Academic Appointments


All Publications

  • SCML2 promotes heterochromatin organization in late spermatogenesis JOURNAL OF CELL SCIENCE Maezawa, S., Hasegawa, K., Alavattam, K. G., Funakoshi, M., Sato, T., Barski, A., Namekawa, S. H. 2018; 131 (17)


    Spermatogenesis involves the progressive reorganization of heterochromatin. However, the mechanisms that underlie the dynamic remodeling of heterochromatin remain unknown. Here, we identify SCML2, a germline-specific Polycomb protein, as a critical regulator of heterochromatin organization in spermatogenesis. We show that SCML2 accumulates on pericentromeric heterochromatin (PCH) in male germ cells, where it suppresses PRC1-mediated monoubiquitylation of histone H2A at Lysine 119 (H2AK119ub) and promotes deposition of PRC2-mediated H3K27me3 during meiosis. In postmeiotic spermatids, SCML2 is required for heterochromatin organization, and the loss of SCML2 leads to the formation of ectopic patches of facultative heterochromatin. Our data suggest that, in the absence of SCML2, the ectopic expression of somatic lamins drives this process. Furthermore, the centromere protein CENP-V is a specific marker of PCH in postmeiotic spermatids, and SCML2 is required for CENP-V localization on PCH. Given the essential functions of PRC1 and PRC2 for genome-wide gene expression in spermatogenesis, our data suggest that heterochromatin organization and spermatogenesis-specific gene expression are functionally linked. We propose that SCML2 coordinates the organization of heterochromatin and gene expression through the regulation of Polycomb complexes.

    View details for DOI 10.1242/jcs.217125

    View details for Web of Science ID 000444707000013

    View details for PubMedID 30097555

    View details for PubMedCentralID PMC6140322

  • Polycomb protein SCML2 facilitates H3K27me3 to establish bivalent domains in the male germline PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Maezawa, S., Hasegawa, K., Yukawa, M., Kubo, N., Sakashita, A., Alavattam, K. G., Sin, H., Kartashov, A. V., Sasaki, H., Barski, A., Namekawa, S. H. 2018; 115 (19): 4957?62


    Repressive H3K27me3 and active H3K4me2/3 together form bivalent chromatin domains, molecular hallmarks of developmental potential. In the male germline, these domains are thought to persist into sperm to establish totipotency in the next generation. However, it remains unknown how H3K27me3 is established on specific targets in the male germline. Here, we demonstrate that a germline-specific Polycomb protein, SCML2, binds to H3K4me2/3-rich hypomethylated promoters in undifferentiated spermatogonia to facilitate H3K27me3. Thus, SCML2 establishes bivalent domains in the male germline of mice. SCML2 regulates two major classes of bivalent domains: Class I domains are established on developmental regulator genes that are silent throughout spermatogenesis, while class II domains are established on somatic genes silenced during late spermatogenesis. We propose that SCML2-dependent H3K27me3 in the male germline prepares the expression of developmental regulator and somatic genes in embryonic development.

    View details for DOI 10.1073/pnas.1804512115

    View details for Web of Science ID 000431639100059

    View details for PubMedID 29686098

    View details for PubMedCentralID PMC5949012

  • Purification of GFR alpha 1+and GFR alpha 1-Spermatogonial Stem Cells Reveals a Niche-Dependent Mechanism for Fate Determination STEM CELL REPORTS Garbuzov, A., Pech, M. F., Hasegawa, K., Sukhwani, M., Zhang, R. J., Orwig, K. E., Artandi, S. E. 2018; 10 (2): 553?67


    Undifferentiated spermatogonia comprise a pool of stem cells and progenitor cells that show heterogeneous expression of markers, including the cell surface receptor GFR?1. Technical challenges in isolation of GFR?1+ versus GFR?1- undifferentiated spermatogonia have precluded the comparative molecular characterization of these subpopulations and their functional evaluation as stem cells. Here, we develop a method to purify these subpopulations by fluorescence-activated cell sorting and show that GFR?1+ and GFR?1- undifferentiated spermatogonia both demonstrate elevated transplantation activity, while differing principally in receptor tyrosine kinase signaling and cell cycle. We identify the cell surface molecule melanocyte cell adhesion molecule (MCAM) as differentially expressed in these populations and show that antibodies to MCAM allow isolation of highly enriched populations of GFR?1+ and GFR?1- spermatogonia from adult, wild-type mice. In germ cell culture, GFR?1- cells upregulate MCAM expression in response to glial cell line-derived neurotrophic factor (GDNF)/fibroblast growth factor (FGF) stimulation. In transplanted hosts, GFR?1- spermatogonia yield GFR?1+ spermatogonia and restore spermatogenesis, albeit at lower rates than their GFR?1+ counterparts. Together, these data provide support for a model of a stem cell pool in which the GFR?1+ and GFR?1- cells are closely related but show key cell-intrinsic differences and can interconvert between the two states based, in part, on access to niche factors.

