Roles of small RNAs in the effects of nutrition on apoptosis and spermatogenesis in the adult testis

In this study, we tested whether reduction in spermatozoal quality induced by under-nutrition is associated with an increase in germ cell apoptosis and a reduction in spermatogenesis, and whether these effects are regulated by small RNAs. Groups of 8 male sheep were fed for a 10% increase or 10% decrease in body mass over 65 days. Testicular tissue from underfed males had more apoptotic germ cells (TUNEL assay; P < 0.05) and greater (P < 0.05) levels of expression of apoptosis-related genes than well-fed males. We identified 44 miRNAs and 35 piRNAs that were differentially expressed in well-fed and underfed males (FDR < 0.05) and found that they were predominantly related to development of the reproductive system, apoptosis (miRNAs), or sperm production and quality (piRNAs). Furthermore, experimental validation showed that novel-miR-144, a homologue of miR-98, would target three apoptotic genes (TP53, CASP3, FASL). The proportion of miRNAs as a total of small RNAs was greater in well-fed males than in underfed males (P < 0.05) and was positively correlated with the proportion of piRNAs in well-fed males (r = 0.8, P < 0.05) and underfed males (r = 0.8, P < 0.05). We conclude that the reductions in spermatozoal quality induced by under-nutrition are due, at least partly, to increased germ cell apoptosis and to changes in the expression of miRNAs and piRNAs. Overall design: Two groups of 8 male sheep were fed for a 10% increase or 10% decrease in body mass over 65 days, and the small RNA expression was profiled.