Follicle-stimulating hormone-mediated decline in miR-92a-3p expression in pubertal mice Sertoli cells is crucial for germ cell differentiation and fertility.

Sertoli cells (Sc) are the sole target of follicle-stimulating hormone (FSH) in the testis and attain functional maturation post-birth to significantly augment germ cell (Gc) division and differentiation at puberty. Despite having an operational microRNA (miRNA) machinery, limited information is available on miRNA-mediated regulation of Sc maturation and male fertility. We have shown before that miR-92a-3p levels decline in pubertal rat Sc. In response to FSH treatment, the expressions of FSH Receptor, Claudin11 and Klf4 were found to be elevated in pubertal rat Sc coinciding with our finding of FSH-induced decline in miR-92a-3p levels. To investigate the association of miR-92a-3p and spermatogenesis, we generated transgenic mice where such pubertal decline of miR-92a-3p was prevented by its overexpression in pubertal Sc under proximal Rhox5 promoter, which is known to be activated specifically at puberty, in Sc. Our in vivo observations provided substantial evidence that FSH-induced decline in miR-92a-3p expression during Sc maturation acts as an essential prerequisite for the pubertal onset of spermatogenesis. Elevated expression of miR-92a-3p in post-pubertal testes results into functionally compromised Sc, leading to impairment of the blood-testis barrier formation and apoptosis of pre-meiotic Gc, ultimately culminating into infertility. Collectively, our data suggest that regulation of miR-92a-3p expression is crucial for Sc-mediated induction of active spermatogenesis at puberty and regulation of male fertility.

Regulation of Hippo pathway components by FSH in testis.

The transition of testicular Sertoli cells (Sc) from a proliferative state during infancy to a non proliferative functionally mature state at the onset of puberty is essential for proper spermatogenic progression. The Hippo signaling pathway is a conserved growth control pathway that has been shown to play a crucial role in regulating proliferation and differentiation of different cell types. However, the expression pattern of the pathway components relative to proliferative infant Sc and functionally mature pubertal Sc is not known. In this study, we show that the Hippo pathway components are differentially expressed in infant and pubertal rat Sc. Interestingly, Hippo transducer- YAP was found to be significantly up-regulated in pubertal Sc as compared to infant Sc. Follicle stimulating hormone (FSH) was found to up-regulate Yap expression in pubertal Sc but not in infant Sc. Moreover, FSH induced the phosphorylation of YAP at Ser 127 residue (which is associated with its inactivation) in pubertal Sc. This indicated negative regulation of YAP by FSH mediated signaling in pubertal Sc. Our results demonstrated the differential expression of Hippo pathway genes in infant and pubertal Sc and also established an important role of FSH in regulating YAP expression and phosphorylation in Sc.