline crossing by these neurons, and (2) provide evidence that Fru(M) exerts its effect on midline crossing by directly or indirectly regulating Robo signaling.

    View details for DOI 10.1242/dev.045047

    View details for Web of Science ID 000273091500014

    View details for PubMedID 20040498

  • Manipulation of an Innate Escape Response in Drosophila: Photoexcitation of acj6 Neurons Induces the Escape Response PLOS ONE Zimmermann, G., Wang, L., Vaughan, A. G., Manoli, D. S., Zhang, F., Deisseroth, K., Baker, B. S., Scott, M. P. 2009; 4 (4)

    Abstract

    The genetic analysis of behavior in Drosophila melanogaster has linked genes controlling neuronal connectivity and physiology to specific neuronal circuits underlying a variety of innate behaviors. We investigated the circuitry underlying the adult startle response, using photoexcitation of neurons that produce the abnormal chemosensory jump 6 (acj6) transcription factor. This transcription factor has previously been shown to play a role in neuronal pathfinding and neurotransmitter modality, but the role of acj6 neurons in the adult startle response was largely unknown.We show that the activity of these neurons is necessary for a wild-type startle response and that excitation is sufficient to generate a synthetic escape response. Further, we show that this synthetic response is still sensitive to the dose of acj6 suggesting that that acj6 mutation alters neuronal activity as well as connectivity and neurotransmitter production. RESULTS/SIGNIFICANCE: These results extend the understanding of the role of acj6 and of the adult startle response in general. They also demonstrate the usefulness of activity-dependent characterization of neuronal circuits underlying innate behaviors in Drosophila, and the utility of integrating genetic analysis into modern circuit analysis techniques.

    View details for DOI 10.1371/journal.pone.0005100

    View details for Web of Science ID 000265500700013

    View details for PubMedID 19340304

  • Blueprints for behavior: genetic specification of neural circuitry for innate behaviors TRENDS IN NEUROSCIENCES Manoli, D. S., Meissner, G. W., Baker, B. S. 2006; 29 (8): 444-451

    Abstract

    Innate behaviors offer a unique opportunity to use genetic analysis to dissect and characterize the neural substrates of complex behavioral programs. Courtship in Drosophila involves a complex series of stereotyped behaviors that include numerous exchanges of multimodal sensory information over time. As we will discuss in this review, recent work has demonstrated that male-specific expression of Fruitless transcription factors (Fru(M) proteins) is necessary and sufficient to confer the potential for male courtship behaviors. Fru(M) factors program neurons of the male central and peripheral nervous systems whose function is dedicated to sexual behaviors. This circuitry seems to integrate sensory information to define behavioral states and regulate conserved neural elements for sex-specific behavioral output. The principles that govern the circuitry specified by Fru(M) expression might also operate in subcortical networks that govern innate behaviors in mammals.

    View details for DOI 10.1016/j.tins.2006.06.006

    View details for Web of Science ID 000240184400003

    View details for PubMedID 16806511

  • Male-specific fruitless specifies the neural substrates of Drosophila courtship behaviour NATURE Manoli, D. S., Foss, M., Villella, A., Taylor, B. J., Hall, J. C., Baker, B. S. 2005; 436 (7049): 395-400

    Abstract

    Robust innate behaviours are attractive systems for genetically dissecting how environmental cues are perceived and integrated to generate complex behaviours. During courtship, Drosophila males engage in a series of innate, stereotyped behaviours that are coordinated by specific sensory cues. However, little is known about the specific neural substrates mediating this complex behavioural programme. Genetic, developmental and behavioural studies have shown that the fruitless (fru) gene encodes a set of male-specific transcription factors (FruM) that act to establish the potential for courtship in Drosophila. FruM proteins are expressed in approximately 2% of central nervous system neurons, at least one subset of which coordinates the component behaviours of courtship. Here we have inserted the yeast GAL4 gene into the fru locus by homologous recombination and show that (1) FruM is expressed in subsets of all peripheral sensory systems previously implicated in courtship, (2) inhibition of FruM function in olfactory system components reduces olfactory-dependent changes in courtship behaviour, (3) transient inactivation of all FruM-expressing neurons abolishes courtship behaviour, with no other gross changes in general behaviour, and (4) 'masculinization' of FruM-expressing neurons in females is largely sufficient to confer male courtship behaviour. Together, these data demonstrate that FruM proteins specify the neural substrates of male courtship.

    View details for DOI 10.1038/nature03859

    View details for Web of Science ID 000230623400043

    View details for PubMedID 15959468

  • Allocation and specification of the genital disc precursor cells in Drosophila DEVELOPMENTAL BIOLOGY Chen, E. H., Christiansen, A. E., Baker, B. S. 2005; 281 (2): 270-285

    Abstract

    The adult structures of Drosophila melanogaster are derived from larval imaginal discs, which originate as clusters of cells within the embryonic ectoderm. The genital imaginal disc is composed of three primordia (female genital, male genital, and anal primordia) that originate from the embryonic tail segments A8, A9, and A10, respectively, and produce the sexually dimorphic genitalia and analia. We show that the genital disc precursor cells (GDPCs) are first detectable during mid-embryogenesis as a 22-cell cluster in the ventral epidermis. Analysis of mutant and double mutant phenotypes of embryonic patterning genes in the GDPCs, together with their expression patterns in these cells, revealed the following with respect to the origins and specification of the GDPCs. The allocation of the GDPCs from the ventral epidermis requires the function of ventral patterning genes, including the EGF receptor and the spitz group of genes. The ventral localization of the GDPCs is further restricted by the action of dorsal patterning genes. Along the anterior-posterior axis, several segment polarity genes (wingless, engrailed, hedgehog, and patched) are required for the proper allocation of the GDPCs. These segment polarity genes are expressed in some, but not all of the GDPCs, indicating that anterior and posterior compartments are not fully established in the GDPCs. In addition, we found that the three primordia of the larval genital disc have already been specified in the GDPCs by the coordinated actions of the homeotic (Hox) genes, abdominal-A, Abdominal-B, and caudal. By identifying how these different patterning networks regulate the allocation and primordial organization of the 22 embryonic precursors of the compound genital disc, we demonstrate that at least some of the organization of the larval disc originates as positional information in the embryo, thus providing a context for further studies on the development of the genital disc.

    View details for DOI 10.1016/j.ydbio.2005.02.032

    View details for Web of Science ID 000229311600010

    View details for PubMedID 15893978

  • Functional conservation and divergence of intersex, a gene required for female differentiation in Drosophila melanogaster DEVELOPMENT GENES AND EVOLUTION Siegal, M. L., Baker, B. S. 2005; 215 (1): 1-12

    Abstract

    In Drosophila melanogaster, somatic sexual differentiation is regulated by a well characterized genetic hierarchy, by which the ratio of X chromosomes to autosomes (X:A) ultimately directs the deployment of sex-specific transcription factors encoded by doublesex (dsx) and fruitless (fru). In other dipterans, the X:A ratio is not the primary sex-determination signal. Correspondingly, the Drosophila hierarchy is not fully conserved. In all non-drosophilid fly species examined, Sex-lethal (Sxl), the master switch at the top of the Drosophila hierarchy, does not control somatic sex. This rapid divergence contrasts with the apparently deep conservation of dsx, which in Drosophila controls virtually all aspects of somatic sex except for male courtship behavior (which is controlled by fru). Sex-specific dsx mRNAs have been reported in Diptera, Lepidoptera and Hymenoptera, and dsx homologs in nematodes and mammals are required for aspects of male differentiation. Thus, it seems that the bottom of the hierarchy is rather ancient, especially compared with the top. To test this, we cloned insect and vertebrate homologs of the Drosophila gene intersex (ix), which functions together with dsx at the bottom of the hierarchy in females. When expressed in D. melanogaster females mutant at the endogenous ix gene, dipteran and lepidopteran ix homologs restore proper sexual differentiation, substantiating the hypothesis that ix, like dsx, is broadly conserved. When the mouse homolog is expressed it produces a dominant-negative phenotype suggesting partial functional divergence. Our results raise the possibility that a functional association between ix- and dsx-related gene products existed before the origin of the bifunctional dsx gene used in insect sex determination.

