Spatial and temporal translational control of germ cell mRNAs via an eIF4E isoform, IFE-1.

Regulated mRNA translation is vital for germ cells to produce new proteins in the spatial and temporal patterns that drive gamete development. Translational control involves the de-repression of stored mRNAs and their recruitment by initiation factors (eIF's) to ribosomes. C. elegans expresses five eIF4Es (IFE-1-5); several were shown to selectively recruit unique pools of mRNA. Individual IFE knockouts yield unique phenotypes due to inefficient translation of certain mRNAs. We identified mRNAs preferentially translated via a germline-specific eIF4E isoform, IFE-1. Differential polysome microarray analysis identified 77 mRNAs recruited by IFE-1. Among the IFE-1-dependent mRNAs are several required for late germ cell differentiation and maturation. Polysome association of gld-1, vab-1, vpr-1, rab-7, and rnp-3 mRNAs relies on IFE-1. Live animal imaging showed IFE-1-dependent selectivity in spatial and temporal translation of germline mRNAs. Altered MAPK activation in oocytes suggests dual roles for IFE-1, both promoting and suppressing oocyte maturation at different stages. This single eIF4E isoform exerts positive, selective translational control during germ cell differentiation.