Maria Barna

Journal Articles

• Specialized filopodia direct long-range transport of SHH during vertebrate tissue patterning. Nature Sanders, T. A., Llagostera, E., Barna, M. 2013; 497 (7451): 628-632

  Abstract

  The ability of signalling proteins to traverse tissues containing tightly packed cells is of fundamental importance for cell specification and tissue development; however, how this is achieved at a cellular level remains poorly understood. For more than a century, the vertebrate limb bud has served as a model for studying cell signalling during embryonic development. Here we optimize single-cell real-time imaging to delineate the cellular mechanisms for how signalling proteins, such as sonic hedgehog (SHH), that possess membrane-bound covalent lipid modifications traverse long distances within the vertebrate limb bud in vivo. By directly imaging SHH ligand production under native regulatory control in chick (Gallus gallus) embryos, our findings show that SHH is unexpectedly produced in the form of a particle that remains associated with the cell via long cytoplasmic extensions that span several cell diameters. We show that these cellular extensions are a specialized class of actin-based filopodia with novel cytoskeletal features that have not been previously described. Notably, particles containing SHH travel along these extensions with a net anterograde movement within the field of SHH cell signalling. We further show that in SHH-responding cells, specific subsets of SHH co-receptors, including cell adhesion molecule downregulated by oncogenes (CDO) and brother of CDO (BOC), actively distribute and co-localize in specific micro-domains within filopodial extensions, far from the cell body. Stabilized interactions are formed between filopodia containing SHH ligand and those containing co-receptors over a long range. These results suggest that contact-mediated release propagated by specialized filopodia contributes to the delivery of SHH at a distance. Together, these studies identify an important mode of communication between cells that considerably extends our understanding of ligand movement and reception during vertebrate tissue patterning.

  View details for DOI 10.1038/nature12157

  View details for PubMedID 23624372

• Ribosomes take control PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Barna, M. 2013; 110 (1): 9-10

  View details for DOI 10.1073/pnas.1218764110

  View details for Web of Science ID 000313630300020

  View details for PubMedID 23243144

• Specialized ribosomes: a new frontier in gene regulation and organismal biology NATURE REVIEWS MOLECULAR CELL BIOLOGY Xue, S., Barna, M. 2012; 13 (6): 355-369

  Abstract

  Historically, the ribosome has been viewed as a complex ribozyme with constitutive rather than intrinsic regulatory capacity in mRNA translation. However, emerging studies reveal that ribosome activity may be highly regulated. Heterogeneity in ribosome composition resulting from differential expression and post-translational modifications of ribosomal proteins, ribosomal RNA (rRNA) diversity and the activity of ribosome-associated factors may generate 'specialized ribosomes' that have a substantial impact on how the genomic template is translated into functional proteins. Moreover, constitutive components of the ribosome may also exert more specialized activities by virtue of their interactions with specific mRNA regulatory elements such as internal ribosome entry sites (IRESs) or upstream open reading frames (uORFs). Here we discuss the hypothesis that intrinsic regulation by the ribosome acts to selectively translate subsets of mRNAs harbouring unique cis-regulatory elements, thereby introducing an additional level of regulation in gene expression and the life of an organism.

  View details for DOI 10.1038/nrm3359

  View details for Web of Science ID 000304354100011

  View details for PubMedID 22617470

• Ribosome-Mediated Specificity in Hox mRNA Translation and Vertebrate Tissue Patterning CELL Kondrashov, N., Pusic, A., Stumpf, C. R., Shimizu, K., Hsieh, A. C., Xue, S., Ishijima, J., Shiroishi, T., Barna, M. 2011; 145 (3): 383-397

  Abstract

  Historically, the ribosome has been viewed as a complex ribozyme with constitutive rather than regulatory capacity in mRNA translation. Here we identify mutations of the Ribosomal Protein L38 (Rpl38) gene in mice exhibiting surprising tissue-specific patterning defects, including pronounced homeotic transformations of the axial skeleton. In Rpl38 mutant embryos, global protein synthesis is unchanged; however the translation of a select subset of Homeobox mRNAs is perturbed. Our data reveal that RPL38 facilitates 80S complex formation on these mRNAs as a regulatory component of the ribosome to confer transcript-specific translational control. We further show that Rpl38 expression is markedly enriched in regions of the embryo where loss-of-function phenotypes occur. Unexpectedly, a ribosomal protein (RP) expression screen reveals dynamic regulation of individual RPs within the vertebrate embryo. Collectively, these findings suggest that RP activity may be highly regulated to impart a new layer of specificity in the control of gene expression and mammalian development.

