Mutations inCog7affect Golgi structure, meiotic cytokinesis and sperm development duringDrosophilaspermatogenesis

Abstract

The conserved oligomeric Golgi (COG) Complex plays essential roles for Golgi function, vesicle trafficking and glycosylation. Deletions of human COG7 are associated with a rare multisystemic congenital disorder of glycosylation causing mortality within the first year of life. Here we characterize the Drosophila ortholog of COG7 (Cog7). Loss-of-function Cog7 mutants are viable but male sterile. Cog7 is enriched in both the Golgi stacks and the Golgi derived structures throughout spermatogenesis. Mutations in Cog7 disrupt Golgi architecture and reduce the number of Golgi stacks in primary spermatocytes. During spermiogenesis, loss of Cog7 impairs the assembly of the Golgi-derived acroblast in spermatids and affects axoneme architecture. Similarly to the Cog5 homologue Four way stop (Fws), Cog7 enables furrow ingression during cytokinesis. We show that the recruitment of both the small GTPase Rab11 and the phosphatidylinositol transfer protein Giotto (Gio) to the cleavage site requires the wild type function of Cog7. In addition Gio coimmunoprecipitates with both Cog7 and Rab11 in testes. Together our results implicate Cog7 as an upstream component in a gio-Rab11 pathway controlling membrane addition during cytokinesis.