Functional Analysis of Rab7 in Drosophila Border Cells

Abstract

Cell polarization plays a critical role in animal development which is not only involved in cell fate determination morphogenesis but also in progression of cancer particularly in metastasis Asymmetry localization of polarity proteins define apical-basal polarity set up boundary for junctional proteins and polarize vesicle trafficking route in epithelial cells But the mechanism by which the cell polarity changes in the transition from a stable epithelium to motile cells during morphogenesis remains largely unknown In this study we use border cells (BCs) originated from epithelial cells that would transform to a motile cluster in D melanogaster oogenesis as a model to study the distribution of polarity protein during migration Before detachment border cells still preserved apical-basal polarity but the expression of basolateral markers Scribble and Disc large gradually reduced once border cells start to migrate We further investigate and found that the Rab family protein Rab7 participated in regulation of polarity proteins In the rab7 mutant cells we observed the apical marker Crumbs and adhesion junction proteins E-cadherin and Armadillo extending toward the basolateral side which in turn caused migration defect in BCs To examine whether the abnormal extension and accumulation of polarity and AJ proteins in rab7-/- cells were caused by vesicle transport defect we utilized endocytosis assay to examine the ratio of internalized to membrane-bound E-cadherin In wild type egg chambers the migratory BCs showed 1 6 fold more E-cadherin uptake in comparison with immotile epithelial cells Moreover 2 2 fold of internalized E-cad was observed in rab7-knockdown follicle cells comparing to wild type Taken together we suggest a model that the blockage of endocytosis induced by defective rab7 might contribute to mislocalization of Crumbs and AJ proteins and further impair motility of BCs

Date of Award	2016 Sept 5
Original language	English
Supervisor	Chuen-Chuen Jang (Supervisor)