    View details for PubMedID 29337115

  • Polycomb directs timely activation of germline genes in spermatogenesis. Genes & development Maezawa, S. n., Hasegawa, K. n., Yukawa, M. n., Sakashita, A. n., Alavattam, K. G., Andreassen, P. R., Vidal, M. n., Koseki, H. n., Barski, A. n., Namekawa, S. H. 2017; 31 (16): 1693?1703


    During spermatogenesis, a large number of germline genes essential for male fertility are coordinately activated. However, it remains unknown how timely activation of this group of germline genes is accomplished. Here we show that Polycomb-repressive complex 1 (PRC1) directs timely activation of germline genes during spermatogenesis. Inactivation of PRC1 in male germ cells results in the gradual loss of a stem cell population and severe differentiation defects, leading to male infertility. In the stem cell population, RNF2, the dominant catalytic subunit of PRC1, activates transcription of Sall4, which codes for a transcription factor essential for subsequent spermatogenic differentiation. Furthermore, RNF2 and SALL4 together occupy transcription start sites of germline genes in the stem cell population. Once differentiation commences, these germline genes are activated to enable the progression of spermatogenesis. Our study identifies a novel mechanism by which Polycomb directs the developmental process by activating a group of lineage-specific genes.

    View details for DOI 10.1101/gad.302000.117

    View details for PubMedID 28924034

  • High telomerase is a hallmark of undifferentiated spermatogonia and is required for maintenance of male germline stem cells. Genes & development Pech, M. F., Garbuzov, A., Hasegawa, K., Sukhwani, M., Zhang, R. J., Benayoun, B. A., Brockman, S. A., Lin, S., Brunet, A., Orwig, K. E., Artandi, S. E. 2015; 29 (23): 2420-2434


    Telomerase inactivation causes loss of the male germline in worms, fish, and mice, indicating a conserved dependence on telomere maintenance in this cell lineage. Here, using telomerase reverse transcriptase (Tert) reporter mice, we found that very high telomerase expression is a hallmark of undifferentiated spermatogonia, the mitotic population where germline stem cells reside. We exploited these high telomerase levels as a basis for purifying undifferentiated spermatogonia using fluorescence-activated cell sorting. Telomerase levels in undifferentiated spermatogonia and embryonic stem cells are comparable and much greater than in somatic progenitor compartments. Within the germline, we uncovered an unanticipated gradient of telomerase activity that also enables isolation of more mature populations. Transcriptomic comparisons of Tert(High) undifferentiated spermatogonia and Tert(Low) differentiated spermatogonia by RNA sequencing reveals marked differences in cell cycle and key molecular features of each compartment. Transplantation studies show that germline stem cell activity is confined to the Tert(High) cKit(-) population. Telomere shortening in telomerase knockout strains causes depletion of undifferentiated spermatogonia and eventual loss of all germ cells after undifferentiated spermatogonia drop below a critical threshold. These data reveal that high telomerase expression is a fundamental characteristic of germline stem cells, thus explaining the broad dependence on telomerase for germline immortality in metazoans.

    View details for DOI 10.1101/gad.271783.115

    View details for PubMedID 26584619

    View details for PubMedCentralID PMC4691947

  • RNA Binding Protein Nanos2 Organizes Post-transcriptional Buffering System to Retain Primitive State of Mouse Spermatogonial Stem Cells DEVELOPMENTAL CELL Zhou, Z., Shirakawa, T., Ohbo, K., Sada, A., Wu, Q., Hasegawa, K., Saba, R., Saga, Y. 2015; 34 (1): 96-107


