The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform
Rabindranath Fuente - One of the best experts on this subject based on the ideXlab platform.
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Chromatin configuration and epigenetic landscape at the sex Chromosome Bivalent during equine spermatogenesis
Chromosoma, 2011Co-Authors: Claudia Baumann, Christopher M. Daly, Maria M. Viveiros, Sue M. Mcdonnell, Rabindranath FuenteAbstract:Pairing of the sex Chromosomes during mammalian meiosis is characterized by the formation of a unique heterochromatin structure at the XY body. The mechanisms underlying the formation of this nuclear domain are reportedly highly conserved from marsupials to mammals. In this study, we demonstrate that in contrast to all eutherian species studied to date, partial synapsis of the heterologous sex Chromosomes during pachytene stage in the horse is not associated with the formation of a typical macrochromatin domain at the XY body. While phosphorylated histone H2AX (γH2AX) and macroH2A1.2 are present as a diffuse signal over the entire macrochromatin domain in mouse pachytene spermatocytes, γH2AX, macroH2A1.2, and the cohesin subunit SMC3 are preferentially enriched at meiotic sex Chromosome cores in equine spermatocytes. Moreover, although several histone modifications associated with this nuclear domain in the mouse such as H3K4me2 and ubH2A are conspicuously absent in the equine XY body, prominent RNA polymerase II foci persist at the sex Chromosomes. Thus, the localization of key marker proteins and histone modifications associated with the XY body in the horse differs significantly from all other mammalian systems described. These results demonstrate that the epigenetic landscape and heterochromatinization of the equine XY body might be regulated by alternative mechanisms and that some features of XY body formation may be evolutionary divergent in the domestic horse. We propose equine spermatogenesis as a unique model system for the study of the regulatory networks leading to the epigenetic control of gene expression during XY body formation.
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Persistence of histone H2AX phosphorylation after meiotic Chromosome synapsis and abnormal centromere cohesion in poly (ADP-ribose) polymerase (Parp-1) null oocytes.
Developmental biology, 2009Co-Authors: Feikun Yang, Claudia Baumann, Rabindranath FuenteAbstract:In spite of the impact of aneuploidy on human health little is known concerning the molecular mechanisms involved in the formation of structural or numerical Chromosome abnormalities during meiosis. Here, we provide novel evidence indicating that lack of PARP-1 function during oogenesis predisposes the female gamete to genome instability. During prophase I of meiosis, a high proportion of Parp-1((-/-)) mouse oocytes exhibit a spectrum of meiotic defects including incomplete homologous Chromosome synapsis or persistent histone H2AX phosphorylation in fully synapsed Chromosomes at the late pachytene stage. Moreover, the X Chromosome Bivalent is also prone to exhibit persistent double strand DNA breaks (DSBs). In striking contrast, such defects were not detected in mutant pachytene spermatocytes. In fully-grown wild type oocytes at the germinal vesicle stage, PARP-1 protein associates with nuclear speckles and upon meiotic resumption, undergoes a striking re-localization towards spindle poles as well as pericentric heterochromatin domains at the metaphase II stage. Notably, a high proportion of in vivo matured Parp-1((-/-)) oocytes show lack of recruitment of the kinetochore-associated protein BUB3 to centromeric domains and fail to maintain metaphase II arrest. Defects in chromatin modifications in the form of persistent histone H2AX phosphorylation during prophase I of meiosis and deficient sister chromatid cohesion during metaphase II predispose mutant oocytes to premature anaphase II onset upon removal from the oviductal environment. Our results indicate that PARP-1 plays a critical role in the maintenance of Chromosome stability at key stages of meiosis in the female germ line. Moreover, in the metaphase II stage oocyte PARP-1 is required for the regulation of centromere structure and function through a mechanism that involves the recruitment of BUB3 protein to centromeric domains.
Claudia Baumann - One of the best experts on this subject based on the ideXlab platform.
