ELLI-1,a novel germline protein,modulates RNAi activity and P-granule accumulation in Caenorhabditis elegans

Germ cells contain non-membrane bound cytoplasmic organelles that help maintain germline integrity. in c. elegans they are called p granules; without them,the germline undergoes partial masculinization and aberrant differentiation. one key p-granule component is the argonaute csr-1,a small-rna binding protein that antagonizes accumulation of sperm-specific transcripts in developing oocytes and fine-tunes expression of proteins critical to early embryogenesis. loss of csr-1 complex components results in a very specific,enlarged p-granule phenotype. in a forward screen to identify mutants with abnormal p granules,ten alleles were recovered with a csr-1 p-granule phenotype,eight of which contain mutations in known components of the csr-1 complex (csr-1,ego-1,ekl-1,and drh-3). the remaining two alleles are in a novel gene now called elli-1 (enlarged germline granules). elli-1 is first expressed in primordial germ cells during mid-embryogenesis,and continues to be expressed in the adult germline. while elli-1 forms cytoplasmic aggregates,they occasionally dock,but do not co-localize with p granules. instead,the majority of elli-1 aggregates accumulate in the shared germline cytoplasm. in elli-1 mutants,several genes that promote rnai and p-granule accumulation are upregulated,and embryonic lethality,sterility,and rnai resistance in a hypomorphic drh-3 allele is enhanced,suggesting that elli-1 functions with csr-1 to modulate rnai activity,p-granule accumulation,and post-transcriptional expression in the germline. © 2017 andralojc et al.