    View details for DOI 10.1007/s00427-004-0445-x

    View details for Web of Science ID 000226302500001

    View details for PubMedID 15645316

  • X chromosome sites autonomously recruit the dosage compensation complex in Drosophila males PLOS BIOLOGY Fagegaltier, D., Baker, B. S. 2004; 2 (11): 1854-1861

    Abstract

    It has been proposed that dosage compensation in Drosophila males occurs by binding of two core proteins, MSL-1 and MSL-2, to a set of 35-40 X chromosome "entry sites" that serve to nucleate mature complexes, termed compensasomes, which then spread to neighboring sequences to double expression of most X-linked genes. Here we show that any piece of the X chromosome with which compensasomes are associated in wild-type displays a normal pattern of compensasome binding when inserted into an autosome, independently of the presence of an entry site. Furthermore, in chromosomal rearrangements in which a piece of X chromosome is inserted into an autosome, or a piece of autosome is translocated to the X chromosome, we do not observe spreading of compensasomes to regions of autosomes that have been juxtaposed to X chromosomal material. Taken together these results suggest that spreading is not involved in dosage compensation and that nothing distinguishes an entry site from the other X chromosome sites occupied by compensasomes beyond their relative affinities for compensasomes. We propose a new model in which the distribution of compensasomes along the X chromosome is achieved according to the hierarchical affinities of individual binding sites.

    View details for DOI 10.1371/journal.pbio.0020341

    View details for Web of Science ID 000225160300016

    View details for PubMedID 15502872

  • Median bundle neurons coordinate behaviours during Drosophila male courtship NATURE Manoli, D. S., Baker, B. S. 2004; 430 (6999): 564-569

    Abstract

    Throughout the animal kingdom the innate nature of basic behaviour routines suggests that the underlying neuronal substrates necessary for their execution are genetically determined and developmentally programmed. Complex innate behaviours require proper timing and ordering of individual component behaviours. In Drosophila melanogaster, analyses of combinations of mutations of the fruitless (fru) gene have shown that male-specific isoforms (Fru(M)) of the Fru transcription factor are necessary for proper execution of all steps of the innate courtship ritual. Here, we eliminate Fru(M) expression in one group of about 60 neurons in the Drosophila central nervous system and observe severely contracted courtship behaviour, including rapid courtship initiation, absence of orienting and tapping, and the simultaneous occurrence of wing vibration, licking and attempted copulation. Our results identify a small group of median bundle neurons, that in wild-type Drosophila appropriately trigger the sequential execution of the component behaviours that constitute the Drosophila courtship ritual.

    View details for DOI 10.1038/nature02713

    View details for Web of Science ID 000222946100049

    View details for PubMedID 15282607

  • A genomic analysis of Drosophila somatic sexual differentiation and its regulation DEVELOPMENT Arbeitman, M. N., Fleming, A. A., Siegal, M. L., Null, B. H., Baker, B. S. 2004; 131 (9): 2007-2021

    Abstract

    In virtually all animals, males and females are morphologically, physiologically and behaviorally distinct. Using cDNA microarrays representing one-third of Drosophila genes to identify genes expressed sex-differentially in somatic tissues, we performed an expression analysis on adult males and females that: (1) were wild type; (2) lacked a germline; or (3) were mutant for sex-determination regulatory genes. Statistical analysis identified 63 genes sex-differentially expressed in the soma, 20 of which have been confirmed by RNA blots thus far. In situ hybridization experiments with 11 of these genes showed they were sex-differentially expressed only in internal genital organs. The nature of the products these genes encode provides insight into the molecular physiology of these reproductive tissues. Analysis of the regulation of these genes revealed that their adult expression patterns are specified by the sex hierarchy during development, and that doublesex probably functions in diverse ways to set their activities.

    View details for Web of Science ID 000221663600012

    View details for PubMedID 15056610

  • intersex, a gene required for female sexual development in Drosophila, is expressed in both sexes and functions together with doublesex to regulate terminal differentiation DEVELOPMENT Garrett-Engele, C. M., Siegal, M. L., Manoli, D. S., Williams, B. C., Li, H., Baker, B. S. 2002; 129 (20): 4661-4675

    Abstract

    Previous genetic studies indicated intersex (ix) functions only in females and that it acts near the end of the sex determination hierarchy to control somatic sexual differentiation in Drosophila melanogaster. We have cloned ix and characterized its function genetically, molecularly and biochemically. The ix pre-mRNA is not spliced, and ix mRNA is produced in both sexes. The ix gene encodes a 188 amino acid protein, which has a sequence similar to mammalian proteins thought to function as transcriptional activators, and a Caenorhabditis elegans protein that is thought to function as a transcription factor. Bringing together the facts that (1) the ix phenotype is female-specific and (2) functions at the end of the sex determination hierarchy, yet (3) is expressed sex non-specifically and appears likely to encode a transcription factor with no known DNA-binding domain, leads to the inference that ix may require the female-specific protein product of the doublesex (dsx) gene in order to function. Consistent with this inference, we find that for all sexually dimorphic cuticular structures examined, ix and dsx are dependent on each other to promote female differentiation. This dependent relationship also holds for the only known direct target of dsx, the Yolk protein (Yp) genes. Using yeast 2-hybrid assay, immunoprecipitation of recombinant tagged IX and DSX proteins from Drosophila S2 cell extracts, and gel shifts with the tagged IX and DSX(F) proteins, we demonstrate that IX interacts with DSX(F), but not DSX(M). Taken together, the above findings strongly suggest that IX and DSX(F) function in a complex, in which IX acts as a transcriptional co-factor for the DNA-binding DSX(F).

    View details for Web of Science ID 000179000300001

    View details for PubMedID 12361959

  • Sex comes in from the cold: the integration of sex and pattern TRENDS IN GENETICS Christiansen, A. E., Keisman, E. L., Ahmad, S. M., Baker, B. S. 2002; 18 (10): 510-516

    Abstract

    There has recently been a revolution in our understanding of how the Drosophila sex-determination hierarchy generates somatic sexual dimorphism. Most significantly, the sex hierarchy has been shown to modulate the activities of well-known signaling molecules (FGF, Wnt and TGF beta proteins) and transcription factors (BAB and DAC) to direct various sex-specific aspects of growth and differentiation. As some of the genes encoding these proteins are also the targets of Hox gene action, these and other findings are revealing the levels at which the sex determination and Hox patterning pathways are integrated to control growth, morphogenesis and differentiation.

    View details for Web of Science ID 000178296400006

    View details for PubMedID 12350340

  • Gene expression during the life cycle of Drosophila melanogaster SCIENCE Arbeitman, M. N., Furlong, E. E., Imam, F., JOHNSON, E., Null, B. H., Baker, B. S., Krasnow, M. A., Scott, M. P., Davis, R. W., White, K. P. 2002; 297 (5590): 2270-2275

    Abstract

    Molecular genetic studies of Drosophila melanogaster have led to profound advances in understanding the regulation of development. Here we report gene expression patterns for nearly one-third of all Drosophila genes during a complete time course of development. Mutations that eliminate eye or germline tissue were used to further analyze tissue-specific gene expression programs. These studies define major characteristics of the transcriptional programs that underlie the life cycle, compare development in males and females, and show that large-scale gene expression data collected from whole animals can be used to identify genes expressed in particular tissues and organs or genes involved in specific biological and biochemical processes.

    View details for Web of Science ID 000178222000050

    View details for PubMedID 12351791

  • Sex-specific deployment of FGF signaling in Drosophila recruits mesodermal cells into the male genital imaginal disc CELL Ahmad, S. M., Baker, B. S. 2002; 109 (5): 651-661

    Abstract

    A central issue in developmental biology is how the deployment of generic signaling proteins produces diverse specific outcomes. We show that Drosophila FGF is used, only in males, to recruit mesodermal cells expressing its receptor to become part of the genital imaginal disc. Male-specific deployment of FGF signaling is controlled by the sex determination regulatory gene doublesex. The recruited mesodermal cells become epithelial and differentiate into parts of the internal genitalia. Our results provide exceptions to two basic tenets of imaginal disc biology-that imaginal disc cells are derived from the embryonic ectoderm and belong to either an anterior or posterior compartment. The recruited mesodermal cells migrate into the disc late in development and are neither anterior nor posterior.

