Dynamic RNP aggregates in C. elegans oocytes
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Overview
Overview
Description
As C. elegans hermaphrodites age, sperm become depleted, oogenesis arrests, and oocytes accumulate in the gonad arm. Giant ribonucleoprotein (RNP) aggregates form in these arrested oocytes that contain putative RNA binding proteins and translationally masked maternal mRNAs. Within 2 h after mating and replenishing the hermaphrodite’s supply of sperm, the RNP aggregates dissociate and fertilization proceeds. The majority of arrested oocytes with aggregates result in viable embryos upon fertilization, suggesting that aggregates are not deleterious to oocyte function. We have determined that aggregate formation is not strictly a function of aging, as RNP aggregates form in arrested oocytes of several mutants that are not old-aged but either lack normal sperm or have arrested oogenesis. They also reversibly form in the oocytes of unmated C. remanei females and therefore this dynamic phenomenon appears to be conserved. One attractive hypothesis is that the RNA-binding proteins in aggregates protect maternal mRNA from either degradation or precocious translation while the oocytes wait an extended period to be fertilized. We have preliminarily identified a mutant that does not form RNP aggregates when oogenesis is arrested. Interestingly, the majority of these arrested ooctyes do not give rise to viable embryos after fertilization. Thus, an intriguing correlation exists between the ability to form RNP aggregates when oogenesis is arrested and the ability to preserve ooctye integrity such that embryonic viability is assured.
