An isoform of eIF4E is a component of germ granules and is required for spermatogenesis in C-elegans

Control of gene expression at the translational level is crucial for many d evelopmental processes. The mRNA cap-binding protein, eIF4E, is a key playe r in regulation of translation initiation; appropriate levels of eIF4E are essential for normal cell-cycle regulation and tissue differentiation. The observation that eIF4E levels are elevated during gametogenesis in several organisms suggests that eIF4E might have a specific role in gamete formatio n as well. We show that one of the five isoforms of C. elegans eIF4E, IFE-1 , is enriched in the germline and is a component of germ granules (P granul es). The association of IFE-1 with P granules requires the P-granule protei n PGL-1. In vitro PGL-1 interacts directly with IFE-1, but not with the oth er four isoforms of eIF4E. Analysis of animals depleted of IFE-1 by RNAi sh ows that IFE-1 is required for spermatogenesis, specifically for efficient progression through the meiotic divisions and for the production of functio nal sperm, in both hermaphrodites and males. The requirement for IFE-1 is h ighly sensitive to temperature. IFE-1 is not required for oogenesis, as ife -1(RNAi) hermaphrodites produce viable progeny when normal sperm are suppli ed. Consistent with a primary role in spermatogenesis, ife-1 m-RNA levels a re highest in regions of the gonad undergoing spermatogenesis. Our results suggest that C. elegans spermatogenesis requires either this specific isofo rm. of eIF4E or an elevated level of eIF4E.