Rac1 controls epithelial tube length through the apical secretion and polarity pathways.

Kévin Sollier,François J.-M Chartier,Helori-Mael Gaudé,Patrick Laprise

doi:10.1242/bio.015727

Abstract

ABSTRACTThe morphometric parameters of epithelial tubes are critical to the physiology and homeostasis of most organs. In addition, many human diseases are associated with tube-size defects. Here, we show that Rac1 limits epithelial tube elongation in the developing fly trachea by promoting Rab5-dependent endocytosis of the apical determinant Crumbs. Rac1 is also involved in a positive feedback loop with the septate junction protein Coracle. Thereby, Rac1 precludes paracellular diffusion and contributes to the septate junction-dependent secretion of the chitin-modifying enzymes Vermiform and Serpentine, which restrict epithelial tube length independently of Crumbs. Thus, Rac1 is a critical component of two important pathways controlling epithelial tube morphogenesis.

Highlights

Epithelial tubes sustain gas, nutrient and waste exchange to maintain the homeostasis of metazoan tissues
Rac1 limits Crb activity to define dorsal trunk length To explore the role of Rac1 in tubulogenesis, we expressed a dominant negative form of Rac1 (Rac1N17) using the trachealspecific btl-GAL4 driver
Dorsal trunks were over-elongated and convoluted in Rac1N17-expressing embryos compared to dorsal trunks seen in control specimens (Fig. 1A,B,E)

Summary

Introduction

Epithelial tubes sustain gas, nutrient and waste exchange to maintain the homeostasis of metazoan tissues. Crb promotes apical membrane growth and elongation of dorsal trunks independently of, and in parallel to, the luminal extracellular matrix pathway (Laprise et al, 2010). We show that Rac1 defines the length of multicellular epithelial tubes by supporting Verm and Serp secretion, and by promoting Crb endocytosis.

Results

Conclusion