Multiple requirements for Rab GTPases in the development ofDrosophilatracheal dorsal branches and terminal cells

Abstract

14Biosciences 15 Correspondence to M.L., Abstract 18The tracheal epithelium in fruit fly larvae is a popular model for multi-and unicellular 19 migration and morphogenesis. Like all epithelial cells, tracheal cells use Rab 20GTPases to organise their internal membrane transport, resulting in the specific 21 localisation or secretion of proteins on the apical or basal membrane compartments. 22Some contributions of Rabs to junctional remodelling and governance of tracheal 23 lumen contents are known, but it is reasonable to assume that they play important 24 further roles in morphogenesis. This pertains in particular to terminal tracheal cells, 25 specialised branch-forming cells that drastically reshape both their apical and basal 26 membrane during the larval stages. We performed a loss-of-function screen in the 27 tracheal system, knocking down endogenously tagged alleles of 26 Rabs by 28 targeting the tag via RNAi. This revealed that at least 14 Rabs are required to 29 ensure proper cell fate specification and migration of the dorsal branches, as well as 30 their epithelial fusion with the contralateral dorsal branch. The screen implicated four 31 Rabs in the subcellular morphogenesis of terminal cells themselves. Further tests 32suggested residual gene function after knockdown, leading us to discuss the 33 limitations of this approach. We conclude that more Rabs than identified here may 34 be important for tracheal morphogenesis, and that the tracheal system offers great 35 opportunities for studying several Rabs that have barely been characterised so far. 36

Systematic functional analysis of Rab GTPases reveals limits of neuronal robustness inDrosophila

“…Rab GTPases have been analyzed in several comparative studies in order to gain a systematic view of membrane trafficking in cells (Best and Leptin, 2020; Chan et al, 2011; Dunst et al, 2015; Gillingham et al, 2014; Gurkan et al, 2005; Jin et al, 2012; Pfeffer, 1994; Stenmark, 2009; Zerial and McBride, 2001). All comparative studies to date have been based on expression profiling, the expression of GDP and GTP-locked Rabs or RNAi.…”