Abstract

It is well known thatcyclinB3(cycB3) plays a key role in the control of cell cycle progression. However, whethercycB3is involved in stem cell fate determination remains unknown. TheDrosophilaovary provides an exclusive model for studying the intrinsic and extrinsic factors that modulate the fate of germline stem cells (GSCs). Here, using this model, we show thatDrosophilacycB3plays a new role in controlling the fate of germline stem cells (GSC). Results fromcycB3genetic analyses demonstrate thatcycB3is intrinsically required for GSC maintenance. Results from green fluorescent protein (GFP)-transgene reporter assays show thatcycB3is not involved inDad-mediated regulation of Bmp signaling, or required fordpp-inducedbamtranscriptional silencing. Double mutants ofbamandcycB3phenocopiedbamsingle mutants, suggesting thatcycB3functions in abam-dependent manner in GSCs. Deficiency ofcycB3fails to cause apoptosis in GSCs or influence cystoblast (CB) differentiation into oocytes. Furthermore, overexpression ofcycB3dramatically increases the CB number inDrosophilaovaries, suggesting that an excess ofcycB3function delays CB differentiation. Given that thecycB3gene is evolutionarily conserved, from insects to humans,cycB3may also be involved in controlling the fate of GSCs in humans.Keywords:cyclinB3;germline stem cell;maintenance;overexpression;cystoblast;differentiation;Drosophila;ovary