Germ granule-mediated RNA regulation in male germ cells.

Germ cells have exceptionally diverse transcriptomes. Furthermore, the progress of spermatogenesis is accompanied by dramatic changes in gene expression patterns, the most drastic of them being near-to-complete transcriptional silencing during the final steps of differentiation. Therefore, accurate RNA regulatory mechanisms are critical for normal spermatogenesis. Cytoplasmic germ cell-specific ribonucleoprotein (RNP) granules, known as germ granules, participate in posttranscriptional regulation in developing male germ cells. Particularly, germ granules provide platforms for the PIWI-interacting RNA (piRNA) pathway and appear to be involved both in piRNA biogenesis and piRNA-targeted RNA degradation. Recently, other RNA regulatory mechanisms, such as the nonsense-mediated mRNA decay pathway have also been associated to germ granules providing new exciting insights into the function of germ granules. In this review article, we will summarize our current knowledge on the role of germ granules in the control of mammalian male germ cell's transcriptome and in the maintenance of fertility.