    In many adult tissues, homeostasis relies on self-renewing stem cells that are primed for differentiation. The reconciliation mechanisms of these characteristics remain a fundamental question in stem cell biology. We propose that regulation at the post-transcriptional level is essential for homeostasis in murine spermatogonial stem cells (SSCs). Here, we show that Nanos2, an evolutionarily conserved RNA-binding protein, works with other cellular messenger ribonucleoprotein (mRNP) components to ensure the primitive status of SSCs through a dual mechanism that involves (1) direct recruitment and translational repression of genes that promote spermatogonial differentiation and (2) repression of the target of rapamycin complex 1 (mTORC1), a well-known negative pathway for SSC self-renewal, by sequestration of the core factor mTOR in mRNPs. This mechanism links mRNA turnover to mTORC1 signaling through Nanos2-containing mRNPs and establishes a post-transcriptional buffering system to facilitate SSC homeostasis in the fluctuating environment within the seminiferous tubule.

    View details for DOI 10.1016/j.devcel.2015.05.014

    View details for Web of Science ID 000357649300010

    View details for PubMedID 26120033

  • SCML2 Establishes the Male Germline Epigenome through Regulation of Histone H2A Ubiquitination DEVELOPMENTAL CELL Hasegawa, K., Sin, H., Maezawa, S., Broering, T. J., Kartashov, A. V., Alavattam, K. G., Ichijima, Y., Zhang, F., Bacon, W. C., Greis, K. D., Andreassen, P. R., Barski, A., Namekawa, S. H. 2015; 32 (5): 574-588


    Gametogenesis is dependent on the expression of germline-specific genes. However, it remains unknown how the germline epigenome is distinctly established from that of somatic lineages. Here we show that genes commonly expressed in somatic lineages and spermatogenesis-progenitor cells undergo repression in a genome-wide manner in late stages of the male germline and identify underlying mechanisms. SCML2, a germline-specific subunit of a Polycomb repressive complex 1 (PRC1), establishes the unique epigenome of the male germline through two distinct antithetical mechanisms. SCML2 works with PRC1 and promotes RNF2-dependent ubiquitination of H2A, thereby marking somatic/progenitor genes on autosomes for repression. Paradoxically, SCML2 also prevents RNF2-dependent ubiquitination of H2A on sex chromosomes during meiosis, thereby enabling unique epigenetic programming of sex chromosomes for male reproduction. Our results reveal divergent mechanisms involving a shared regulator by which the male germline epigenome is distinguished from that of the soma and progenitor cells.

    View details for DOI 10.1016/j.devcel.2015.01.014

    View details for Web of Science ID 000350989300007

    View details for PubMedID 25703348

    View details for PubMedCentralID PMC4391279

  • Poised chromatin and bivalent domains facilitate the mitosis-to-meiosis transition in the male germline. BMC biology Sin, H., Kartashov, A. V., Hasegawa, K., Barski, A., Namekawa, S. H. 2015; 13: 53-?


    The male germline transcriptome changes dramatically during the mitosis-to-meiosis transition to activate late spermatogenesis genes and to transiently suppress genes commonly expressed in somatic lineages and spermatogenesis progenitor cells, termed somatic/progenitor genes.These changes reflect epigenetic regulation. Induction of late spermatogenesis genes during spermatogenesis is facilitated by poised chromatin established in the stem cell phases of spermatogonia, whereas silencing of somatic/progenitor genes during meiosis and postmeiosis is associated with formation of bivalent domains which also allows the recovery of the somatic/progenitor program after fertilization. Importantly, during spermatogenesis mechanisms of epigenetic regulation on sex chromosomes are different from autosomes: X-linked somatic/progenitor genes are suppressed by meiotic sex chromosome inactivation without deposition of H3K27me3.Our results suggest that bivalent H3K27me3 and H3K4me2/3 domains are not limited to developmental promoters (which maintain bivalent domains that are silent throughout the reproductive cycle), but also underlie reversible silencing of somatic/progenitor genes during the mitosis-to-meiosis transition in late spermatogenesis.

