title: Frazzled/DCC facilitates cardiac cell outgrowth and attachment during Drosophila dorsal vessel formation.
abstract: Drosophila embryonic dorsal vessel (DV) morphogenesis is a highly stereotyped process that involves the migration and morphogenesis of 52 pairs of cardioblasts (CBs) in order to form a linear tube. This process requires spatiotemporally-regulated localization of signaling and adhesive proteins in order to coordinate the formation of a central lumen while maintaining simultaneous adhesion between CBs. Previous studies have shown that the Slit/Roundabout and Netrin/Unc5 repulsive signaling pathways facilitate site-specific loss of adhesion between contralateral CBs in order to form a luminal space. However, the concomitant mechanism by which attraction initiates CB outgrowth and discrete localization of adhesive proteins remains poorly understood. Here we provide genetic evidence that Netrin signals through DCC (Deleted in Colorectal Carcinoma)/UNC-40/Frazzled (Fra) to mediate CB outgrowth and attachment and that this function occurs prior to and independently of Netrin/UNC-5 signaling. fra mRNA is expressed in the CBs prior to and during DV morphogenesis. Loss-of-fra-function results in significant defects in cell shape and alignment between contralateral CB rows. In addition, CB outgrowth and attachment is impaired in both fra loss- and gain-of-function mutants. Deletion of both Netrin genes (NetA and NetB) results in CB attachment phenotypes similar to fra mutants. Similar defects are also seen when both fra and unc5 are deleted. Finally we show that Fra accumulates at dorsal and ventral leading edges of paired CBs, and this localization is dependent upon Netrin. We propose that while repulsive guidance mechanisms contribute to lumen formation by preventing luminal domains from coming together, site-specific Netrin/Frazzled signaling mediates CB attachment.
authors.affiliation: Department of Pathology and Laboratory Medicine Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 675 Hoes Lane, Piscataway, NJ 08854, USA.
authors.forename: Frank D
authors.initials: FD
authors.lastname: Macabenta
authors.forename: Amber G
authors.initials: AG
authors.lastname: Jensen
authors.forename: Yi-Shan
authors.initials: YS
authors.lastname: Cheng
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Kramer
authors.forename: Sunita G
authors.initials: SG
authors.lastname: Kramer
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D049109:Cell Proliferation; D004330:Drosophila / Q000196:embryology*; D029721:Drosophila Proteins / Q000502:physiology; D005260:Female; D006321:Heart / Q000196:embryology*; D008297:Male; D009024:Morphogenesis; D032383:Myocytes, Cardiac / Q000502:physiology*; D009414:Nerve Growth Factors / Q000502:physiology; D000075386:Netrin Receptors; D000075388:Netrin-1; D000075385:Netrins; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000502:physiology
chemical_list: D029721:Drosophila Proteins; D009414:Nerve Growth Factors; C000617352:NetA protein, Drosophila; D000075386:Netrin Receptors; D000075385:Netrins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D025521:Tumor Suppressor Proteins; C000617310:fra protein, Drosophila; C556033:unc-5 protein, Drosophila; D000075388:Netrin-1
keywords: Cardiac; DCC; Dorsal vessel; Drosophila; Frazzled; Netrin