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Chromatin configuration and epigenetic landscape at the sex Chromosome Bivalent during equine spermatogenesis
Chromosoma, 2011Co-Authors: Claudia Baumann, Christopher M. Daly, Maria M. Viveiros, Sue M. Mcdonnell, Rabindranath FuenteAbstract:Pairing of the sex Chromosomes during mammalian meiosis is characterized by the formation of a unique heterochromatin structure at the XY body. The mechanisms underlying the formation of this nuclear domain are reportedly highly conserved from marsupials to mammals. In this study, we demonstrate that in contrast to all eutherian species studied to date, partial synapsis of the heterologous sex Chromosomes during pachytene stage in the horse is not associated with the formation of a typical macrochromatin domain at the XY body. While phosphorylated histone H2AX (γH2AX) and macroH2A1.2 are present as a diffuse signal over the entire macrochromatin domain in mouse pachytene spermatocytes, γH2AX, macroH2A1.2, and the cohesin subunit SMC3 are preferentially enriched at meiotic sex Chromosome cores in equine spermatocytes. Moreover, although several histone modifications associated with this nuclear domain in the mouse such as H3K4me2 and ubH2A are conspicuously absent in the equine XY body, prominent RNA polymerase II foci persist at the sex Chromosomes. Thus, the localization of key marker proteins and histone modifications associated with the XY body in the horse differs significantly from all other mammalian systems described. These results demonstrate that the epigenetic landscape and heterochromatinization of the equine XY body might be regulated by alternative mechanisms and that some features of XY body formation may be evolutionary divergent in the domestic horse. We propose equine spermatogenesis as a unique model system for the study of the regulatory networks leading to the epigenetic control of gene expression during XY body formation.
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Persistence of histone H2AX phosphorylation after meiotic Chromosome synapsis and abnormal centromere cohesion in poly (ADP-ribose) polymerase (Parp-1) null oocytes.
Developmental biology, 2009Co-Authors: Feikun Yang, Claudia Baumann, Rabindranath FuenteAbstract:In spite of the impact of aneuploidy on human health little is known concerning the molecular mechanisms involved in the formation of structural or numerical Chromosome abnormalities during meiosis. Here, we provide novel evidence indicating that lack of PARP-1 function during oogenesis predisposes the female gamete to genome instability. During prophase I of meiosis, a high proportion of Parp-1((-/-)) mouse oocytes exhibit a spectrum of meiotic defects including incomplete homologous Chromosome synapsis or persistent histone H2AX phosphorylation in fully synapsed Chromosomes at the late pachytene stage. Moreover, the X Chromosome Bivalent is also prone to exhibit persistent double strand DNA breaks (DSBs). In striking contrast, such defects were not detected in mutant pachytene spermatocytes. In fully-grown wild type oocytes at the germinal vesicle stage, PARP-1 protein associates with nuclear speckles and upon meiotic resumption, undergoes a striking re-localization towards spindle poles as well as pericentric heterochromatin domains at the metaphase II stage. Notably, a high proportion of in vivo matured Parp-1((-/-)) oocytes show lack of recruitment of the kinetochore-associated protein BUB3 to centromeric domains and fail to maintain metaphase II arrest. Defects in chromatin modifications in the form of persistent histone H2AX phosphorylation during prophase I of meiosis and deficient sister chromatid cohesion during metaphase II predispose mutant oocytes to premature anaphase II onset upon removal from the oviductal environment. Our results indicate that PARP-1 plays a critical role in the maintenance of Chromosome stability at key stages of meiosis in the female germ line. Moreover, in the metaphase II stage oocyte PARP-1 is required for the regulation of centromere structure and function through a mechanism that involves the recruitment of BUB3 protein to centromeric domains.
Gedalia Paz - One of the best experts on this subject based on the ideXlab platform.
