Membrane-associated cytoplasmic granules carrying the Argonaute protein WAGO-3 enable paternal epigenetic inheritance in Caenorhabditis elegans

Abstract

Transgenerational epigenetic inheritance (TEI) describes the transmission of gene-regulatory information across generations without altering DNA sequences, and allows priming of offspring towards transposable elements (TEs) and changing environmental conditions. One important mechanism that acts in TEI is based on small non-coding RNAs. Whereas factors for maternal inheritance of small RNAs have been identified, paternal inheritance is poorly understood, as much of the cellular content is extruded during spermatogenesis. We identify a phase separation-based mechanism, driven by the protein PEI-1, which is characterized by a BTB-BACK domain and an intrinsically disordered region (IDR). PEI-1 specifically secures the Argonaute protein WAGO-3 within maturing sperm in C. elegans. Localization of PEI granules in mature sperm is coupled, via Spalmitoylation, to myosin-driven transport of membranous organelles. pei-1-like genes are also found in human and often expressed in testis, suggesting that the here identified mechanism may be broadly conserved.

A comprehensive survey of C. elegans argonaute proteins reveals organism-wide gene regulatory networks and functions

“…Both 3xFLAG tagged AGOs were functional in phenotypic assays ( Figure 1C and H ). We note that although PPW-2 (also known as WAGO-3) and WAGO-1 were recently shown to be N-terminally processed by the protease DPF-1, both GFP::3xFLAG::PPW-2 and 3xFLAG::WAGO-1 strains behaved as wild-type, consistent with previous reports ( Gudipati et al, 2021 ; Schreier et al, 2022 ). The tagged C04F12.1/VSRA-1 and WAGO-10 were not tested for a specific phenotype as there are no known phenotypes for C04F12.1/vsra-1 and wago-10 mutants.…”

A Comprehensive Survey of C. elegans Argonaute Proteins Reveals Organism-wide Gene Regulatory Networks and Functions

“…This temperature-dependent fertility defect can manifest in the first generation subsequent to a temperature shift or take several generations to reach its full impact. Several germ granule component mutants and ago mutants, including hrde-1 , prg-1 , wago-4 , and ppw-2 have been shown to exhibit a Mortal germline (Mrt) phenotype, in which fertility decreases over several generations at elevated temperature (Buckley et al ., 2012; Simon et al ., 2014; Wan et al ., 2018; Schreier et al ., 2022). We therefore performed brood size assays at 20°C and 25°C for recently outcrossed hermaphrodites of each single ago mutant (Fig 6D).…”

“…ALG-3, ALG-4, WAGO-10, and the CSR-1a isoform are expressed only during spermatogenesis, at the L4 stage in hermaphrodites and constitutively in the male germline (Charlesworth et al ., 2021; Nguyen and Phillips, 2021)(Fig 6A and Fig S12). Only PPW-2 and CSR-1b are detectable in spermatids (Fig 6A) (Charlesworth et al ., 2021; Schreier et al ., 2022). ALG-2, ERGO-1, and NRDE-3 are specifically expressed in oocytes starting at the young adult hermaphrodite stage (Fig 6A).…”

Where are all the egg genes?

“…How are all the sperm and egg components assembled into complexes and at the right time and place? Genes are being discovered that may impact the processing and assembly of the fertilization synapse (Gleason et al, 2006;Contreras et al, 2022;Schreier et al, OPEN ACCESS EDITED BY Shao-Chen Sun, Nanjing Agricultural University, China 2022). For example, Frey can regulate the assembly of Izumo1, a key protein involved in fertilization on the surface of the sperm (Contreras et al, 2022).…”