Analysis of RNA associated with P granules in germ cells of C. elegans adults

Abstract

P granules are cytoplasmic structures of unknown function that are associated with germ nuclei in the C. elegans gonad, and are localized exclusively to germ cells, or germ cell precursors, throughout the life cycle. All the known protein components of P granules contain putative RNA-binding motifs, suggesting that RNA is involved in either the structure or function of the granules. However, no specific mRNAs have been identified within P granules in the gonad. We show here that P granules normally contain a low level of RNA, and describe conditions that increase this level. We present evidence that several, diverse mRNAs, including pos-1, mex-1, par-3, skn-1, nos-2 and gld-1 mRNA, are present at least transiently within P granules. In contrast, actin and tubulin mRNA and rRNA are either not present in P granules, or are present at relatively low levels. We show that pgl-1 and the glh (Vasa-related) gene family, which encode protein components of P granules, do not appear essential for RNA to concentrate in P granules; these proteins may instead function in events that are a prerequisite for RNAs to be transported efficiently from the nuclear surface.

RNA length has a non-trivial effect in the stability of biomolecular condensates formed by RNA-binding proteins

“…Beyond compartmentalization, numerous vital roles have been recently associated with biomolecular condensates, including cell signaling [2,7], formation of super-enhancers [8], genome organization [9][10][11][12], and aiding cells to sense and react to environmental changes [13] among many others [14][15][16][17]. Within the extensive class of biomolecules that can undergo phase separation at physiological conditions, RNA-binding proteins (RBPs) such as FUS [18][19][20], hnRNPA1 [21,22], TDP-43 [23][24][25], TAF-15 [26,27], G3BP1 [28][29][30][31] or EWSR1 [26,27,32], have been widely investigated due to their implications in the stability of stress granules [33,34], P granules [1,35,36] or RNA granules/bodies [37][38][39]important phase-separated organelles within cells.…”

Formation of mos RNA granules in the zebrafish oocyte that differ from cyclin B1 RNA granules in distribution, density and regulation

“…In nematodes, several types of RNA granules have been observed in the cytoplasm of different stages of oocytes. Caenorhabditis elegans oocytes form germ granules and processing body (P body)-like granules, which are compositionally different and contain different sets of dormant mRNAs (Boag et al, 2008;Noble et al, 2008;Schisa et al, 2001). In contrast to nematode oocytes, only a few granules containing mRNAs have been observed in vertebrate oocytes.…”

Expansion microscopy reveals subdomains in C. elegans germ granules

“…In this regard, the P granule presents particular challenges in understanding how LLPS facilitates its functions due to the complexity in its composition: more than 40 proteins have been identified as associated with this organelle (Suen et al, 2020; Sundby et al, 2021; Updike and Strome, 2010) and most RNAs in the germline are thought to at least associate with it transiently (Schisa et al, 2001; Sheth et al, 2010). Whilst certain proteins, e.g.…”