    View details for Web of Science ID 000175957900013

    View details for PubMedID 12062107

  • Molecular genetic dissection of the sex-specific and vital functions of the Drosophila melanogaster sex determination gene fruitless GENETICS Anand, A., Villella, A., Ryner, L. C., Carlo, T., Goodwin, S. F., Song, H. J., Gailey, D. A., MORALES, A., Hall, J. C., Baker, B. S., Taylor, B. J. 2001; 158 (4): 1569-1595

    Abstract

    A multibranched hierarchy of regulatory genes controls all aspects of somatic sexual development in Drosophila melanogaster. One branch of this hierarchy is headed by the fruitless (fru) gene and functions in the central nervous system, where it is necessary for male courtship behavior as well as the differentiation of a male-specific abdominal structure, the muscle of Lawrence (MOL). A preliminary investigation of several of the mutations described here showed that the fru gene also has a sex-nonspecific vital function. The fru gene produces a complex set of transcripts through the use of four promoters and alternative splicing. Only the primary transcripts produced from the most distal (P1) promoter are sex-specifically spliced under direction of the sex-determination hierarchy. We have analyzed eight new fru mutations, created by X-ray mutagenesis and P-element excision, to try to gain insight into the relationship of specific transcript classes to specific fru functions. Males that lack the P1-derived fru transcripts show a complete absence of sexual behavior, but no other defects besides the loss of the MOL. Both males and females that have reduced levels of transcripts from the P3 promoter develop into adults but frequently die after failing to eclose. Analysis of the morphology and behavior of adult escapers showed that P3-encoded functions are required for the proper differentiation and eversion of imaginal discs. Furthermore, the reduction in the size of the neuromuscular junctions on abdominal muscles in these animals suggests that one of fru's sex-nonspecific functions involves general aspects of neuronal differentiation. In mutants that lack all fru transcripts as well as a small number of adjacent genes, animals die at an early pupal stage, indicating that fru's function is required only during late development. Thus, fru functions both in the sex-determination regulatory hierarchy to control male sexual behavior through sex-specific transcripts and sex-nonspecifically to control the development of imaginal discs and motorneuronal synapses during adult development through sex-nonspecific transcript classes.

    View details for Web of Science ID 000170603700016

    View details for PubMedID 11514448

  • The sex determination gene doublesex regulates the A/P organizer to direct sex-specific patterns of growth in the Drosophila genital imaginal disc DEVELOPMENTAL CELL Keisman, E. L., Christiansen, A. E., Baker, B. S. 2001; 1 (2): 215-225

    Abstract

    Each Drosophila genital imaginal disc contains primordia for both male and female genitalia and analia. The sexually dimorphic development of this disc is governed by the sex-specific expression of doublesex (dsx). We present data that substantially revises our understanding of how dsx controls growth and differentiation in the genital disc. The classical view of genital disc development is that in each sex, dsx autonomously "represses" the development of the inappropriate genital primordium while allowing the development of the appropriate primordium. Instead, we show that dsx regulates the A/P organizer to control growth of each genital primordium, and then directs each genital primordium to differentiate defined adult structures in both sexes.

    View details for Web of Science ID 000175301300009

    View details for PubMedID 11702781

  • The Drosophila sex determination hierarchy modulates wingless and decapentaplegic signaling to deploy dachshund sex-specifically in the genital imaginal disc DEVELOPMENT Keisman, E. L., Baker, B. S. 2001; 128 (9): 1643-1656

    Abstract

    The integration of multiple developmental cues is crucial to the combinatorial strategies for cell specification that underlie metazoan development. In the Drosophila genital imaginal disc, which gives rise to the sexually dimorphic genitalia and analia, sexual identity must be integrated with positional cues, in order to direct the appropriate sexually dimorphic developmental program. Sex determination in Drosophila is controlled by a hierarchy of regulatory genes. The last known gene in the somatic branch of this hierarchy is the transcription factor doublesex (dsx); however, targets of the hierarchy that play a role in sexually dimorphic development have remained elusive. We show that the gene dachshund (dac) is differentially expressed in the male and female genital discs, and plays sex-specific roles in the development of the genitalia. Furthermore, the sex determination hierarchy mediates this sex-specific deployment of dac by modulating the regulation of dac by the pattern formation genes wingless (wg) and decapentaplegic (dpp). We find that the sex determination pathway acts cell-autonomously to determine whether dac is activated by wg signaling, as in females, or by dpp signaling, as in males.

    View details for Web of Science ID 000168802300015

    View details for PubMedID 11290302

  • Are complex behaviors specified by dedicated regulatory genes? Reasoning from Drosophila CELL Baker, B. S., Taylor, B. J., Hall, J. C. 2001; 105 (1): 13-24

    View details for Web of Science ID 000168063300004

    View details for PubMedID 11300999

  • Origin and evolution of the regulatory gene male-specific lethal-3 MOLECULAR BIOLOGY AND EVOLUTION Marin, I., Baker, B. S. 2000; 17 (8): 1240-1250

    Abstract

    Dosage compensation in Drosophila is mediated by genes known as "male-specific lethals" (msls). Several msls, including male-specific lethal-3 (msl-3), encode proteins of unknown function. We cloned the Drosophila virilis msl-3 gene. Using the information provided by the sequences of the Drosophila melanogaster and D. virilis genes, we found that sequences of other species can be aligned along their entire lengths with msl-3. Among them, there are genes in yeasts (the Schizosaccharomyces pombe Alp13 gene, as well as a putative Alp13 homolog, found in Saccharomyces cerevisae) and in mammals (MRG15 and MSL3L1 and their relatives) plus uncharacterized sequences of the nematode Caenorhabditis elegans and the plants Arabidopsis thaliana, Lycopersicon esculentum, and Zea mays. A second Drosophila gene of this family has also been found. It is thus likely that msl-3-like genes are present in all eukaryotes. Phylogenetic analyses suggest that msl-3 is orthologous to the mammalian MSL3L1 genes, while the second Drosophila melanogaster gene (which we have called Dm MRG15) is orthologous to mammalian MRG15. These analyses also suggest that the msl-3/MRG15 duplication occurred after the fungus/animal split, while an independent duplication occurred in plants. The proteins encoded by these genes have similar structures, including a putative chromodomain close to their N-terminal end and a putative leucine zipper at their C-terminus. The possible functional roles of these proteins are discussed.

    View details for Web of Science ID 000088720000012

    View details for PubMedID 10908644

  • Dosage compensation rox! CURRENT OPINION IN CELL BIOLOGY Franke, A., Baker, B. S. 2000; 12 (3): 351-354

    Abstract

    Recent advances in our understanding of dosage compensation in flies have centered on characterizing its sex-specificity, identifying the structural RNAs involved in the process, and determining how dosage compensation is targeted to particular sites on the X chromosome.

    View details for Web of Science ID 000087138200013

    View details for PubMedID 10801462

  • The rox1 and rox2 RNAs are essential components of the compensasome, which mediates dosage compensation in Drosophila MOLECULAR CELL Franke, A., Baker, B. S. 1999; 4 (1): 117-122

    Abstract

    The rox1 and rox2 RNAs have been suggested to be components of the dosage compensation machinery in Drosophila. We show that both rox RNAs colocalize with the male-specific lethal proteins at hundreds of specific bands along the male X chromosome. The rox RNAs and MSL proteins also colocalize with the X chromosome in all somatic cells and are expressed in the same temporal pattern throughout development. Genetic analysis shows that the functions of the rox genes are redundant and required for the association of the MSL proteins with the male X chromosome. These data provide compelling evidence for a direct function of the rox RNAs in dosage compensation.

    View details for Web of Science ID 000081669300012

    View details for PubMedID 10445033

  • The evolutionary dynamics of sex determination SCIENCE Marin, I., Baker, B. S. 1998; 281 (5385): 1990-1994

    Abstract

    REVIEW There is substantial cytogenetic data indicating that the process of sex determination can evolve relatively rapidly. However, recent molecular studies on the evolution of the regulatory genes that control sex determination in the insect Drosophila melanogaster, the nematode Caenorhabditis elegans, and mammals suggest that, although certain sex determination regulatory genes have evolved relatively rapidly, other sex determination regulatory genes are quite conserved. Thus, studies of the evolution of sex determination, a process that appears to have elements that undergo substantial evolutionary change and others that may be conserved, could provide substantial insights into the kinds of forces that both drive and constrain the evolution of developmental hierarchies.

