148. HORMONAL REGULATION OF miRNA IN THE TESTIS

Abstract

Acute suppression of circulating reproductive hormones (FSH and testosterone) inhibits sperm release (spermiation) (1), although the molecular mechanisms of spermiation failure are poorly understood. Micro-RNAs (miRNAs) are small non-coding RNAs that regulate protein expression, and are essential for normal spermatogenesis. Recent studies suggest that miRNAs are exquisitely sensitive to hormonal control by FSH, LH and testosterone (2–4). This suggests that hormonal regulation of miRNAs in the testis following acute hormonal suppression may contribute to spermiation failure. Therefore, we hypothesised that gonadotrophin regulated miRNAs control spermiation outcome. We used array analysis to show that miRNA expression is hormonally regulated by FSH and testosterone in our rat in vivo model of spermiation failure and also in primary rat Sertoli cells by. qPCR validation revealed that miR-7b, -23a, -30c, -125b, -148b, -197, -483, -592, and -690 are all hormonally sensitive testicular miRNAs. Bioinformatic analyses of potential gene targets of these miRNAs predicted numerous protein components localised in the testicular tubulobulbar complex (TBC). The TBC is a podosome-like structure found between Sertoli cells and adjacent germ cells in the testis, and is thought to internalise intact inter-cellular structures and regulate spermatid head shape prior to spermiation. WASP, a TBC protein that regulates actin filament dynamics, contained a conserved binding site for miR-690 within its 3'UTR. Increased miR-690 expression following hormone suppression corresponded to a decrease in WASP protein expression in vivo and in vitro. In addition, transfection of miR-690 into HEK293T cells down-regulated WASP protein. Our results suggest that following hormone suppression, miR-690 is stimulated in the Sertoli cell, thereby inhibiting WASP protein expression. We conclude that miRNA-mediated disruption of TBC integrity potentially regulates spermatid disengagement. This study describes new molecular mechanisms in the testis that may control spermiation outcome of potential significance in male hormonal contraception.