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Many X-linked microRNAs escape meiotic sex chromosome inactivation.

ABSTRACT: Meiotic sex chromosome inactivation (MSCI) during spermatogenesis is characterized by transcriptional silencing of genes on both the X and Y chromosomes in mid-to-late pachytene spermatocytes. MSCI is believed to result from meiotic silencing of unpaired DNA because the X and Y chromosomes remain largely unpaired throughout first meiotic prophase. However, unlike X-chromosome inactivation in female embryonic cells, where 25-30% of X-linked structural genes have been reported to escape inactivation, previous microarray- and RT-PCR-based studies of expression of >364 X-linked mRNA-encoding genes during spermatogenesis have failed to reveal any X-linked gene that escapes the silencing effects of MSCI in primary spermatocytes. Here we show that many X-linked miRNAs are transcribed and processed in pachytene spermatocytes. This unprecedented escape from MSCI by these X-linked miRNAs suggests that they may participate in a critical function at this stage of spermatogenesis, including the possibility that they contribute to the process of MSCI itself, or that they may be essential for post-transcriptional regulation of autosomal mRNAs during the late meiotic and early postmeiotic stages of spermatogenesis.

SUBMITTER: Song R

PROVIDER: S-EPMC2723799 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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Many X-linked microRNAs escape meiotic sex chromosome inactivation.

Song Rui R Ro Seungil S Michaels Jason D JD Park Chanjae C McCarrey John R JR Yan Wei W

Nature genetics 20090322 4

Meiotic sex chromosome inactivation (MSCI) during spermatogenesis is characterized by transcriptional silencing of genes on both the X and Y chromosomes in mid-to-late pachytene spermatocytes. MSCI is believed to result from meiotic silencing of unpaired DNA because the X and Y chromosomes remain largely unpaired throughout first meiotic prophase. However, unlike X-chromosome inactivation in female embryonic cells, where 25-30% of X-linked structural genes have been reported to escape inactivati ...[more]

PMID: 19305411

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Project description:Aortic valve stenosis (AVS) is a sexually dimorphic disease, with women often presenting with sustained fibrosis and men with more extensive calcification. However, the intracellular molecular mechanisms that drive these clinically important sex differences remain under explored. Hydrogel scaffolds were designed to recapitulate key aspects of the valve tissue microenvironment and serve as a platform for culture of sex-specific valvular interstitial cells (VICs; precursors to pro-fibrotic myofibroblasts). The hydrogel culture system was used to interrogate intracellular pathways involved in sex-dependent VIC-to-myofibroblast activation and deactivation. RNA-seq was used to define pathways likely to be involved in driving sex-dependent activation. Interventions using small molecule inhibitors were performed to provide mechanistic insight into sex-specific cellular responses to microenvironmental cues, including matrix stiffness and exogenously delivered biochemical factors. In both healthy porcine and human aortic valves, female leaflets had higher baseline activation of the myofibroblast marker, α-smooth muscle actin (α-SMA), compared to male leaflets. When isolated and cultured, female VICs had higher levels of basal α-SMA stress fibers that further increased in response to the hydrogel matrix stiffness, both of which were higher than male VICs. A transcriptomic analysis of male and female porcine VICs revealed Rho-associated protein kinase (RhoA/ROCK) signaling as a potential driver of this sex-dependent myofibroblast activation. Further, we found that genes that escape X-chromosome inactivation, such as BMX and STS (encoding for Bmx non-receptor tyrosine kinase and steroid sulfatase, respectively) partially regulate the elevated female myofibroblast activation via RhoA/ROCK signaling. This finding was confirmed by treating male and female VICs with endothelin-1 and plasminogen activator inhibitor-1, factors that are secreted by endothelial cells and known to drive myofibroblast activation via RhoA/ROCK signaling. Together, in vivo and in vitro results confirm sex-dependencies in myofibroblast activation pathways, and transcriptome analyses and small molecule interventions implicate genes that escape X-chromosome inactivation in regulating sex differences in AVS progression. Our results underscore the importance of considering sex as a biological variable to understand the molecular mechanisms of AVS and help guide sex-based precision therapies.

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Many X-linked microRNAs escape meiotic sex chromosome inactivation.

Publications

Many X-linked microRNAs escape meiotic sex chromosome inactivation.

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