    View details for Web of Science ID 000076161800046

    View details for PubMedID 9748152

  • hermaphrodite and doublesex function both dependently and independently to control various aspects of sexual differentiation in Drosophila DEVELOPMENT Li, H., Baker, B. S. 1998; 125 (14): 2641-2651

    Abstract

    The hermaphrodite (her) gene is necessary for sexual differentiation in Drosophila. Our characterization of her's zygotic function suggests that one set of female-specific terminal differentiation genes, the yolk protein (yp) genes, is transcriptionally activated by two separate pathways. One is a female-specific pathway, which is positively regulated by the female-specific doublesex protein (DSXF). The other is a non-sex-specific pathway, that is positively regulated by HER. The HER pathway is prevented from functioning in males by the action of the male-specific doublesex protein (DSXM). The HER and DSX pathways also function independently to control downstream target genes in the precursor cells that give rise to the vaginal teeth and dorsal anal plate of females, and the lateral anal plates of males. However, a female-specific pathway that is dependent on both DSXF and HER controls the female-specific differentiation of the foreleg bristles and tergites 5 and 6, and the male-specific differentiation of these tissues does not require the suppression of HER's function by DSXM.

    View details for Web of Science ID 000075365000011

    View details for PubMedID 9636079

  • Regulation of sex-specific selection of fruitless 5 ' splice sites by transformer and transformer-2 MOLECULAR AND CELLULAR BIOLOGY Heinrichs, V., Ryner, L. C., Baker, B. S. 1998; 18 (1): 450-458

    Abstract

    In Drosophila melanogaster, the fruitless (fru) gene controls essentially all aspects of male courtship behavior. It does this through sex-specific alternative splicing of the fru pre-mRNA, leading to the production of male-specific fru mRNAs capable of expressing male-specific fru proteins. Sex-specific fru splicing involves the choice between alternative 5' splice sites, one used exclusively in males and the other used only in females. Here we report that the Drosophila sex determination genes transformer (tra) and transformer-2 (tra-2) switch fru splicing from the male-specific pattern to the female-specific pattern through activation of the female-specific fru 5' splice site. Activation of female-specific fru splicing requires cis-acting tra and tra-2 repeat elements that are part of an exonic splicing enhancer located immediately upstream of the female-specific fru 5' splice site and are recognized by the TRA and TRA-2 proteins in vitro. This fru splicing enhancer is sufficient to promote the activation by tra and tra-2 of both a 5' splice site and the female-specific doublesex (dsx) 3' splice site, suggesting that the mechanisms of 5' splice site activation and 3' splice site activation may be similar.

    View details for Web of Science ID 000071195700046

    View details for PubMedID 9418892

  • her, a gene required for sexual differentiation in Drosophila, encodes a zinc finger protein with characteristics of ZFY-like proteins and is expressed independently of the sex determination hierarchy DEVELOPMENT Li, H., Baker, B. S. 1998; 125 (2): 225-235

    Abstract

    The zygotic function of the hermaphrodite (her) gene of Drosophila plays an important role in sexual differentiation. Our molecular genetic characterization of her suggests that her is expressed sex non-specifically and independently of other known sex determination genes and that it acts together with the last genes in the sex determination hierarchy, doublesex and intersex, to control female sexual differentiation. Consistent with such a terminal function in sexual differentiation, her encodes a protein with C2H2-type zinc fingers. The her zinc fingers are atypical and similar to the even-numbered zinc fingers of ZFY and ZFX proteins in humans and other vertebrates.

    View details for Web of Science ID 000072046900008

    View details for PubMedID 9486796

  • The regulation of the Drosophila msl-2 gene reveals a function for Sex-lethal in translational control CELL Bashaw, G. J., Baker, B. S. 1997; 89 (5): 789-798

    Abstract

    In Drosophila, dosage compensation occurs by increasing the transcription of the single male X chromosome. Four trans-acting factors encoded by the male-specific lethal genes are required for this process. Dosage compensation is restricted to males by the splicing regulator Sex-lethal, which functions to prevent the production of the MSL-2 protein in females by an unknown mechanism. In this report, we provide evidence that Sex-lethal acts synergistically through sequences in both the 5' and 3' untranslated regions of MSL-2 to mediate repression. We also provide evidence that the repression of MSL-2 is directly regulated by Sex-lethal at the level of translation.

    View details for Web of Science ID A1997XB92500016

    View details for PubMedID 9182767

  • In vivo analysis of the functional domains of the Drosophila splicing regulator RBP1 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Heinrichs, V., Baker, B. S. 1997; 94 (1): 115-120

    Abstract

    The Drosophila splicing factor RBP1 participates together with TRA and TRA-2 in the regulation of alternative splicing of doublesex (dsx) pre-mRNA. It does so by recognizing RBP1 RNA target sequences in the dsx pre-mRNA. RBP1 belongs to the Ser-Arg-rich (SR) protein family of splicing factors, which have in common a N-terminal RNA recognition motif-type RNA binding domain, a Gly-rich region, and a C-terminal SR domain. Using a tissue culture transfection assay, we demonstrate that the Gly residues within the Gly-rich domain, the ribonucleoprotein motifs within the RNA recognition motif RNA binding domain, and the SR domain are required for regulation of dsx splicing by RBP1 in vivo. Furthermore, using a two-hybrid system, we show protein-protein interactions between RBP1 and itself and between RBP1 and TRA-2. The SR domain and the Gly residues within the Gly-rich domain of RBP1 were found to be involved in these protein-protein interactions. Our results suggest that RBP1 and TRA-2 function in regulation of dsx splicing by forming a complex.

    View details for Web of Science ID A1997WC34700022

    View details for PubMedID 8990170

  • Compartmental organization of the Drosophila genital imaginal discs DEVELOPMENT Chen, E. H., Baker, B. S. 1997; 124 (1): 205-218

    Abstract

    We have investigated the anterior and posterior compartmental organization of the genital imaginal disc. Unlike the thoracic discs, the genital disc is a compound disc consisting of three primordia--the female genital, male genital, and anal primordia. Here we provide evidence that each primordium is divided into anterior and posterior compartments. Genes that are known to be expressed in compartment-specific manners in other discs (engrailed, hedgehog, patched, decapentaplegic, wingless and cubitus interruptus) are expressed in analogous patterns in each primordium of the genital disc. Specifically, engrailed and cubitus interruptus are expressed in complementary domains, while patched, decapentaplegic and wingless are expressed along the border between the two domains. Mitotic clones induced at the beginning of the second larval instar do not cross the boundary between the engrailed-expressing and cubitus interruptus-expressing domains, indicating that these domains are true genetic compartments. Furthermore, we examined the phenotypes of mutant clones of the cAMP-dependent protein kinase A and engrailed-invected, genes that are known to play compartment-specific functions in other discs. These experiments demonstrate that the anterior/posterior patterning functions of these genes are conserved in the genital disc. The adult clonal phenotypes of protein kinase A and engrailed-invected mutants also provide a more detailed map of the adult genitalia and analia with respect to the anterior/posterior compartmental subdivision. Our results lead us to propose a new model to describe the anterior and posterior compartmental organization of the genital disc.

    View details for Web of Science ID A1997WE50100020

    View details for PubMedID 9006081

  • Control of male sexual behavior and sexual orientation in Drosophila by the fruitless gene CELL Ryner, L. C., Goodwin, S. F., Castrillon, D. H., Anand, A., Villella, A., Baker, B. S., Hall, J. C., Taylor, B. J., Wasserman, S. A. 1996; 87 (6): 1079-1089

    Abstract

    Sexual orientation and courtship behavior in Drosophila are regulated by fruitless (fru), the first gene in a branch of the sex-determination hierarchy functioning specifically in the central nervous system (CNS). The phenotypes of new fru mutants encompass nearly all aspects of male sexual behavior. Alternative splicing of fru transcripts produces sex-specific proteins belonging to the BTB-ZF family of transcriptional regulators. The sex-specific fru products are produced in only about 500 of the 10(5) neurons that comprise the CNS. The properties of neurons expressing these fru products suggest that fru specifies the fates or activities of neurons that carry out higher order control functions to elicit and coordinate the activities comprising male courtship behavior.