  View details for DOI 10.1016/j.cell.2011.03.028

  View details for Web of Science ID 000290022900008

  View details for PubMedID 21529712

• Suppression of Myc oncogenic activity by ribosomal protein haploinsufficiency NATURE Barna, M., Pusic, A., Zollo, O., Costa, M., Kondrashov, N., Rego, E., Rao, P. H., Ruggero, D. 2008; 456 (7224): 971-U79

  Abstract

  The Myc oncogene regulates the expression of several components of the protein synthetic machinery, including ribosomal proteins, initiation factors of translation, RNA polymerase III and ribosomal DNA. Whether and how increasing the cellular protein synthesis capacity affects the multistep process leading to cancer remains to be addressed. Here we use ribosomal protein heterozygote mice as a genetic tool to restore increased protein synthesis in Emu-Myc/+ transgenic mice to normal levels, and show that the oncogenic potential of Myc in this context is suppressed. Our findings demonstrate that the ability of Myc to increase protein synthesis directly augments cell size and is sufficient to accelerate cell cycle progression independently of known cell cycle targets transcriptionally regulated by Myc. In addition, when protein synthesis is restored to normal levels, Myc-overexpressing precancerous cells are more efficiently eliminated by programmed cell death. Our findings reveal a new mechanism that links increases in general protein synthesis rates downstream of an oncogenic signal to a specific molecular impairment in the modality of translation initiation used to regulate the expression of selective messenger RNAs. We show that an aberrant increase in cap-dependent translation downstream of Myc hyperactivation specifically impairs the translational switch to internal ribosomal entry site (IRES)-dependent translation that is required for accurate mitotic progression. Failure of this translational switch results in reduced mitotic-specific expression of the endogenous IRES-dependent form of Cdk11 (also known as Cdc2l and PITSLRE), which leads to cytokinesis defects and is associated with increased centrosome numbers and genome instability in Emu-Myc/+ mice. When accurate translational control is re-established in Emu-Myc/+ mice, genome instability is suppressed. Our findings demonstrate how perturbations in translational control provide a highly specific outcome for gene expression, genome stability and cancer initiation that have important implications for understanding the molecular mechanism of cancer formation at the post-genomic level.

  View details for DOI 10.1038/nature07449

  View details for Web of Science ID 000261768300050

  View details for PubMedID 19011615

• Visualization of cartilage formation: Insight into cellular properties of skeletal progenitors and chondrodysplasia syndromes DEVELOPMENTAL CELL Barna, M., Niswander, L. 2007; 12 (6): 931-941

  Abstract

  The cellular events underlying skeletal morphogenesis and the formation of cartilage templates are largely unknown. We generated an imaging system to dynamically visualize limb mesenchymal cells undergoing successive phases in cartilage formation and to delineate the cellular function of key regulators of chondrogenesis found mutated in chondrodysplasia syndromes. We uncovered an unsuspected role for Sox9 in control of cell morphology, independent from its major downstream target ColIIa, critically required for the mesenchyme-to-chondrocyte transition. In contrast, Bmp signaling regulates a cellular program we term "compaction" in which mesenchymal cells acquire a cohesive cell behavior required to delineate the boundaries and size of cartilage elements. Moreover, we visualized labeled progenitor cells from different regions of the limb bud and identified unique cellular properties that may direct their contribution toward specific skeletal elements such as the humerus or digits. These findings shed light on the cellular basis for chondrodysplasia syndromes and formation of the vertebrate skeleton.

  View details for DOI 10.1016/j.devcel.2007.04.016

  View details for Web of Science ID 000247119700013

  View details for PubMedID 17543865

• Gli3 and Plzf cooperate in proximal limb patterning at early stages of limb development NATURE Barna, M., Pandolfi, P. P., Niswander, L. 2005; 436 (7048): 277-281

  Abstract

  The vertebrate limb initially develops as a bud of mesenchymal cells that subsequently aggregate in a proximal to distal (P-D) sequence to give rise to cartilage condensations that prefigure all limb skeletal components. Of the three cardinal limb axes, the mechanisms that lead to establishment and patterning of skeletal elements along the P-D axis are the least understood. Here we identify a genetic interaction between Gli3 (GLI-Kruppel family member 3) and Plzf (promyelocytic leukaemia zinc finger, also known as Zbtb16 and Zfp145), which is required specifically at very early stages of limb development for all proximal cartilage condensations in the hindlimb (femur, tibia, fibula). Notably, distal condensations comprising the foot are relatively unperturbed in Gli3(-/-);Plzf(-/-) mouse embryos. We demonstrate that the cooperative activity of Gli3 and Plzf establishes the correct temporal and spatial distribution of chondrocyte progenitors in the proximal limb-bud independently of known P-D patterning markers and overall limb-bud size. Moreover, the limb defects in Gli3(-/-);Plzf(-/-) embryos correlate with the transient death of a specific subset of proximal mesenchymal cells that express bone morphogenetic protein receptor, type 1B (Bmpr1b) at the onset of limb development. These findings suggest that the development of proximal and distal skeletal elements is distinctly regulated early during limb-bud formation. The initial division of the vertebrate limb into two distinct molecular domains is consistent with fossil evidence indicating that the upper and lower extremities of the limb have different evolutionary origins.

