ReviewSmall non-coding RNAs and their associated proteins in spermatogenesis

•Three kinds of small RNAs appear to be involved in spermatogenesis.•Many miRNA species are involved in germ cell development of male animals.•piRNAs and PIWI proteins are closely related to spermatogenesis.•Endo-siRNAs maybe also regulate male germ cell development.•The male germ granules appear to affect small RNA regulation and spermatogenesis.

The importance of the gene regulation roles of small non-coding RNAs and their protein partners is of increasing focus. In this paper, we reviewed three main small RNA species which appear to affect spermatogenesis. MicroRNAs (miRNAs) are single stand RNAs derived from transcripts containing stem-loops and hairpins which target corresponding mRNAs and affect their stability or translation. Many miRNA species have been found to be related to normal male germ cell development. The biogenesis of piRNAs is still largely unknown but several models have been proposed. Some piRNAs and PIWIs target transposable elements and it is these that may be active in regulating translation or stem cell maintenance. endo-siRNAs may also participate in sperm development. Some possible interactions between different kinds of small RNAs have even been suggested. We also show that male germ granules are seen to have a close relationship with a considerable number of mRNAs and small RNAs. Those special structures may also participate in sperm development.