A role for cappuccino and chickadee in regulation of vesicle transport during Drosophila development

• Main Author: Balasundaram, Sujatha
• Other Authors: Ramaswami, Mani
• Language: EN
• Published: The University of Arizona. 2006
• Subjects: Formin; cappuccino; spire; chickadee; endocytosis; yolk
• Online Access: http://hdl.handle.net/10150/193754

Establishment of polarity is a critical process that occurs early during development. In Drosophila melanogaster, axis determination occurs by localization of determinants during oogenesis. Mutations in cappuccino (capu) lead to defects in polarity establishment of both the anterior/posterior (A/P) and dorsal/ventral (D/V) axes during oogenesis. In the oocytes laid by capu mutant females, determinants that define these axes are either mislocalized or are absent. Several lines of evidence suggest that the regulation of cytoskeleton by the gene product encoded by capu is involved in Drosophila oogenesis.Capu, a member of the formin family of proteins, known to be regulators of actin dynamics, interacts both genetically and physically with chickadee (chic) which encodes the actin binding protein Profilin. I show here that mutations in both capu and chic lead to defects in the endocytic uptake of yolk into developing oocytes. I show that mutations in these loci lead to accumulation of abnormally large yolk granules and that this is a post internalization defect in the oocyte of capu and chic females. I also present evidence which indicates that an interaction with capu is necessary for chic regulation of yolk granule biogenesis.This is the first evidence for a formin subfamily of formin proteins to have a role in endocytosis. While this new function identified for the actin associated proteins Capu and Profilin indicates that regulation of actin cytoskeleton plays a role in endocytosis during oogenesis, the mechanism of this regulation and possible actin independent roles played by Capu and Profilin in this process are yet to be determined.Like capu, mutations in spire (spir) also show defects in A/P and D/V axes during oogenesis. Spir is an actin binding protein and like capu, mutations in spir shows defects in cytoskeletal architecture and suggests that capu and spire alter microtubule distribution in the oocyte during oogenesis.To identify molecular partners of capu and spir and their roles during oogenesis, I performed a genome-wide deficiency screen to identify regions of the genome that interact with these genes. I identified regions in the genome that showed interaction with capu and spir. While I was able to narrow down the region of interaction to a smaller cytological interval, gaps in the deficiency coverage and lack of mutants in those regions prevented me from identifying interacting loci in those regions.