  View details for DOI 10.1038/nature03801

  View details for Web of Science ID 000230459500045

  View details for PubMedID 16015334

• Essential role of Plzf in maintenance of spermatogonial stem cells NATURE GENETICS Costoya, J. A., Hobbs, R. M., Barna, M., Cattoretti, G., Manova, K., Sukhwani, M., Orwig, K. E., Wolgemuth, D. J., Pandolfi, P. P. 2004; 36 (6): 653-659

  Abstract

  Little is known of the molecular mechanisms whereby spermatogonia, mitotic germ cells of the testis, self-renew and differentiate into sperm. Here we show that Zfp145, encoding the transcriptional repressor Plzf, has a crucial role in spermatogenesis. Zfp145 expression was restricted to gonocytes and undifferentiated spermatogonia and was absent in tubules of W/W(v) mutants that lack these cells. Mice lacking Zfp145 underwent a progressive loss of spermatogonia with age, associated with increases in apoptosis and subsequent loss of tubule structure but without overt differentiation defects or loss of the supporting Sertoli cells. Spermatogonial transplantation experiments revealed a depletion of spermatogonial stem cells in the adult. Microarray analysis of isolated spermatogonia from Zfp145-null mice before testis degeneration showed alterations in the expression profile of genes associated with spermatogenesis. These results identify Plzf as a spermatogonia-specific transcription factor in the testis that is required to regulate self-renewal and maintenance of the stem cell pool.

  View details for DOI 10.1038/ng1367

  View details for Web of Science ID 000221763700026

  View details for PubMedID 15156143

• Plzf mediates transcriptional repression of HoxD gene expression through chromatin remodeling DEVELOPMENTAL CELL Barna, M., Merghoub, T., Costoya, J. A., Ruggero, D., Branford, M., Bergia, A., Samori, B., Pandolfi, P. P. 2002; 3 (4): 499-510

  Abstract

  The molecular mechanisms that regulate coordinated and colinear activation of Hox gene expression in space and time remain poorly understood. Here we demonstrate that Plzf regulates the spatial expression of the AbdB HoxD gene complex by binding to regulatory elements required for restricted Hox gene expression and can recruit histone deacetylases to these sites. We show by scanning forced microscopy that Plzf, via homodimerization, can form DNA loops and bridge distant Plzf binding sites located within HoxD gene regulatory elements. Furthermore, we demonstrate that Plzf physically interacts with Polycomb proteins on DNA. We propose a model by which the balance between activating morphogenic signals and transcriptional repressors such as Plzf establishes proper Hox gene expression boundaries in the limb bud.

  View details for Web of Science ID 000178629300008

  View details for PubMedID 12408802

• Plzf regulates limb and axial skeletal patterning NATURE GENETICS Barna, M., Hawe, N., Niswander, L., Pandolfi, P. P. 2000; 25 (2): 166-172

  Abstract

  The promyelocytic leukaemia zinc finger (Plzf) protein (encoded by the gene Zfp145) belongs to the POZ/zinc-finger family of transcription factors. Here we generate Zfp145-/- mice and show that Plzf is essential for patterning of the limb and axial skeleton. Plzf inactivation results in patterning defects affecting all skeletal structures of the limb, including homeotic transformations of anterior skeletal elements into posterior structures. We demonstrate that Plzf acts as a growth-inhibitory and pro-apoptotic factor in the limb bud. The expression of members of the abdominal b (Abdb) Hox gene complex, as well as genes encoding bone morphogenetic proteins (Bmps), is altered in the developing limb of Zfp145-/- mice. Plzf regulates the expression of these genes in the absence of aberrant polarizing activity and independently of known patterning genes. Zfp145-/- mice also exhibit anterior-directed homeotic transformation throughout the axial skeleton with associated alterations in Hox gene expression. Plzf is therefore a mediator of anterior-to-posterior (AP) patterning in both the axial and appendicular skeleton and acts as a regulator of Hox gene expression.