    View details for Web of Science ID A1996VY44700013

    View details for PubMedID 8978612

  • The dosage compensation system of Drosophila is co-opted by newly evolved X chromosomes NATURE Marin, I., Franke, A., Bashaw, G. J., Baker, B. S. 1996; 383 (6596): 160-163

    Abstract

    In species where males and females differ in number of sex chromosomes, the expression of sex-linked genes is equalized by a process known as dosage compensation. In Drosophila melanogaster, dosage compensation is mediated by the binding of the products of the male-specific lethal (msl) genes to the single male X chromosome. Here we report that the sex- and chromosome-specific binding of three of the msl proteins (MSLs) occurs in other drosophilid species, spanning four genera. Moreover, we show that MSL binding correlates with the evolution of the sex chromosomes: in species that have acquired a second X chromosome arm because of an X-autosome translocation, we observe binding of the MSLs to the 'new' (previously autosomal) arm of the X chromosome, only when its homologue has degenerated. Moreover, in Drosophila miranda, a Y-autosome translocation has produced a new X chromosome (called neo-X), only some regions of which are dosage compensated. In this neo-X chromosome, the pattern of MSL binding correlates with the known pattern of dosage compensation.

    View details for Web of Science ID A1996VG14800049

    View details for PubMedID 8774878

  • Evidence that MSL-mediated dosage compensation in Drosophila begins at blastoderm DEVELOPMENT Franke, A., Dernburg, A., Bashaw, G. J., Baker, B. S. 1996; 122 (9): 2751-2760

    Abstract

    In Drosophila equalization of the amounts of gene products produced by X-linked genes in the two sexes is achieved by hypertranscription of the single male X chromosome. This process, dosage compensation, is controlled by a set of male-specific lethal (msl) genes, that appear to act at the level of chromatin structure. The properties of the MSL proteins have been extensively studied in the polytene salivary gland chromosomes where they bind to the same set of sites along the male X chromosome in a co-dependent manner. Here we report experiments that show that the MSL proteins first associate with the male X chromosome as early as blastoderm stage, slightly earlier than the histone H4 isoform acetylated at lysine 16 is detected on the X chromosome. MSL binding to the male X chromosome is observed in all somatic tissues of embryos and larvae. Binding of the MSLs to the X chromosome is also interdependent in male embryos and prevented in female embryos by the expression of Sex-lethal (Sxl). A delayed onset of binding of the MSLs in male progeny of homozygous mutant msl-1 or mle mothers coupled with the previous finding that such males have an earlier lethal phase supports the idea that msl-mediated dosage compensation begins early in embryogenesis. Other results show that the maleless (MLE) protein on embryo and larval chromosomes differs in its reactivity with antibodies; the functional significance of this finding remains to be explored.

    View details for Web of Science ID A1996VJ07500018

    View details for PubMedID 8787749

  • Dosage compensation and chromatin structure in Drosophila CURRENT OPINION IN GENETICS & DEVELOPMENT Bashaw, G. J., Baker, B. S. 1996; 6 (4): 496-501

    Abstract

    The past year has brought significant advances in our understanding of the male-specific lethal (msl genes and dosage compensation in Drosophila. The molecular characterization of the msl-2 gene has, to a great extent, solved the question of how msl-mediated dosage compensation is restricted to males. Molecular analyses of the msl genes have substantiated the proposal that the MSL proteins function as a multimeric complex to mediate dosage compensation. The finding that MSL-2 protein has a RING finger and the demonstration that an insulator protein facilitates the dosage compensation of X-linked genes inserted into the autosomes have opened promising avenues to identify the cis-acting dosage-compensation determinants.

    View details for Web of Science ID A1996VD29200016

    View details for PubMedID 8791531

  • THE MSL-2 DOSAGE COMPENSATION GENE OF DROSOPHILA ENCODES A PUTATIVE DNA-BINDING PROTEIN WHOSE EXPRESSION IS SEX SPECIFICALLY REGULATED BY SEX-LETHAL DEVELOPMENT Bashaw, G. J., Baker, B. S. 1995; 121 (10): 3245-3258

    Abstract

    In Drosophila dosage compensation increases the rate of transcription of the male's X chromosome and depends on four autosomal male-specific lethal genes. We have cloned the msl-2 gene and shown that MSL-2 protein is co-localized with the other three MSL proteins at hundreds of sites along the male polytene X chromosome and that this binding requires the other three MSL proteins. msl-2 encodes a protein with a putative DNA-binding domain: the RING finger. MSL-2 protein is not produced in females and sequences in both the 5' and 3' UTRs are important for this sex-specific regulation. Furthermore, msl-2 pre-mRNA is alternatively spliced in a Sex-lethal-dependent fashion in its 5' UTR.

    View details for Web of Science ID A1995RZ75600012

    View details for PubMedID 7588059

  • THE DROSOPHILA SR PROTEIN RBP1 CONTRIBUTES TO THE REGULATION OF DOUBLESEX ALTERNATIVE SPLICING BY RECOGNIZING RBP1 RNA TARGET SEQUENCES EMBO JOURNAL Heinrichs, V., Baker, B. S. 1995; 14 (16): 3987-4000

    Abstract

    The SR proteins represent a family of splicing factors several of which have been implicated in the regulation of sex-specific alternative splicing of doublesex (dsx) pre-mRNA in Drosophila. The dsx gene is involved in Drosophila sex determination. We have identified two RNA target sequence motifs recognized by the SR protein RBP1 from Drosophila using an in vitro selection approach. Several copies of these RBP1 target sequences were found within two regions of the dsx pre-mRNA which are important for the regulation of dsx alternative splicing, the repeat region and the purine-rich polypyrimidine tract of the regulated female-specific 3' splice site. We show that RBP1 target sequences within the dsx repeat region are required for the efficient splicing of dsx pre-mRNA. Moreover, our studies reveal that RBP1 contributes to the activation of female-specific dsx splicing in vivo by recognizing the RBP1 target sequences within the purine-rich polypyrimidine tract of the female-specific 3' splice site.

    View details for Web of Science ID A1995RQ66900014

    View details for PubMedID 7664738

  • A GENETIC-ANALYSIS OF INTERSEX, A GENE REGULATING SEXUAL-DIFFERENTIATION IN DROSOPHILA-MELANOGASTER FEMALES GENETICS Chase, B. A., Baker, B. S. 1995; 139 (4): 1649-1661

    Abstract

    Sex-type in Drosophila melanogaster is controlled by a hierarchically acting set of regulatory genes. At the terminus of this hierarchy lie those regulatory genes responsible for implementing sexual differentiation: genes that control the activity of target loci whose products give rise to sexually dimorphic phenotypes. The genetic analysis of the intersex (ix) gene presented here demonstrates that ix is such a terminally positioned regulatory locus. The ix locus has been localized to the cytogenetic interval between 47E3-6 and 47F11-18. A comparison of the morphological and behavioral phenotypes of homozygotes and hemizygotes for three point mutations at ix indicates that the null phenotype of ix is to transform diplo-X animals into intersexes while leaving haplo-X animals unaffected. Analysis of X-ray induced, mitotic recombination clones lacking ix+ function in the abdomen of diplo-X individuals indicates that the ix+ product functions in a cell-autonomous manner and that it is required at least until the termination of cell division in this tissue. Taken together with previous analyses, our results indicate that the ix+ product is required to function with the female-specific product of doublesex to implement appropriate female sexual differentiation in diplo-X animals.

    View details for Web of Science ID A1995QN97500016

    View details for PubMedID 7789766

  • MOLECULAR CHARACTERIZATION OF THE MALE-SPECIFIC LETHAL-3 GENE AND INVESTIGATIONS OF THE REGULATION OF DOSAGE COMPENSATION IN DROSOPHILA DEVELOPMENT Gorman, M., Franke, A., Baker, B. S. 1995; 121 (2): 463-475

    Abstract

    In Drosophila, dosage compensation occurs by transcribing the single male X chromosome at twice the rate of each of the two female X chromosomes. This hypertranscription requires four autosomal male-specific lethal (msl) genes and is negatively regulated by the Sxl gene in females. Two of the msls, the mle and msl-1 genes, encode proteins that are associated with hundreds of specific sites along the length of the male X chromosome. MLE and MSL-1 X chromosome binding are negatively regulated by Sxl in females and require the functions of the other msls in males. To investigate further the regulation of dosage compensation and the role of the msls in this process, we have cloned and molecularly characterized another msl, the msl-3 gene. We have found that MSL-3 is also associated with the male X chromosome. We have further investigated whether Sxl negatively regulates MSL-3 X-chromosome binding in females and whether MSL-3 X-chromosome binding requires the other msls. Our results suggest that the MLE, MSL-1 and MSL-3 proteins may associate with one another in a male-specific heteromeric complex on the X chromosome to achieve its hypertranscription.

