Characterization of COPII components in oocyte determination and maintenance in Drosophila melanogaster

Abstract

Oocyte fate determination and maintenance is a complicated process that depends on proper intracellular trafficking to establish anterior-posterior polarity in early oogenesis. However, the process of oocyte fate specification is still not fully understood in Drosophila melanogaster. Sec24CD mutant egg chambers exhibited loss of oocyte and ring canal clustering phenotypes, implicating the COPII pathway, an ER-to-Golgi secretory pathway, in playing a role in oocyte determination. It was discovered that the proper localization of Sec24CD is microtubule-dependent and accumulates posteriorly within the oocyte along with oocyte-specific markers. To further characterize the roles of other COPII components in oocyte polarity, Sec23 and Sar1 were investigated during Drosophila oogenesis. In this study, we show that Sec23 accumulates to the posterior cortex of the oocyte, colocalizing with three oocyte-specific factors, Orb, Bic-D, and Egl. Sec23 also colocalizes with Sec24CD and cis-Golgi marker GM130 to intracellular punctate. Additionally, proper Sec23 localization is microtubule-dependent. Furthermore, we discovered that RNAi knockdown of Sar1 exhibited phenotypes of loss of oocyte and ring canal clustering, similar to loss of Sec24CD. Our study provides evidence for the importance of COPII components in oocyte fate determination and maintenance, but specific roles of individual proteins during this process need to be further investigated. We suggest that a major step for future experiments will be to analyze potential interactions between COPII components and proteins involved in COPII vesicle transport or proteins that are essential for oocyte identity maintenance.