  View details for Web of Science ID 000087459200014

  View details for PubMedID 10835630

• Interleukin-12 promotes recovery from viral encephalitis VIRAL IMMUNOLOGY Komatsu, T., Barna, M., Reiss, C. S. 1997; 10 (1): 35-47

  Abstract

  Infusion of interleukin-12 (IL-12) enhances recovery from lethal experimental vesicular stomatitis virus (VSV) infection of the central nervous system (CNS). Interleukin-12 treatment resulted in: 1) increased survival frequency; 2) faster recovery from weight loss; 3) substantially decreased VSV titers in brain homogenates and diminished immunohistochemical detection of VSV antigens in tissue sections; 4) earlier and increased CNS expression of types 1, 2, and 3 nitric oxide synthase (NOS) and both major histocompatibility complex (MHC) class I and class II antigens; 5) earlier and increased blood and CNS levels of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). These results suggest that IL-12 enhances recovery from VSV infection of the CNS.

  View details for Web of Science ID A1997YA74900005

  View details for PubMedID 9095530

• Activation of type III nitric oxide synthase in astrocytes following a neurotropic viral infection VIROLOGY Barna, M., Komatsu, T., Reiss, C. S. 1996; 223 (2): 331-343

  Abstract

  Type III nitric oxide synthase (type III NOS), also known as endothelial cell nitric oxide synthase (eNOS or ecNOS or NOS-3), is a constitutively expressed, calcium- and calmodulin-dependent, isoform of NOS. Its expression has been localized to endothelial cells and a subset of neurons in the brain. We report here that resident astrocytes of the central nervous system (CNS) of mice express type III NOS. Following an experimental neurotropic viral infection, the expression of type III NOS on reactive astrocytes increases substantially, predominantly in virally infected regions of the brain. This upregulation of type III NOS expression is also evident following cytokine treatment in vitro. The intraperitoneal (i.p.) administration of IL-12, a potent activator of IFN-gamma and TNF-alpha production, results in a substantial increase in type III NOS immunoreactivity in astrocytes. Cytokine-mediated activation of type III NOS is observed in vitro following exposure of a C6 glioma cells, which constitutively express type III NOS, to IL-12, IFN-gamma, and TNF-alpha treatment. We conclude that astrocytes of the murine CNS express type III NOS, which may be positively regulated by a number of cytokines following viral infection. Type III NOS expression by astrocytes represents a novel source of nitric oxide in the brain. It may be important in regulating perfusion and maintaining the blood-brain barrier. Given the intimate association of astrocytes with endothelial cells and neurons, increased activity of type III NOS following viral infection may be beneficial in inhibition of viral infection in neighboring cells.

  View details for Web of Science ID A1996VJ81000007

  View details for PubMedID 8806568

• Sex differences in susceptibility to viral infection of the central nervous system JOURNAL OF NEUROIMMUNOLOGY Barna, M., Komatsu, T., Bi, Z. B., Reiss, C. S. 1996; 67 (1): 31-39

  Abstract

  We have characterized striking differences in recovery of male and female BALB/c and BALB/c-H-2dm2 (dm2) mice from an experimental neurotropic viral infection of the central nervous system (CNS). Following intranasal inoculation of vesicular stomatitis virus (VSV), assays of tissue homogenates from female mice produced lower viral titers. There was also a significant reduction in the spread of virus from the rostral to caudal end of the brain in female mice. Enhanced recovery by female mice of both strains in response to this viral insult correlates with increased levels of Nitric Oxide Synthase (NOS) types I, II, and III expression, an increased prevalence of reactive astrocytes, earlier and enhanced levels of expression of Major Histocompatibility Complex (MHC) class II molecules on astrocytes, endothelial and microglial cells, and increased T cell infiltration in the female BALB/c mouse. Taken together, these findings document sexual dimorphism in CNS immunity, and may provide an understanding of some of the mechanisms underlying many sex-biased diseases.

