The mouse Balbiani body regulates primary oocyte quiescence via RNA storage

In mammalian females, the transition between dormancy in primordial follicles and follicular development is critical for maintaining ovarian function and reproductive longevity. In mice, the quiescent primary oocyte of the primordial follicle contains a Balbiani body (B-body), represented by a spherical aggregate of Golgi complexes. Here we show that the structure of the B-body is maintained by microtubules and actin. The B-body stores mRNA-capping enzyme and 597 mRNAs associated with mRNA-decapping enzyme 1A (DCP1A). Gene ontology analysis results indicate that proteins encoded by these mRNAs function in enzyme binding, cellular component organization and packing of telomere ends. Pharmacological depolymerize microtubules or actin led to B-body disassociation and nascent protein synthesis around the dissociated B-bodies within three hours. An increased number of activated developing follicles were observed in ovaries with prolonged culture and in vivo mouse model. Our results indicate that the mouse B-body is involved in the activation of dormant primordial follicles likely via translation of the B-body-stored RNAs in primary oocytes. To identify the RNAs that interact with DCP1A protein in mouse primary oocytes, we conducted RNA-immunoprecipitation sequencing of postnatal day 8 ovarian cortex tissues using a DCP1A antibody.