    View details for DOI 10.1186/s12915-015-0159-8

    View details for PubMedID 26198001

    View details for PubMedCentralID PMC4508805

  • FGF8-FGFR1 Signaling Acts as a Niche Factor for Maintaining Undifferentiated Spermatogonia in the Mouse BIOLOGY OF REPRODUCTION Hasegawa, K., Saga, Y. 2014; 91 (6)


    In mammalian testes, spermatogonial stem cells (SSCs) maintain spermatogenesis over a long period of time by undergoing self-renewal and differentiation. SSCs are among the most primitive of spermatogenic cells (undifferentiated spermatogonia), and their activities are strictly regulated by extrinsic niche factors. However, the factors that constitute a testicular niche remain poorly understood. In this study, we demonstrate that fibroblast growth factor (FGF) signaling maintains undifferentiated spermatogonia through activating ERK1/2 signaling in vivo. Undifferentiated spermatogonia comprise GFRA1(+) and NANOS3(+) subpopulations, which are likely to undergo self-renewal and enter the differentiation pathway, respectively. In the testis, Fgfr1 was expressed in the entire population of undifferentiated spermatogonia, and deleting FGFR1 in spermatogenic cells partially inactivated ERK1/2 and resulted in reduced numbers of both GFRA1(+) and NANOS3(+) cells. In addition, Fgf8 was expressed in spermatogenic cells, and loss- and gain-of-function models of FGF8 demonstrated that FGF8 positively regulated the numbers of undifferentiated spermatogonia through FGFR1, particularly among NANOS3(+) cells. Finally we show a possible involvement of FGF signaling in the reversion from NANOS3(+) into GFRA1(+) undifferentiated spermatogonia. Taken together, our data suggest that FGF signaling is an important component of the testicular niche and has a unique function for maintaining undifferentiated spermatogonia.

    View details for DOI 10.1095/biolreprod.114.121012

    View details for Web of Science ID 000355603600003

    View details for PubMedID 25359900

  • BRCA1 establishes DNA damage signaling and pericentric heterochromatin of the X chromosome in male meiosis JOURNAL OF CELL BIOLOGY Broering, T. J., Alavattam, K. G., Sadreyev, R. I., Ichijima, Y., Kato, Y., Hasegawa, K., Camerini-Otero, R. D., Lee, J. T., Andreassen, P. R., Namekawa, S. H. 2014; 205 (5): 663-675


    During meiosis, DNA damage response (DDR) proteins induce transcriptional silencing of unsynapsed chromatin, including the constitutively unsynapsed XY chromosomes in males. DDR proteins are also implicated in double strand break repair during meiotic recombination. Here, we address the function of the breast cancer susceptibility gene Brca1 in meiotic silencing and recombination in mice. Unlike in somatic cells, in which homologous recombination defects of Brca1 mutants are rescued by 53bp1 deletion, the absence of 53BP1 did not rescue the meiotic failure seen in Brca1 mutant males. Further, BRCA1 promotes amplification and spreading of DDR components, including ATR and TOPBP1, along XY chromosome axes and promotes establishment of pericentric heterochromatin on the X chromosome. We propose that BRCA1-dependent establishment of X-pericentric heterochromatin is critical for XY body morphogenesis and subsequent meiotic progression. In contrast, BRCA1 plays a relatively minor role in meiotic recombination, and female Brca1 mutants are fertile. We infer that the major meiotic role of BRCA1 is to promote the dramatic chromatin changes required for formation and function of the XY body.

    View details for DOI 10.1083/jcb.201311050

    View details for Web of Science ID 000337210800007

    View details for PubMedID 24914237

  • MEK/ERK Signaling Directly and Indirectly Contributes to the Cyclical Self-Renewal of Spermatogonial Stem Cells STEM CELLS Hasegawa, K., Namekawa, S. H., Saga, Y. 2013; 31 (11): 2517-2527


    Coordination of stem cell fate is regulated by extrinsic niche signals and stem cell intrinsic factors. In mammalian testes, spermatogonial stem cells maintain constant production of abundant spermatozoa by alternating between self-renewal and differentiation at regular intervals according to a periodical program known as the seminiferous epithelial cycle. Although retinoic acid (RA) signaling has been suggested to direct the cyclical differentiation of spermatogonial stem cells, it remains largely unclear how their cycle-dependent self-renewal/proliferation is regulated. Here, we show that MEK/ERK signaling contributes to the cyclical activity of spermatogonial stem cells. We found that ERK1/2 is periodically activated in Sertoli cells during the stem cell self-renewal/proliferation phase, and that MEK/ERK signaling is required for the stage-related expression of the critical niche factor GDNF. In addition, ERK1/2 is activated in GFR?1-positive spermatogonial stem cells under the control of GDNF and prevent them from being differentiated. These results suggest that MEK/ERK signaling directly and indirectly maintains spermatogonial stem cells by mediating a signal that promotes their periodical self-renewal/proliferation. Conversely, RA signaling directly and indirectly induces differentiation of spermatogonial stem cells. We propose that temporally regulated activations of RA signaling and a signal regulating MEK/ERK antagonistically coordinates the cycle-related activity of spermatogonial stem cells.