  View details for Web of Science ID A1996VA91900005

  View details for PubMedID 8707928

• Interleukin-12: Promotes enhanced recovery from viral infection of neurons in the central nervous system INERLEUKIN 12: CELLULAR AND MOLECULAR IMMUNOLOGY OF AN IMPORTANT REGULATORY CYTOKINE Reiss, C. S., Komatsu, T., Barna, M., Bi, Z. B. 1996; 795: 257-265

  View details for Web of Science ID 000070968300027

  View details for PubMedID 8958937

• Host immune response to vesicular stomatitis virus infection of the central nervous system in C57BL/6 mice VIRAL IMMUNOLOGY CHRISTIAN, A. Y., Barna, M., Bi, Z. B., Reiss, C. S. 1996; 9 (3): 195-205

  Abstract

  In this report, the kinetics of cellular inflammatory changes in the brain of vesicular stomatitis virus (VSV)-infected C57BL/6 (B6) mice was determined. The behavior and survival rate of infected B6 were carefully monitored each day. Infectious viral titers and VSV antigen distribution were determined at several time points during the course of infection. Strong activation of both astrocytes and microglia was observed after VSV infection. Induction of type II nitric oxide synthase (iNOS) was detected in activated microglia in the olfactory bulb (OB) starting at day 4 postinfection. Induced expression of major histocompatibility complex (MHC) molecules and rapid infiltration of both T cells and natural killer (NK) cells were detected in the VSV-infected CNS. Collectively, these data indicate that the response to CNS infection in B6 mice, which is often primarily Th1 in characteristics, is comparable to BALB/c mice, a strain that often shows a Th2-dominated immune response.

  View details for Web of Science ID A1996VK05900007

  View details for PubMedID 8890478

• IL-12 PROMOTES ENHANCED RECOVERY FROM VESICULAR STOMATITIS-VIRUS INFECTION OF THE CENTRAL-NERVOUS-SYSTEM JOURNAL OF IMMUNOLOGY Bi, Z. B., QUANDT, P., Komatsu, T., Barna, M., Reiss, C. S. 1995; 155 (12): 5684-5689

  Abstract

  To investigate the role of a cytokine in host defense against the vesicular stomatitis virus (VSV) infection of the central nervous system (CNS), IL-12 was injected i.p. into groups of 10 BALB/c mice on days -1, 0, 1, 2, and 3 postinfection. Four days postinfection, mice were examined. IL-12 strongly enhanced immunity to VSV infection in the CNS as demonstrated by 1) decreased VSV titers in brain homogenate of IL-12-injected mice compared with those of controls; 2) increased expression of inducible nitric oxide synthase in the CNS; 3) enhanced expression of both MHC class I and class II Ags in the CNS; 4) increased T cell infiltration in the CNS, especially in the olfactory bulb; and 5) diminished VSV-induced apoptosis in olfactory bulb. No detrimental effect was observed even with the 200 ng/mouse dose of IL-12. Protective effects of IL-12 were dose dependent. Collectively, these results demonstrate that exogenously added IL-12, even when injected peripherally, significantly enhances recovery from VSV infection of the CNS.

  View details for Web of Science ID A1995TJ63100030

  View details for PubMedID 7499854

• VESICULAR STOMATITIS-VIRUS INFECTION OF THE CENTRAL-NERVOUS-SYSTEM ACTIVATES BOTH INNATE AND ACQUIRED-IMMUNITY JOURNAL OF VIROLOGY Bi, Z. B., Barna, M., Komatsu, T., Reiss, C. S. 1995; 69 (10): 6466-6472

  Abstract

  Vesicular stomatitis virus (VSV) causes acute infection of the central nervous system (CNS) when intranasally applied. We have examined cellular inflammatory changes in the CNS following VSV infection. As early as 1 day postinfection (p.i.), astrocytes were activated in the olfactory bulb (OB). This was followed by activation of microglia, first observed in the OB at day 3 p.i. Expression of inducible nitric oxide synthase was observed in activated microglia in the OB at day 3 p.i., and increased inducible nitric oxide synthase expression coincided with decreased virus titers in tissue homogenates. Expression of major histocompatibility complex (MHC) class I molecules on astrocytes and microglial, endothelial, and ependymal cells was also rapidly induced and followed by induced expression of MHC class II molecules on astrocytes and microglial and endothelial cells. Consistent with the pattern of viral dissemination, MHC molecules were expressed temporally from the rostral-to-caudal direction. Infiltration of CD8+ cells was observed as early as 1 day p.i. in the OB. CD4+ cells were detected in the OB at day 4 p.i. Increasing T-cell infiltration coincided with decreased virus titers. In contrast, B-cell infiltration of the CNS was not detected until day 14 p.i., after the virus was cleared and mice were showing behavioral signs of recovery. Breakdown of the blood-brain barrier was detected beginning at day 6 p.i., was most severe at day 8 p.i., and was followed by full recovery. Collectively, these data show that both innate immunity (production of nitric oxide) and acquired immunity (expression of MHC molecules and T-cell infiltration) are activated following VSV infection in the CNS.

  View details for Web of Science ID A1995RU78400061

  View details for PubMedID 7545248