    View details for Web of Science ID A1995QK89600018

    View details for PubMedID 7768187

  • THE DUAL ROLE OF HERMAPHRODITE IN THE DROSOPHILA SEX DETERMINATION REGULATORY HIERARCHY DEVELOPMENT Pultz, M. A., Baker, B. S. 1995; 121 (1): 99-111

    Abstract

    The hermaphrodite (her) locus has both maternal and zygotic functions required for normal female development in Drosophila. Maternal her function is needed for the viability of female offspring, while zygotic her function is needed for female sexual differentiation. Here we focus on understanding how her fits into the sex determination regulatory hierarchy. Maternal her function is needed early in the hierarchy: genetic interactions of her with the sisterless genes (sis-a and sis-b), with function-specific Sex-lethal (Sxl) alleles and with the constitutive allele SxlM#1 suggest that maternal her function is needed for Sxl initiation. When mothers are defective for her function, their daughters fail to activate a reporter gene for the Sxl early promoter and are deficient in Sxl protein expression. Dosage compensation is misregulated in the moribund daughters: some salivary gland cells show binding of the maleless (mle) dosage compensation regulatory protein to the X chromosome, a binding pattern normally seen only in males. Thus maternal her function is needed early in the hierarchy as a positive regulator of Sxl, and the maternal effects of her on female viability probably reflect Sxl's role in regulating dosage compensation. In contrast to her's maternal function, her's zygotic function in sex determination acts at the end of the hierarchy. This zygotic effect is not rescued by constitutive Sxl expression, nor by constitutive transformer (tra) expression. Moreover, the expression of doublesex (dsx) transcripts appears normal in her mutant females. We conclude that the maternal and zygotic functions of her are needed at two distinctly different levels of the sex determination regulatory hierarchy.

    View details for Web of Science ID A1995QD18500010

    View details for PubMedID 7867511

  • HOW FLIES MAKE ONE EQUAL 2 - DOSAGE COMPENSATION IN DROSOPHILA TRENDS IN GENETICS Gorman, M., Baker, B. S. 1994; 10 (10): 376-380

    Abstract

    Dosage compensation is the process by which the expression of X-linked genes is equalized in males and females. In Drosophila, dosage compensation occurs by coordinately upregulating the transcription rates of all the genes on the single X chromosome in males. This hypertranscription requires the functioning of four autosomal male-specific lethal (msl) genes and is under the control of the Sxl gene. Recent genetic and molecular studies have suggested that the msl proteins may associate with one another in a sex-specific heteromeric complex on the male X chromosome, where they may function to alter its chromatin structure.

    View details for Web of Science ID A1994PJ03900012

    View details for PubMedID 7985243

  • A GENETIC-ANALYSIS OF HERMAPHRODITE, A PLEIOTROPIC SEX DETERMINATION GENE IN DROSOPHILA-MELANOGASTER GENETICS Pultz, M. A., Carson, G. S., Baker, B. S. 1994; 136 (1): 195-207

    Abstract

    Sex determination in Drosophila is controlled by a cascade of regulatory genes. Here we describe hermaphrodite (her), a new component of this regulatory cascade with pleiotropic zygotic and maternal functions. Zygotically, her+ function is required for female sexual differentiation: when zygotic her+ function is lacking, females are transformed to intersexes. Zygotic her+ function may also play a role in male sexual differentiation. Maternally, her+ function is needed to ensure the viability of female progeny: a partial loss of her+ function preferentially kills daughters. In addition, her has both zygotic and maternal functions required for viability in both sexes. Temperature sensitivity prevails for all known her alleles and for all of the her phenotypes described above, suggesting that her may participate in an intrinsically temperature-sensitive process. This analysis of four her alleles also indicates that the zygotic and maternal components of of her function are differentially mutable. We have localized her cytologically to 36A3-36A11.

    View details for Web of Science ID A1994MP22200018

    View details for PubMedID 8138157

  • DOSAGE COMPENSATION IN DROSOPHILA ANNUAL REVIEW OF GENETICS Baker, B. S., Gorman, M., Marin, I. 1994; 28: 491-521

    View details for Web of Science ID A1994PY64400022

    View details for PubMedID 7893138

  • SEX-LETHAL, MASTER AND SLAVE - A HIERARCHY OF GERM-LINE SEX DETERMINATION IN DROSOPHILA DEVELOPMENT Oliver, B., Kim, Y. J., Baker, B. S. 1993; 119 (3): 897-908

    Abstract

    Female sex determination in the germ line of Drosophila melanogaster is regulated by genes functioning in the soma as well as genes that function within the germ line. Genes known or suspected to be involved in germ-line sex determination in Drosophila melanogaster have been examined to determine if they are required upstream or downstream of Sex-lethal+, a known germ-line sex determination gene. Seven genes required for female-specific splicing of germ-line Sex-lethal+ pre-mRNA are identified. These results together with information about the tissues in which these genes function and whether they control sex determination and viability or just sex determination in the germ line have been used to deduce the genetic hierarchy regulating female germ-line sex determination. This hierarchy includes the somatic sex determination genes transformer+, transformer-2+ and doublesex+ (and by inference Sex-lethal+), which control a somatic signal required for female germ-line sex determination, and the germ-line ovarian tumor genes fused+, ovarian tumor+, ovo+, sans fille+, and Sex-lethal+, which are involved in either the reception or interpretation of this somatic sex determination signal. The fused+, ovarian tumor+, ovo+ and sans fille+ genes function upstream of Sex-lethal+ in the germ line.

    View details for Web of Science ID A1993MH94500027

    View details for PubMedID 8187645

  • THE DROSOPHILA GENE RBP9 ENCODES A PROTEIN THAT IS A MEMBER OF A CONSERVED GROUP OF PUTATIVE RNA-BINDING PROTEINS THAT ARE NERVOUS-SYSTEM SPECIFIC IN BOTH FLIES AND HUMANS JOURNAL OF NEUROSCIENCE Kim, Y. J., Baker, B. S. 1993; 13 (3): 1045-1056

    Abstract

    The rbp9 gene of Drosophila melanogaster has been molecularly characterized and shown to be expressed solely in the CNS, where it encodes proteins with three RNA recognition motifs (RRMs). Sequencing of genomic and cDNA clones of rbp9 revealed a complex gene with three alternative promoters as well as alternative patterns of splicing. The deduced amino acid sequence of the RBP9 proteins is highly similar to those of three other nervous system-specific genes, human HuC and HuD and Drosophila elav, which also encode proteins with three RRMs. Developmental Northern analysis revealed that rbp9 is expressed from the late third instar larva through adult stages. The RBP9 protein was detected specifically in nuclei of the nervous system after morphogenesis of the adult CNS in the mid-pupal stage. Thus, the RBP9 protein does not appear until substantially later than rbp9 transcripts are detected. The adult nervous system nuclear-limited expression pattern, the presence of RRMs, and the high similarity to a group of nervous system-specific proteins in flies and humans suggest that rbp9 belongs to a nervous system-specific RRM protein gene subfamily that may participate in the processing of RNAs involved in the development of the CNS.

    View details for Web of Science ID A1993KP71100015

    View details for PubMedID 7680064

  • REGULATION OF THE SEX-SPECIFIC BINDING OF THE MALELESS DOSAGE COMPENSATION PROTEIN TO THE MALE X-CHROMOSOME IN DROSOPHILA CELL Gorman, M., Kuroda, M. I., Baker, B. S. 1993; 72 (1): 39-49

    Abstract

    In Drosophila, the single male X chromosome is transcribed at twice the rate of a single female X chromosome. This hypertranscription requires the functions of at least four autosomal male-specific lethal genes (msls) and is under the control of the Sex-lethal (Sxl) gene. One of the msls, the maleless (mle) gene, encodes a protein that is associated with the male X chromosome. To investigate how dosage compensation is regulated, we have determined whether Sxl and the other msls are required for mle X chromosome binding. We have found that in females, Sxl functions to prevent mle from binding to the two X chromosomes. Additionally, we have found that mle X chromosome binding requires wild-type msl1, msl2, and msl3 functions. These data support a model whereby the activity of the mle protein is regulated through its association with one or more of the other msl proteins.