    View details for DOI 10.1002/stem.1486

    View details for Web of Science ID 000327025600021

    View details for PubMedID 23897718

  • Retinoic acid signaling in Sertoli cells regulates organization of the blood-testis barrier through cyclical changes in gene expression DEVELOPMENT Hasegawa, K., Saga, Y. 2012; 139 (23): 4347-4355


    Mammalian spermatogenesis contributes a constant production of large numbers of spermatozoa, which is achieved by a cyclically regulated program known as the seminiferous epithelial cycle. Sertoli cells, functionally unique somatic cells, create a microenvironment to support the continuous differentiation of germ cells especially through the formation of a blood-testis barrier (BTB). The BTB is essential for maintaining homeostasis in seminiferous tubules and opens transiently at stages VII-VIII to ensure constant differentiation of spermatogenic cells. However, it is poorly understood how the dynamic organization of BTB is regulated. In our current study, we find that the overexpression of a dominant-negative form of RAR? (dnRAR?) in Sertoli cells disrupts the BTB at stages VII-XII and causes the large-scale apoptosis of differentiating germ cells. These abnormal events are found to be associated with cyclical gene expression changes in Sertoli cells, which can be represented by abnormal activation and repression of genes showing peaks of expression during stages I-VI and VII-XII, respectively. We find that one such gene, Ocln, encoding a tight junction component, partly contributes to the BTB disruption caused by dnRAR?. Taken together, our data suggest that the cyclical activation of RA signaling in Sertoli cells during stages VII-XII contributes to a periodic organization of the BTB through changes in stage-dependent gene expression.

    View details for DOI 10.1242/dev.080119

    View details for Web of Science ID 000310780300007

    View details for PubMedID 23095883

  • NANOS2 Acts Downstream of Glial Cell Line-Derived Neurotrophic Factor Signaling to Suppress Differentiation of Spermatogonial Stem Cells STEM CELLS Sada, A., Hasegawa, K., Pin, P. H., Saga, Y. 2012; 30 (2): 280-291


    Stem cells are maintained by both stem cell-extrinsic niche signals and stem cell-intrinsic factors. During murine spermatogenesis, glial cell line-derived neurotrophic factor (GDNF) signal emanated from Sertoli cells and germ cell-intrinsic factor NANOS2 represent key regulators for the maintenance of spermatogonial stem cells. However, it remains unclear how these factors intersect in stem cells to control their cellular state. Here, we show that GDNF signaling is essential to maintain NANOS2 expression, and overexpression of Nanos2 can alleviate the stem cell loss phenotype caused by the depletion of Gfra1, a receptor for GDNF. By using an inducible Cre-loxP system, we show that NANOS2 expression is downregulated upon the conditional knockout (cKO) of Gfra1, while ectopic expression of Nanos2 in GFRA1-negative spermatogonia does not induce de novo GFRA1 expression. Furthermore, overexpression of Nanos2 in the Gfra1-cKO testes prevents precocious differentiation of the Gfra1-knockout stem cells and partially rescues the stem cell loss phenotypes of Gfra1-deficient mice, indicating that the stem cell differentiation can be suppressed by NANOS2 even in the absence of GDNF signaling. Taken together, we suggest that NANOS2 acts downstream of GDNF signaling to maintain undifferentiated state of spermatogonial stem cells.

    View details for DOI 10.1002/stem.790

    View details for Web of Science ID 000299209200019

    View details for PubMedID 22102605

  • Notch Signaling in Sertoli Cells Regulates Cyclical Gene Expression of Hes1 but Is Dispensable for Mouse Spermatogenesis MOLECULAR AND CELLULAR BIOLOGY Hasegawa, K., Okamura, Y., Saga, Y. 2012; 32 (1): 206-215


