Objectives Fibroblast growth factor 9 (FGF9) is expressed by somatic cells in the seminiferous tubules, yet little information exists about its role in regulating spermatogonial stem cells (SSCs). Materials and Methods Fgf9 overexpression lentivirus was injected into mouse testes, and PLZF immunostaining was performed to investigate the effect of FGF9 on spermatogonia in vivo. Effect of FGF9 on SSCs was detected by transplanting cultured germ cells into tubules of testes. RNA‐seq of bulk RNA and single cell was performed to explore FGF9 working mechanisms. SB203580 was used to disrupt p38 MAPK pathway. p38 MAPK protein expression was detected by Western blot and qPCR was performed to determine different gene expression. Small interfering RNA (siRNA) was used to knock down Etv5 gene expression in germ cells. Results Overexpression of Fgf9 in vivo resulted in arrested spermatogenesis and accumulation of undifferentiated spermatogonia. Exposure of germ cell cultures to FGF9 resulted in larger numbers of SSCs over time. Inhibition of p38 MAPK phosphorylation negated the SSC growth advantage provided by FGF9. Etv5 and Bcl6b gene expressions were enhanced by FGF9 treatment. Gene knockdown of Etv5 disrupted the growth effect of FGF9 in cultured SSCs along with downstream expression of Bcl6b. Conclusions Taken together, these data indicate that FGF9 is an important regulator of SSC proliferation, operating through p38 MAPK phosphorylation and upregulating Etv5 and Bcl6b in turn.
Alternative splicing (AS) contributes to gene diversification, but the AS program during germline development remains largely undefined. Here, we interrupted pre-mRNA splicing events controlled by epithelial splicing regulatory protein 1 (ESRP1) and found that it induced female infertility in mice. Esrp1 deletion perturbed spindle organization, chromosome alignment and metaphase-to-anaphase transformation in oocytes. The first polar body extrusion was blocked during oocyte meiosis owing to abnormal activation of spindle assembly checkpoint and insufficiency of anaphase-promoting complex/cyclosome in Esrp1-knockout oocytes. Esrp1-knockout hampered follicular development and ovulation; eventually, premature ovarian failure occurred in six-month-old Esrp1-knockout mouse. Using single-cell RNA-seq analysis, 528 aberrant AS events of maternal mRNA transcripts were revealed and were preferentially associated with microtubule cytoskeletal organization. Notably, we found that loss of ESRP1 disturbed a comprehensive set of gene-splicing sites – including those within Trb53bp1, Rac1, Bora, Kif2c, Kif23, Ndel1, Kif3a, Cenpa and Lsm14b – that potentially caused abnormal spindle organization. Collectively, our findings provide the first report elucidating the ESRP1-mediated AS program of maternal mRNA transcripts, which may contribute to oocyte meiosis and female fertility in mice.
Alternative splicing (AS) contributes to gene diversification in cells, but the importance of AS during germline development remains largely undefined. Here, we interrupted premRNA splicing events controlled by epithelial splicing regulatory protein 1 (ESRP1) and found that it induced female infertility in mice. Germline-specific knockout of Esrp1 perturbed spindle organization, chromosome alignment, and metaphase-to-anaphase transformation in oocytes. The first polar body extrusion (PBE) was blocked during oocyte meiosis and was found to be due to abnormal activation of spindle assembly checkpoint (SAC) and insufficiency of anaphase-promoting complex/cyclosome (APC/C) in Esrp1-knockout oocytes. Esrp1-knockout in oocytes hampered follicular development and ovulation; eventually, premature ovarian failure (POF) occurred in six-month-old Esrp1-knockout mouse. Using single-cell RNA sequencing analysis, 528 aberrant AS events of maternal mRNA transcripts were revealed and were preferentially associated with microtubule cytoskeletal organization in Esrp1-knockout oocytes. Notably, we found that loss of ESRP1 disturbed a comprehensive set of gene-splicing sites-including those within Trb53bp1, Rac1, Bora, Kif2c, Kif23, Ndel1, Kif3a, Cenpa, and Lsm14b-that ultimately caused abnormal spindle organization. Taken together, our findings provide the first report elucidating the AS program of maternal mRNA transcripts, mediated by the splicing factor, ESRP1, that is required for oocyte meiosis and female fertility in mice.
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