Filopodial Activity of the Cardioblast Leading Edge in Drosophila

Abstract

<p>The Drosophila heart arises from two bilateral rows of cardioblasts (CB) that migratedorsally towards the midline and contact their contralateral partners to form the dorsal vessel.Generally, migrating cells rely on the extensions at the leading edge domain. Like other migratingcells, we show that the leading edge of the CBs extends finger-like processes which might play arole in sensing guidance cues during guided migration. Expressing an mCherry-Moesin transgenein the CBs enabled us to characterise the dynamic nature and genetic requirements of thesefilopodial processes. While studying the role of filopodial activity during heart assembly weobserved that CBs extended cellular protrusions towards the internalizing amnioserosa cells.Filopodial activity is low during migration, and rises when the CBs are near the amnioserosacells. However, filopodial contacts are stabilized by interaction with contralateral CBs, not theamnioserosa cells. CB cell bodies can contact their contra lateral partners only after theamnioserosa is fully internalized. We propose that filopodia are generated in response to thepresence of sensory guidance molecules excreted by the amnioserosa cells.Robo/Slit signalling has been previously shown to play a role in CB migration, adhesionand lumen formation. Additionally, studies have shown that Robo/Slit signalling plays a role infilopodial extension in the Drosophila nervous system development. We observed that in embryosin which Robo signaling in the CBs was reduced or absent, the CBs were less active at the LE. Inaddition, the migration speed of CBs in mutant embryos was notably decreased. Based on theseresults, we hypothesize that Robo/Slit signaling plays a role in filopodial extensions.</p>