    View details for Web of Science ID A1993KG95500008

    View details for PubMedID 8422681

  • ISOLATION OF RRM-TYPE RNA-BINDING PROTEIN GENES AND THE ANALYSIS OF THEIR RELATEDNESS BY USING A NUMERICAL APPROACH MOLECULAR AND CELLULAR BIOLOGY Kim, Y. J., Baker, B. S. 1993; 13 (1): 174-183

    Abstract

    Proteins with RNA recognition motifs (RRMs) have important roles in a great many aspects of RNA metabolism. However, this family has yet to be systematically studied in any single organism. In order to investigate the size of the RRM gene family in Drosophila melanogaster and to clone members of this family, we used a polymerase chain reaction (PCR) with highly degenerate oligonucleotides to amplify DNA fragments between the RNP-1 and RNP-2 consensus sequences of the RRM proteins. Cloning and sequencing of 124 PCR products revealed 12 different RRM sequences (RRM1 to RRM12). When PCR products were used as probes in genomic Southern and Northern (RNA) analyses, 16 restriction fragments and 25 transcripts, respectively, were detected. Since the combinations of nucleotide sequences represented in the PCR primers correspond to only 4% of the RRM sequences inferred to be possible from known RRM sequences, we estimate the size of the RRM gene family in the order of three hundred genes in flies. In order to gain insight into the possible functions of the genes encoding the RRMs, we analyzed the sequence similarities between the 12 RRMs and 62 RRM sequences of known proteins. This analysis showed that the RRMs of functionally related proteins have similar sequences and are clustered together in the RRM gene tree. On the basis of this observation, the RRMs can be divided into three groups: a heterogeneous nuclear ribonucleoprotein type, a splicing regulator type, and a development-specific factor type. This result suggests that we have isolated good candidates for both housekeeping and developmentally important genes involved in RNA metabolism.

    View details for Web of Science ID A1993KD78500020

    View details for PubMedID 8417324

  • THE DROSOPHILA RNA-BINDING PROTEIN RBP1 IS LOCALIZED TO TRANSCRIPTIONALLY ACTIVE-SITES OF CHROMOSOMES AND SHOWS A FUNCTIONAL SIMILARITY TO HUMAN SPLICING FACTOR ASF/SF2 GENES & DEVELOPMENT Kim, Y. J., Zuo, P., Manley, J. L., Baker, B. S. 1992; 6 (12B): 2569-2579

    Abstract

    An RNA-binding protein gene (rbp1) from Drosophila melanogaster, encoding an RNA recognition motif and an Arg-Ser rich (RS) domain, has been characterized. The predicted amino acid sequence of rbp1 is similar to those of the human splicing factor ASF/SF2, the Drosophila nuclear phosphoprotein SRp55, and the Drosophila puff-associated protein B52. Northern and immunohistochemical analyses showed that rbp1 is expressed at all stages in all tissues and that the RBP1 protein is localized to the nucleus. Consistent with a role in mRNA metabolism, indirect immunofluorescence reveals that the RBP1 protein colocalizes with RNA polymerase II on larval salivary gland polytene chromosomes. RBP1 protein made in Escherichia coli was tested for splicing activity using human cell extracts in which ASF has been shown previously both to activate splicing and to affect the choice of splice sites in alternatively spliced pre-mRNAs. In these assays, RBP1 protein, like ASF, is capable of both activating splicing and switching splice site selection. However, in each case, clear differences in the behavior of the two proteins were detected, suggesting that they have related but not identical functions. The general nuclear expression pattern, colocalization on chromosomes with RNA polymerase II, the similarity to ASF/SF2, SRp55, and B52, along with the effect on alternative splicing shown in vitro, suggest that rbp1 is involved in the processing of precursor mRNAs.

    View details for Web of Science ID A1992KF41000012

    View details for PubMedID 1340470

  • AUTOREGULATION AND MULTIFUNCTIONALITY AMONG TRANS-ACTING FACTORS THAT REGULATE ALTERNATIVE PRE-MESSENGER-RNA PROCESSING JOURNAL OF BIOLOGICAL CHEMISTRY Mattox, W., Ryner, L., Baker, B. S. 1992; 267 (27): 19023-19026

    View details for Web of Science ID A1992JP59300001

    View details for PubMedID 1527029

  • REGULATION OF DOUBLESEX PRE-MESSENGER-RNA PROCESSING OCCURS BY 3'-SPLICE SITE ACTIVATION GENES & DEVELOPMENT Ryner, L. C., Baker, B. S. 1991; 5 (11): 2071-2085

    Abstract

    Sex-specific alternative processing of the doublesex (dsx) pre-mRNA controls somatic sexual differentiation in Drosophila melanogaster. Processing in the female-specific pattern results from the utilization of an upstream 3'-terminal exon and requires the activities of both the transformer (tra) and transformer-2 (tra-2) genes. Use of the more downstream male-specific terminal exons does not require the activities of these genes and is thus considered the default dsx-processing pattern. Here, we used transient expression of dsx pre-mRNAs in the presence or absence of tra and tra-2 gene products in Drosophila tissue culture cells to investigate the molecular mechanism controlling this alternative RNA-processing decision. These studies reveal that female-specific processing of dsx pre-mRNA is controlled by tra and tra-2 through the positive regulation of female-specific alternative 3'-terminal exon use. Delineation of cis-acting sequences necessary for regulation shows that a 540-nucleotide region from within the female exon is both necessary and sufficient for regulation. In addition, utilization of the female-specific 3'-splice site (3'SS) is regulated independently of female-specific polyadenylation. Regulated polyadenylation was obtained only in the presence of splicing, suggesting that activation of female-specific exon use occurs by 3'SS activation.

    View details for Web of Science ID A1991GP03800013

    View details for PubMedID 1936994

  • THE MALELESS PROTEIN ASSOCIATES WITH THE X-CHROMOSOME TO REGULATE DOSAGE COMPENSATION IN DROSOPHILA CELL Kuroda, M. I., Kernan, M. J., Kreber, R., Ganetzky, B., Baker, B. S. 1991; 66 (5): 935-947

    Abstract

    The maleless (mle) gene is one of four known regulatory loci required for increased transcription (dosage compensation) of X-linked genes in D. melanogaster males. A predicted mle protein (MLE) contains seven short segments that define a superfamily of known and putative RNA and DNA helicases. MLE, while present in the nuclei of both male and female cells, differs in its association with polytene X chromosomes in the two sexes. MLE is associated with hundreds of discrete sites along the length of the X chromosome in males and not in females. The predominant localization of MLE to the X chromosome in males makes it a strong candidate to be a direct regulator of dosage compensation.

    View details for Web of Science ID A1991GE46000012

    View details for PubMedID 1653648

  • AUTOREGULATION OF THE SPLICING OF TRANSCRIPTS FROM THE TRANSFORMER-2 GENE OF DROSOPHILA GENES & DEVELOPMENT Mattox, W., Baker, B. S. 1991; 5 (5): 786-796

    Abstract

    The Drosophila transformer-2 gene uses alternative promoters and splicing patterns to generate four different mRNAs that together encode three putative RNA-binding polypeptides. The transformer-2 products expressed in somatic tissues function to regulate the RNA splicing of the sex determination gene doublesex, whereas products expressed in the male germ line play an unknown, but essential, role in spermatogenesis. Two alternatively spliced transformer-2 transcripts, each encoding a different putative RNA-binding protein, are found only in the male germ line. These male germ line-specific mRNAs differ from each other by the presence or absence of a single intron called M1. We show that M1-containing transcripts make up a majority of transformer-2 germ-line transcripts in wild-type males but fail to accumulate in males homozygous for transformer-2 null mutations. Germ-line transformation experiments using a variety of reporter gene constructs demonstrate that specific polypeptide products of the transformer-2 gene itself normally repress M1 splicing in the male germ line. Thus, in addition to its role in the sex-specific control of doublesex RNA splicing in somatic tissues, the transformer-2 gene also regulates the splicing of its own transcripts in the male germ line. We propose that this autoregulatory function may serve in negative feedback control of transformer-2 activity during spermatogenesis. The finding that transformer-2 controls multiple splicing decisions suggests that a variety of different alternative splicing choices could be regulated by a relatively limited number of trans-acting factors.