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Use of sex Chromosome Bivalent pairing in spermatocytes of nonobstructive azoospermic men for the prediction of successful sperm retrieval
Fertility and sterility, 2006Co-Authors: Leah Yogev, Sandra E. Kleiman, Ron Hauser, Amnon Botchan, Haim Yavetz, Batia Bar-shira Maymon, Einav Zeharia, Gedalia PazAbstract:Objective To find the most informative method of XY Bivalent detection for spermatozoa presence in testicular tissue of nonobstructive azoospermic men. Design Prospective study. Setting Institute for the Study of Fertility, affiliated with a university medical faculty. Patient(s) Thirty-five men with azoospermia, divided into subgroups: complete maturation arrest (n = 10), mixed atrophy (n = 14), and obstructive azoospermia (n = 11). Intervention(s) Testicular tissue biopsies for sperm extraction. Main Outcome Measure(s) Histopathologic and cytology analyses and the presence of XY Bivalent formation by fluorescence in situ hybridization probes for centromere and subtelomere regions. Immunostaining of γ-H2AX for sex body (SB) identification was also performed. Result(s) Percentage of spermatocytes with X-Y pairing, determined by the paired short arms pseudoautosomal region, was significantly higher than percentage of spermatocytes with long arm telomeres in proximity in all three groups. The parameter of q telomeres in proximity was the most sensitive index to distinguish one group from the other. Stained SB by γ-H2AX was found to be the most informative for the prediction of successful sperm retrieval. Conclusion(s) Alignment of the X and Y axes that occurs in the late zygotene stage probably precedes the stage in which the SB is stained by γ-H2AX. Consequently, because of the nonhomogeneity of the testis, when histology raises suspicion of complete maturation arrest percentage of spermatocytes with stained SB is the most informative parameter for sperm presence on sperm retrieval.
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Reduced Human Germ Cell-Less (HGCL) Expression in Azoospermic Men With Severe Germinal Cell Impairment
Journal of andrology, 2003Co-Authors: Sandra E. Kleiman, Leah Yogev, Einav Nili Gal-yam, Ron Hauser, Ronni Gamzu, Amnon Botchan, Gedalia Paz, Haim Yavetz, Batia Bar-shira Maymon, Letizia SchreiberAbstract:Germ cell-less (GCL) protein is a nuclear envelope protein highly conserved between the mammalian and Drosophila orthologues. In Drosophila, maternal GCL protein is required to establish the germ lineage during embryonic development. In mammals, it is suggested that the GCL function is mainly in spermatogenesis and that it might be related to the ability of mouse GCL to repress transcription. Using reverse transcriptase-polymerase chain reaction analyses, we investigated the role of human GCL (HGCL) in spermatogenesis by studying its expression in the testicular tissue of 67 azoospermic men with normal karyotype and no Y-Chromosome microdeletion. Their testicular biopsy specimens underwent meticulous histological and cytological analysis as well as molecular analysis with various markers of spermatogenesis (RBM1, DAZ, and CDY1). The rate of X-Y and 18 Chromosome Bivalent formation during meiosis was additionally assessed in 22 of these biopsy specimens and correlated to HGCL expression. Expression of HGCL was affected in parallel with the severity of testicular impairment found. Defective sperm motility was associated with the absence of HGCL. Nevertheless, the absence of HGCL expression did not influence the normal process of Chromosome Bivalent formation in meiosis. Our results suggest that HGCL is not essential for the chromosomal events of meiosis but might be involved in later aspects of spermatogenesis.
Leah Yogev - One of the best experts on this subject based on the ideXlab platform.
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Use of sex Chromosome Bivalent pairing in spermatocytes of nonobstructive azoospermic men for the prediction of successful sperm retrieval
Fertility and sterility, 2006Co-Authors: Leah Yogev, Sandra E. Kleiman, Ron Hauser, Amnon Botchan, Haim Yavetz, Batia Bar-shira Maymon, Einav Zeharia, Gedalia PazAbstract:Objective To find the most informative method of XY Bivalent detection for spermatozoa presence in testicular tissue of nonobstructive azoospermic men. Design Prospective study. Setting Institute for the Study of Fertility, affiliated with a university medical faculty. Patient(s) Thirty-five men with azoospermia, divided into subgroups: complete maturation arrest (n = 10), mixed atrophy (n = 14), and obstructive azoospermia (n = 11). Intervention(s) Testicular tissue biopsies for sperm extraction. Main Outcome Measure(s) Histopathologic and cytology analyses and the presence of XY Bivalent formation by fluorescence in situ hybridization probes for centromere and subtelomere regions. Immunostaining of γ-H2AX for sex body (SB) identification was also performed. Result(s) Percentage of spermatocytes with X-Y pairing, determined by the paired short arms pseudoautosomal region, was significantly higher than percentage of spermatocytes with long arm telomeres in proximity in all three groups. The parameter of q telomeres in proximity was the most sensitive index to distinguish one group from the other. Stained SB by γ-H2AX was found to be the most informative for the prediction of successful sperm retrieval. Conclusion(s) Alignment of the X and Y axes that occurs in the late zygotene stage probably precedes the stage in which the SB is stained by γ-H2AX. Consequently, because of the nonhomogeneity of the testis, when histology raises suspicion of complete maturation arrest percentage of spermatocytes with stained SB is the most informative parameter for sperm presence on sperm retrieval.
