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. Thus, unlike X-chromosome inactivation in female embryonic or somatic cells, where 25-30% of X-linked structural genes have been reported to escape inactivation, there have been no previous reports of genes that escape the silencing effects of MSCI in primary spermatocytes. However, we recently discovered that many X-linked microRNAs (miRNAs) are transcribed and processed in pachytene spermatocytes. This unprecedented escape from MSCI suggests that these miRNAs participate in one or more critical functions at this stage of spermatogenesis. This is corroborated by our preliminary finding that chimeric mice carrying a high percentage of cells bearing a knockout of a major cluster of X-linked miRNA genes display a fertility defect manifest as a block during the meiotic phase of spermatogenesis. This is significant because despite recent reports describing expression of an abundance of miRNAs and other small, non-coding RNAs during spermatogenesis, essentially nothing is known about the function of any of these. In this application, we first propose to investigate the molecular mechanism by which these X-linked miRNA genes escape MSCI (Aim 1). We then propose to test two hypotheses (which are not mutually exclusive) regarding function of these miRNAs, including their role as post- transcriptional regulators of autosomal mRNAs that are synthesized during meiosis but not translated until the postmeiotic period (Aim 2), and their role in regulating the process of MSCI itself (Aim 3). This study is highly novel in that it is designed to reveal an unprecedented mechanism of escape from MSCI, and to identify actual functions of those X-linked miRNAs that undergo this escape during spermatogenesis.

Public Health Relevance

Understanding the molecular and genetic mechanisms by which sperm are produced is critically important for diagnosis and treatment of male infertility, as well as for the development of non-hormonal male-specific contraceptives. Data from the present study will contribute insight into the function of X-linked miRNAs in the control of sperm production and male fertility.

National Institute of Health (NIH)
Research Project (R01)
Project #
Application #
Study Section
Cellular, Molecular and Integrative Reproduction Study Section (CMIR)
Program Officer
Moss, Stuart B
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Nevada Reno
Schools of Medicine
United States
Zip Code
Wu, Jingwen; Bao, Jianqiang; Kim, Minkyung et al. (2014) Two miRNA clusters, miR-34b/c and miR-449, are essential for normal brain development, motile ciliogenesis, and spermatogenesis. Proc Natl Acad Sci U S A 111:E2851-7
Bao, J; Zhang, Y; Schuster, A S et al. (2014) Conditional inactivation of Miwi2 reveals that MIWI2 is only essential for prospermatogonial development in mice. Cell Death Differ 21:783-96
Yuan, Shuiqiao; Ortogero, Nicole; Wu, Qiuxia et al. (2014) Murine follicular development requires oocyte DICER, but not DROSHA. Biol Reprod 91:39
Yan, Wei (2014) Potential roles of noncoding RNAs in environmental epigenetic transgenerational inheritance. Mol Cell Endocrinol 398:24-30
Bao, Jianqiang; Yuan, Shuiqiao; Maestas, Ashley et al. (2013) Stk31 is dispensable for embryonic development and spermatogenesis in mice. Mol Reprod Dev 80:786
Bao, Jianqiang; Ma, Hsiu-Yen; Schuster, Andrew et al. (2013) Incomplete cre-mediated excision leads to phenotypic differences between Stra8-iCre; Mov10l1(lox/lox) and Stra8-iCre; Mov10l1(lox/?) mice. Genesis 51:481-90
Ro, Seungil; Ma, Hsiu-Yen; Park, Chanjae et al. (2013) The mitochondrial genome encodes abundant small noncoding RNAs. Cell Res 23:759-74
Bao, Jianqiang; Wu, Jingwen; Schuster, Andrew S et al. (2013) Expression profiling reveals developmentally regulated lncRNA repertoire in the mouse male germline. Biol Reprod 89:107
Ortogero, Nicole; Hennig, Grant W; Langille, Chad et al. (2013) Computer-assisted annotation of murine Sertoli cell small RNA transcriptome. Biol Reprod 88:3
Bao, Jianqiang; Yan, Wei (2012) Male germline control of transposable elements. Biol Reprod 86:162, 1-14

Showing the most recent 10 out of 14 publications