The P granules are the C. elegans germ granules, RNA granules specific to the germline. In the embryo, P granules segregate asymmetrically with the P lineage for inheritance by the primordial germ cells (PGCs) Z2 and Z3. P granules are thought to regulate RNAs with critical germline functions, such as the Nanos homolog nos-2, but the function and structure of embryonic P granules are not well understood. We previously reported that embryonic P granules are heterogeneous organelles consisting of an inner core and an outer scaffold (Wang et al., 2014). The inner core contains the PGL and GLH class of RNA-binding proteins that are found in P granules throughout development. The outer scaffold contains a novel class of intrinsically-disordered and serine-rich proteins (MEGs) that associate with P granules only in embryos.
Surprisingly, our genetic analyses suggest that the MEG proteins mediate the essential function of P granules in embryos independently of the PGL/GLH cores. Embryos lacking the MEGs do not assemble PGL/GLH granules, do not express NOS-2 (or express very low levels), exhibit PGC defects characteristic of embryos lacking Nanos activity, and are sterile. In contrast, embryos that do not form PGL/GLH granules still form RNA-positive MEG granules, express NOS-2, and are fertile. We conclude that the intrinsically-disordered MEGs mediate the essential functions of P granules during embryogenesis. We speculate that the MEGs may be functional homologues of other intrinsically disordered proteins that scaffold RNA granules in germ cells, such as vertebrate Bucky ball. .
Please note: Abstract shown here should NOT be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
The Genetics Society of America
9650 Rockville Pike, Bethesda, MD
Phone: 301-634-7300, Fax: 301-634-7079
Questions and Comments: firstname.lastname@example.org