RNA-binding proteins, RNA granules, and gametes: is unity strength?

Abstract

Changes in mRNA translation and degradation represent post-transcriptional processes operating during gametogenesis and early embryogenesis to ensure regulated protein synthesis. Numerous mRNA-binding proteins (RBPs) have been described in multiple animal models that contribute to the control of mRNA translation and decay during oogenesis and spermatogenesis. An emerging view from studies performed in germ cells and somatic cells is that RBPs associate with their target mRNAs in RNA-protein (or ribonucleoprotein) complexes (mRNPs) that assemble in various cytoplasmic RNA granules that communicate with the translation machinery and control mRNA storage, triage, and degradation. In comparison with Xenopus, Caenorhabditis elegans, or Drosophila, the composition and role of cytoplasmic RNA-containing granules in mammalian germ cells are still poorly understood. However, regained interest for these structures has emerged with the recent discovery of their role in small RNA synthesis and transposon silencing through DNA methylation. In this review, we will briefly summarize our current knowledge on cytoplasmic RNA granules in murine germ cells and describe the role of some of the RBPs they contain in regulating mRNA metabolism and small RNA processing during gametogenesis.

piRNAs-Transposon Silencing and Germ Line Development

“…Like in Drosophila , the integrity of P-bodies depends on the expression of TDRD and other proteins. Miwi is present in the whole of the cytoplasm in spermatocytes, and it concentrates in the chromatoid bodies in the round spermatids [ 81 ]. Mili and/or Miwi mutations, in combination with defi ciencies in specifi c TDRDs, cause reductions in piRNA levels in mouse male germ cells, and increase retrotransposon transcription (LINE and LTR).…”

GDNF Signaling Regulates YBX1/mRNA Interactions in Mouse Spermatogonia.

“…We chose to focus on fourteen of the RNA binding protein encoding genes identified in the microarray, which are listed in Table 2. The genes vary in RNA regulatory function, and some serve multiple functions, probably due to the pleiotropic activities of RNA binding proteins and their regulatory centers [126,179,180]. The most common functions of these 14 genes are splicing and translational control.…”

Germline deletion of huntingtin causes male infertility and arrested spermiogenesis in mice

“…While in spermiogenesis, round spermatids pass through 16 stages to differentiate into spermatozoa, which have specialized organelles for motility and fertilization (Oakberg, 1956). During spermatogenesis, translational regulation plays an important role in the development of spermatocytes and spermatids (Paronetto and Sette, 2010;Nguyen-Chi and Morello, 2011;Idler and Yan, 2012;Kleene, 2013). Many mRNA transcribed in spermatocytes and round spermatids are stored in a translationally inactive state for several days to more than two weeks, before their protein products can be detected in elongating and elongated spermatids.…”