    Mammalian spermatogenesis is a highly regulated system dedicated to the continuous production of spermatozoa from spermatogonial stem cells, and the process largely depends on microenvironments created by Sertoli cells, unique somatic cells that reside within a seminiferous tubule. Spermatogenesis progresses with a cyclical program known as the "seminiferous epithelial cycle," which is accompanied with cyclical gene expression changes in Sertoli cells. However, it is unclear how the cyclicity in Sertoli cells is regulated. Here, we report that Notch signaling, which is known to play an important role for germ cell development in Drosophila and Caenorhabditis elegans, is cyclically activated in Sertoli cells and regulates stage-dependent gene expression of Hes1. To elucidate the regulatory mechanism of stage-dependent Hes1 expression and the role of Notch signaling in mouse spermatogenesis, we inactivated Notch signaling in Sertoli cells by deleting protein O-fucosyltransferase 1 (Pofut1), using the cre-loxP system, and found that stage-dependent Hes1 expression was dependent on the activation of Notch signaling. Unexpectedly, however, spermatogenesis proceeded normally. Our results thus indicate that Notch signaling regulates cyclical gene expression in Sertoli cells but is dispensable for mouse spermatogenesis. This highlights the evolutionary divergences in regulation of germ cell development.

    View details for DOI 10.1128/MCB.06063-11

    View details for Web of Science ID 000298366000018

    View details for PubMedID 22037762

  • c-Maf plays a crucial role for the definitive erythropoiesis that accompanies erythroblastic island formation in the fetal liver BLOOD Kusakabe, M., Hasegawa, K., Hamada, M., Nakamura, M., Ohsumi, T., Suzuki, H., Mai Thi Nhu Tran, T. N., Kudo, T., Uchida, K., Ninomiya, H., Chiba, S., Takahashi, S. 2011; 118 (5): 1374-1385


    c-Maf is one of the large Maf (musculoaponeurotic fibrosarcoma) transcription factors that belong to the activated protein-1 super family of basic leucine zipper proteins. Despite its overexpression in hematologic malignancies, the physiologic roles c-Maf plays in normal hematopoiesis have been largely unexplored. On a C57BL/6J background, c-Maf(-/-) embryos succumbed from severe erythropenia between embryonic day (E) 15 and E18. Flow cytometric analysis of fetal liver cells showed that the mature erythroid compartments were significantly reduced in c-Maf(-/-) embryos compared with c-Maf(+/+) littermates. Interestingly, the CFU assay indicated there was no significant difference between c-Maf(+/+) and c-Maf(-/-) fetal liver cells in erythroid colony counts. This result indicated that impaired definitive erythropoiesis in c-Maf(-/-) embryos is because of a non-cell-autonomous effect, suggesting a defective erythropoietic microenvironment in the fetal liver. As expected, the number of erythroblasts surrounding the macrophages in erythroblastic islands was significantly reduced in c-Maf(-/-) embryos. Moreover, decreased expression of VCAM-1 was observed in c-Maf(-/-) fetal liver macrophages. In conclusion, these results strongly suggest that c-Maf is crucial for definitive erythropoiesis in fetal liver, playing an important role in macrophages that constitute erythroblastic islands.

    View details for DOI 10.1182/blood-2010-08-300400

    View details for Web of Science ID 000293510000031

    View details for PubMedID 21628412

  • c-Maf is essential for the F4/80 expression in macrophages in vivo GENE Nakamura, M., Hamada, M., Hasegawa, K., Kusakabe, M., Suzuki, H., Greaves, D. R., Moriguchi, T., Kudo, T., Takahashi, S. 2009; 445 (1-2): 66-72


    c-Maf, which is one of the large Maf transcription factors, can bind to Maf recognition element (MARE) and activates transcription of target genes. Although c-Maf is expressed in macrophages and directly regulates the expression of interleukin-10, detailed information regarding its function in the null mutant phenotype of tissue macrophages remain unknown. In this study, we demonstrated that c-Maf is specifically expressed in the F4/80 positive fetal liver and adult macrophages. The expression of F4/80, which is a tissue macrophage-specific seven trans-membrane receptor, was dramatically suppressed in the c-Maf-deficient macrophage, whereas the expression of Mac-1 was not affected, suggesting that c-Maf is not necessary for the lineage commitment of macrophages. Luciferase reporter and EMSA showed that c-Maf directly regulates the expression of F4/80 by interacting with the half-MARE site of the F4/80 promoter. These results suggest that c-Maf is required for the F4/80 expression in macrophages in vivo.

