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

Yongjuan Guan,Guanxiang Liang,Irek A Malecki,Greg Cozens,Philip E Vercoe,Penelope A R Hawken,Graeme B Martin,Le Luo Guan

doi:10.1038/srep10372

Abstract

We tested whether reductions in spermatozoal quality induced by under-nutrition are associated with increased germ cell apoptosis and disrupted spermatogenesis, and whether these effects are mediated by small RNAs. Groups of 8 male sheep were fed for a 10% increase or 10% decrease in body mass over 65 days. Underfeeding increased the number of apoptotic germ cells (P < 0.05) and increased the expression of apoptosis-related genes (P < 0.05) in testicular tissue. We identified 44 miRNAs and 35 putative piRNAs that were differentially expressed in well-fed and underfed males (FDR < 0.05). Some were related to reproductive system development, apoptosis (miRNAs), and sperm production and quality (piRNAs). Novel-miR-144 (miR-98), was found to 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 correlated (r = 0.8, P < 0.05) with the proportion of piRNAs in well-fed and underfed males. In conclusion, the reductions in spermatozoal quality induced by under-nutrition are caused, at least partly, by disruptions to Sertoli cell function and increased germ cell apoptosis, mediated by changes in the expression of miRNAs and piRNAs.

Highlights

Apoptosis in the testis – for example, suppression of FSH activity, which reduces Sertoli cell proliferation and germ cell number, leads to loss of germ cells through apoptosis rather than through a decrease in proliferation[11,12]
transferase mediated dUTP nick-end labeling (TUNEL)-positive germ cells were observed in all treatments (Fig. 1A,B), but most were seen in the early stages of spermatogenesis and none were seen amongst spermatids or spermatozoa
We identified 11 biological processes that were targeted within the category of development and function of the reproductive system, including apoptosis and Sertoli cell number (Fig. 4)

Summary

Introduction

Apoptosis in the testis – for example, suppression of FSH activity, which reduces Sertoli cell proliferation and germ cell number, leads to loss of germ cells through apoptosis rather than through a decrease in proliferation[11,12]. As important regulators of spermatogenesis and germ cell apoptosis, miRNAs and piRNAs should help explain the effects of nutrition on sperm production and sperm quality in males, for example, male sheep. We used sexually mature male sheep as a model because the reversible effects nutrition on testis mass, sperm production and sperm quality are well documented[28], providing a solid foundation for studying the roles of small RNAs. We 1) profiled miRNAs and piRNAs in sheep testis; 2) investigated the relationships among miRNA functions, spermatogenesis and germ cell apoptosis, during responses to nutrition; and 3) explored the potential for gene-derived piRNAs as regulators of spermatogenesis in the testis of the sexually mature sheep

Methods

Results

Conclusion