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Reduced Human Germ Cell-Less (HGCL) Expression in Azoospermic Men With Severe Germinal Cell Impairment
Journal of andrology, 2003Co-Authors: Sandra E. Kleiman, Leah Yogev, Einav Nili Gal-yam, Ron Hauser, Ronni Gamzu, Amnon Botchan, Gedalia Paz, Haim Yavetz, Batia Bar-shira Maymon, Letizia SchreiberAbstract:Germ cell-less (GCL) protein is a nuclear envelope protein highly conserved between the mammalian and Drosophila orthologues. In Drosophila, maternal GCL protein is required to establish the germ lineage during embryonic development. In mammals, it is suggested that the GCL function is mainly in spermatogenesis and that it might be related to the ability of mouse GCL to repress transcription. Using reverse transcriptase-polymerase chain reaction analyses, we investigated the role of human GCL (HGCL) in spermatogenesis by studying its expression in the testicular tissue of 67 azoospermic men with normal karyotype and no Y-Chromosome microdeletion. Their testicular biopsy specimens underwent meticulous histological and cytological analysis as well as molecular analysis with various markers of spermatogenesis (RBM1, DAZ, and CDY1). The rate of X-Y and 18 Chromosome Bivalent formation during meiosis was additionally assessed in 22 of these biopsy specimens and correlated to HGCL expression. Expression of HGCL was affected in parallel with the severity of testicular impairment found. Defective sperm motility was associated with the absence of HGCL. Nevertheless, the absence of HGCL expression did not influence the normal process of Chromosome Bivalent formation in meiosis. Our results suggest that HGCL is not essential for the chromosomal events of meiosis but might be involved in later aspects of spermatogenesis.
Christopher M. Daly - One of the best experts on this subject based on the ideXlab platform.
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Chromatin configuration and epigenetic landscape at the sex Chromosome Bivalent during equine spermatogenesis
Chromosoma, 2011Co-Authors: Claudia Baumann, Christopher M. Daly, Maria M. Viveiros, Sue M. Mcdonnell, Rabindranath FuenteAbstract:Pairing of the sex Chromosomes during mammalian meiosis is characterized by the formation of a unique heterochromatin structure at the XY body. The mechanisms underlying the formation of this nuclear domain are reportedly highly conserved from marsupials to mammals. In this study, we demonstrate that in contrast to all eutherian species studied to date, partial synapsis of the heterologous sex Chromosomes during pachytene stage in the horse is not associated with the formation of a typical macrochromatin domain at the XY body. While phosphorylated histone H2AX (γH2AX) and macroH2A1.2 are present as a diffuse signal over the entire macrochromatin domain in mouse pachytene spermatocytes, γH2AX, macroH2A1.2, and the cohesin subunit SMC3 are preferentially enriched at meiotic sex Chromosome cores in equine spermatocytes. Moreover, although several histone modifications associated with this nuclear domain in the mouse such as H3K4me2 and ubH2A are conspicuously absent in the equine XY body, prominent RNA polymerase II foci persist at the sex Chromosomes. Thus, the localization of key marker proteins and histone modifications associated with the XY body in the horse differs significantly from all other mammalian systems described. These results demonstrate that the epigenetic landscape and heterochromatinization of the equine XY body might be regulated by alternative mechanisms and that some features of XY body formation may be evolutionary divergent in the domestic horse. We propose equine spermatogenesis as a unique model system for the study of the regulatory networks leading to the epigenetic control of gene expression during XY body formation.