    View details for DOI 10.1016/j.gene.2009.06.003

    View details for Web of Science ID 000269047900007

    View details for PubMedID 19539733

  • Runx1 is involved in primitive erythropoiesis in the mouse BLOOD Yokomizo, T., Hasegawa, K., Ishitobi, H., Osato, M., Erna, M., Lto, Y., Yamamoto, M., Takahashi, S. 2008; 111 (8): 4075-4080


    Targeted disruption of the Runx1/ AML1 gene in mice has demonstrated that it is required for the emergence of definitive hematopoietic cells but that it is not essential for the formation of primitive erythrocytes. These findings led to the conclusion that Runx1 is a stage-specific transcription factor acting only during definitive hematopoiesis. However, the zebrafish and Xenopus homologs of Runx1 have been shown to play roles in primitive hematopoiesis, suggesting that mouse Runx1 might also be involved in the development of primitive lineages. In this study, we show that primitive erythrocytes in Runx1(-/-) mice display abnormal morphology and reduced expression of Ter119, Erythroid Kruppel-like factor (EKLF, KLF1), and GATA-1. These results suggest that mouse Runx1 plays a role in the development of both primitive and definitive hematopoietic cells.

    View details for DOI 10.1182/blood-2007-05-091637

    View details for Web of Science ID 000255134700029

    View details for PubMedID 18250229

  • MafB is essential for renal development and F4/80 expression in macrophages MOLECULAR AND CELLULAR BIOLOGY Moriguchi, T., Hamada, M., Morito, N., Terunuma, T., Hasegawa, K., Zhang, C., Yokomizo, T., Esaki, R., Kuroda, E., Yoh, K., Kudo, T., Nagata, M., Greaves, D. R., Engel, J. D., Yamamoto, M., Takahashi, S. 2006; 26 (15): 5715-5727


    MafB is a member of the large Maf family of transcription factors that share similar basic region/leucine zipper DNA binding motifs and N-terminal activation domains. Although it is well known that MafB is specifically expressed in glomerular epithelial cells (podocytes) and macrophages, characterization of the null mutant phenotype in these tissues has not been previously reported. To investigate suspected MafB functions in the kidney and in macrophages, we generated mafB/green fluorescent protein (GFP) knock-in null mutant mice. MafB homozygous mutants displayed renal dysgenesis with abnormal podocyte differentiation as well as tubular apoptosis. Interestingly, these kidney phenotypes were associated with diminished expression of several kidney disease-related genes. In hematopoietic cells, GFP fluorescence was observed in both Mac-1- and F4/80-expressing macrophages in the fetal liver. Interestingly, F4/80 expression in macrophages was suppressed in the homozygous mutant, although development of the Mac-1-positive macrophage population was unaffected. In primary cultures of fetal liver hematopoietic cells, MafB deficiency was found to dramatically suppress F4/80 expression in nonadherent macrophages, whereas the Mac-1-positive macrophage population developed normally. These results demonstrate that MafB is essential for podocyte differentiation, renal tubule survival, and F4/80 maturation in a distinct subpopulation of nonadherent mature macrophages.

    View details for DOI 10.1128/MCB.00001-06

    View details for Web of Science ID 000239286600015

    View details for PubMedID 16847325

  • MafA is a key regulator of glucose-stimulated insulin secretion MOLECULAR AND CELLULAR BIOLOGY Zhang, C., Moriguchi, T., Kajihara, M., Esaki, R., Harada, A., Shimohata, H., Oishi, H., Hamada, M., Morito, N., Hasegawa, K., Kudo, T., Engel, J. D., Yamamoto, M., Takahashi, S. 2005; 25 (12): 4969-4976


    MafA is a transcription factor that binds to the promoter in the insulin gene and has been postulated to regulate insulin transcription in response to serum glucose levels, but there is no current in vivo evidence to support this hypothesis. To analyze the role of MafA in insulin transcription and glucose homeostasis in vivo, we generated MafA-deficient mice. Here we report that MafA mutant mice display intolerance to glucose and develop diabetes mellitus. Detailed analyses revealed that glucose-, arginine-, or KCl-stimulated insulin secretion from pancreatic beta cells is severely impaired, although insulin content per se is not significantly affected. MafA-deficient mice also display age-dependent pancreatic islet abnormalities. Further analysis revealed that insulin 1, insulin 2, Pdx1, Beta2, and Glut-2 transcripts are diminished in MafA-deficient mice. These results show that MafA is a key regulator of glucose-stimulated insulin secretion in vivo.

    View details for DOI 10.1128/MCB.25.12.4969-4976.2005

    View details for Web of Science ID 000229605900015

    View details for PubMedID 15923615

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