microRNA 376a regulates follicle assembly by targeting Pcna in fetal and neonatal mouse ovaries

Abstract

In mammals, the primordial follicle pool, providing all oocytes available to a female throughout her reproductive life, is established perinatally. Dysregulation of primordial follicle assembly results in female reproductive diseases, such as premature ovarian insufficiency and infertility. Female mice lacking Dicer1 (Dicer), a gene required for biogenesis of microRNAs, show abnormal morphology of follicles and infertility. However, the contribution of individual microRNAs to primordial follicle assembly remains largely unknown. Here, we report that microRNA 376a (miR-376a) regulates primordial follicle assembly by modulating the expression of proliferating cell nuclear antigen (Pcna), a gene we previously reported to regulate primordial follicle assembly by regulating oocyte apoptosis in mouse ovaries. miR-376a was shown to be negatively correlated with Pcna mRNA expression in fetal and neonatal mouse ovaries and to directly bind to Pcna mRNA 3 0 untranslated region. Cultured 18.5 days postcoitum mouse ovaries transfected with miR-376a exhibited decreased Pcna expression both in protein and mRNA levels. Moreover, miR-376a overexpression significantly increased primordial follicles and reduced apoptosis of oocytes, which was very similar to those in ovaries co-transfected with miR-376a and siRNAs targeting Pcna. Taken together, our results demonstrate that miR-376a regulates primordial follicle assembly by modulating the expression of Pcna. To our knowledge, this is the first microRNA-target mRNA pair that has been reported to regulate mammalian primordial follicle assembly and further our understanding of the regulation of primordial follicle assembly.

Multifaceted programmed cell death in the mammalian fetal ovary

“…In any case, PCNA-mediated oocyte apoptosis depends on the availability of the inhibitor of growth 1 (ING1), a member of an evolutionarily conserved family of tumor suppressor proteins, and results in increasing Bax, casp-3 and Par6 and decreasing Bcl-2 gene expression (Xu et al, 2011). Interestingly, the oocytes were protected from the PCNA dependent apoptosis by the micro RNA 376a that, by directly binding to the 3' untraslated region (UTR) of the PCNA mRNA, inhibits its translation (Zhang et al, 2014).…”

MicroRNAs: tiny molecules with a significant role in mammalian follicular and oocyte development

“…The female fertility of mammalian species is a dynamic and well-coordinated process miR-376a in neonatal mouse primordial follicles was reported by Zhang et al (2014).…”

A Role of MicroRNAs in Cell Differentiation During Gonad Development

“…In another study conducted by the same group, miR-376a was found to downregulate PCNA expression and its expression was reciprocally correlated with that of PCNA mRNA in fetal mouse ovaries. Furthermore, cultured 18.5 dpc ovaries transfected with miR-376a exhibited reduced apoptosis of oocytes and an increase in the number of primordial follicles; this effect was mediated by miR-376a-inhibition of PCNA (Zhang et al 2014a). These findings imply that by inhibiting oocytes' apoptosis miR-376a acts as a positive regulator of primordial follicles assembly.…”