    View details for Web of Science ID A1991FK81300008

    View details for PubMedID 2026327

  • ALTERNATIVE SPLICING OF THE SEX DETERMINATION GENE TRANSFORMER-2 IS SEX-SPECIFIC IN THE GERM LINE BUT NOT IN THE SOMA GENES & DEVELOPMENT Mattox, W., Palmer, M. J., Baker, B. S. 1990; 4 (5): 789-805

    Abstract

    The transformer-2 (tra-2) gene of Drosophila melanogaster plays essential roles in both sexual differentiation in the female soma and spermatogenesis in the male germ line. In the female soma, tra-2 is known to act with other genes in the sex determination regulatory cascade to control the sex-specific alternative splicing of transcripts from the doublesex gene. Here, we determine whether or not any sex-specific tra-2 products are expressed that may account for either of these sex-specific activities. Sequence analysis of the tra-2 gene and 10 tra-2 cDNA clones coupled with nuclease protection analysis reveals a variety of alternatively spliced tra-2 mRNAs that each encode one of four distinct but overlapping polypeptides. Three of the encoded polypeptides contain both a ribonucleoprotein consensus sequence and arginine/serine-rich regions, suggesting a direct role for these products in RNA splicing. We show that although two transcripts are expressed male specifically in the germ line, the tra-2 transcripts expressed in the soma are not sex-specific. The translation of products from a tra-2-lacZ fusion gene in both sexes suggests that the female-specific functioning of tra-2 in somatic tissues is not attributable to a translational mechanism. We suggest that tra-2 activity in somatic tissues is regulated through a post-translational sex-specific interaction with the product of the tra gene rather than through the expression of a female-specific tra-2 polypeptide.

    View details for Web of Science ID A1990DE56300009

    View details for PubMedID 2116360

  • REGULATION OF SEX-SPECIFIC RNA SPLICING AT THE DROSOPHILA DOUBLESEX GENE - CIS-ACTING MUTATIONS IN EXON SEQUENCES ALTER SEX-SPECIFIC RNA SPLICING PATTERNS GENES & DEVELOPMENT Nagoshi, R. N., Baker, B. S. 1990; 4 (1): 89-97

    Abstract

    Sex-specific alternative RNA splicing of the doublesex (dsx) pre-mRNA results in sex-specific polypeptides that regulate both male and female somatic sexual differentiation in Drosophila melanogaster. We have molecularly characterized a class of dsx mutations that act in cis to disrupt the regulation of dsx RNA processing, causing the dsx pre-mRNA to be spliced in the male-specific pattern regardless of the chromosomal sex of the fly. These dsx mutations are associated with rearrangements in the female-specific exon just 3' to the female-specific splice acceptor. The mutations do not affect the female-specific splice sites or intron that are identical to wild-type sequences. These results indicate that sequences in the female-specific exon are important for the regulation of sex-specific RNA splicing, perhaps by acting as sites of interaction with trans-acting regulators. Furthermore, the data suggest that female-specific regulation of dsx RNA processing occurs by promoting the usage of the female splice acceptor site, rather than by repressing the usage of the alternative male-specific splice acceptor.

    View details for Web of Science ID A1990CL68900009

    View details for PubMedID 2155161

  • SEX IN FLIES - THE SPLICE OF LIFE NATURE Baker, B. S. 1989; 340 (6234): 521-524

    Abstract

    The discovery that the primary transcripts of many genes are processed to produce more than one kind of messenger RNA focuses attention on the control of RNA processing as a developmental regulatory mechanism. In the fruit-fly Drosophila melanogaster, differential splicing of a hierarchy of regulatory genes determines sex, and thus the molecular biology of sex determination in the fruit-fly may lead to insights into the mechanisms by which alternative splicing is regulated.

    View details for Web of Science ID A1989AL22700047

    View details for PubMedID 2505080

  • DROSOPHILA DOUBLESEX GENE CONTROLS SOMATIC SEXUAL-DIFFERENTIATION BY PRODUCING ALTERNATIVELY SPLICED MESSENGER-RNAS ENCODING RELATED SEX-SPECIFIC POLYPEPTIDES CELL Burtis, K. C., Baker, B. S. 1989; 56 (6): 997-1010

    Abstract

    The doublesex (dsx) gene regulates somatic sexual differentiation in both sexes in D. melanogaster. Two functional products are encoded by dsx: one product is expressed in females and represses male differentiation, and the other is expressed in males and represses female differentiation. We have determined that the dsx gene is transcribed to produce a common primary transcript that is alternatively spliced and polyadenylated to yield male- and female-specific mRNAs. These sex-specific mRNAs share a common 5' end and three common exons, but possess alternative sex-specific 3' exons, thus encoding polypeptides with a common amino-terminal sequence but sex-specific carboxyl termini. Genetic and molecular data suggest that sequences including and adjacent to the female-specific splice acceptor site play an important role in the regulation of dsx expression by the transformer and transformer-2 loci.

    View details for Web of Science ID A1989T944600014

    View details for PubMedID 2493994

  • THE SEX DETERMINATION LOCUS TRANSFORMER-2 OF DROSOPHILA ENCODES A POLYPEPTIDE WITH SIMILARITY TO RNA-BINDING PROTEINS CELL Goralski, T. J., Edstrom, J. E., Baker, B. S. 1989; 56 (6): 1011-1018

    Abstract

    The D. melanogaster transformer-2 (tra-2) gene regulates somatic sexual differentiation in females and is necessary for spermatogenesis in males. Wild-type tra-2 function is required for the female-specific splicing of the pre-mRNA of the next known gene (doublesex) downstream of tra-2 in the sex determination regulatory hierarchy. The tra-2 gene was cloned, and P element-mediated transformation was used to demonstrate that a 3.9 kb genomic fragment contains all sequences necessary for tra-2 function. A 1.7 kb transcript was shown to be the product of the tra-2 locus based on its reduced level in flies containing a tra-2 mutant allele. The sequence of a cDNA corresponding to this transcript indicates that it encodes a polypeptide with strong similarity to a family of RNA binding proteins that includes proteins found associated with hnRNPs and snRNPs, suggesting that the tra-2 product may directly regulate the processing of the double-sex pre-mRNA in females.

    View details for Web of Science ID A1989T944600015

    View details for PubMedID 2493992

  • THE CONTROL OF ALTERNATIVE SPLICING AT GENES REGULATING SEXUAL-DIFFERENTIATION IN DROSOPHILA-MELANOGASTER CELL Nagoshi, R. N., McKeown, M., Burtis, K. C., Belote, J. M., Baker, B. S. 1988; 53 (2): 229-236

    Abstract

    The transformer (tra) and doublesex (dsx) genes produce sex-specific transcripts that are generated by differential RNA processing. We have examined the effects of mutants in other regulatory genes controlling sexual differentiation on the patterns of processing of the tra and dsx RNA transcripts. Our results demonstrate that the genes suggested by genetic studies to act upstream of tra or dsx in the sex determination hierarchy regulate these two loci at the level of RNA processing. Our data suggest that the order of interaction of the factors controlling sex is X:A greater than Sxl greater than tra greater than tra-2 greater than dsx greater than or equal to ix greater than terminal differentiation. While these results cannot preclude regulatory interactions at other levels, the regulation of RNA splicing revealed by these experiments is sufficient to account for all of the known functional interactions between the regulatory genes in this hierarchy.

    View details for Web of Science ID A1988N126600008

    View details for PubMedID 3129196

Conference Proceedings


  • MOLECULAR GENETIC-ASPECTS OF SEX DETERMINATION IN DROSOPHILA-MELANOGASTER Baker, B. S., Burtis, K., Goralski, T., Mattox, W., Nagoshi, R. NATL RESEARCH COUNCIL CANADA. 1989: 638-645

    Abstract

    The molecular analyses of three of the regulatory genes (transformer (tra), doublesex (dsx), and transformer-2 (tra-2)) controlling sexual differentiation in Drosophila have demonstrated that the control of RNA processing has a major role in regulating somatic sexual differentiation. The activities of both the tra and dsx genes are controlled at the level of RNA processing. In the case of tra the use of different splice acceptor sites results in a functional transcript being produced only in females, whereas at dsx the use of different splice acceptor sites in the two sexes results in the production of transcripts that encode different proteins in males and females. The tra-2 gene has been shown to be necessary for the processing of the dsx pre-mRNA in females and the conceptual translation of a tra-2 cDNA shows that it encodes a protein with similarity to a family of RNA-binding proteins which includes known splicesome components. We previously suggested that the pattern of sexual differentiation and dosage compensation characteristic of a male was a default regulatory state. The findings reviewed here provide a molecular basis for this default expression in males as well as an insight into how females differ from males in control of the expression of these genes. For both the tra and dsx genes the molecular basis of their male (default) state of expression appears to be the processing of their transcripts by the housekeeping RNA splicing machinery.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1989CL22100022

    View details for PubMedID 2517260

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