Regulation of exclusively testis‐expressed microRNA‐469 by Gonadotropin‐Regulated Testicular RNA Helicase controls male germ cells development

Abstract

Gonadotropin‐regulated testicular RNA helicase (GRTH/DDX25), a testis‐specific member of the DEAD‐box family, is an essential post‐transcriptional regulator of spermatogenesis. Failure of expression of Transition protein 2 (TP2) and Protamine 2 (Prm2) proteins (chromatin remodelers, essential for spermatid elongation and completion of spermatogenesis) with preservation of their mRNAs expression was observed in GRTH−/− mice (azoospermic due to failure of spermatids to elongate). These were identified as target genes for the testis‐specific miR‐469, which is increased in the GRTH−/− mice. Further analysis demonstrated that miR‐469 repressed TP2 and Prm2 protein expression at the translation level with minor effect on mRNA degradation, through binding to the coding regions of TP2 and Prm2 mRNAs. The corresponding primary‐miRNAs and the expression levels of Drosha and DGCR8 (mRNA and protein) were increased significantly in the GRTH−/− mice. miR‐469 silencing of TP2 and Prm2 mRNA in pachytene spermatocytes and round spermatids is essential for their timely translation at later times of spermiogenesis which is critical to attain mature sperm. Collectively, these studies indicate that GRTH, a multifunctional RNA helicase, acts as a negative regulator of miRNA biogenesis and consequently their function during spermatogenesis. (Supported by the IRP, NICHD)