title: Eph and Ephrin function in dispersal and epithelial insertion of pigmented immunocytes in sea urchin embryos.
abstract: The mechanisms that underlie directional cell migration are incompletely understood. Eph receptors usually guide migrations of cells by exclusion from regions expressing Ephrin. In sea urchin embryos, pigmented immunocytes are specified in vegetal epithelium, transition to mesenchyme, migrate, and re-enter ectoderm, distributing in dorsal ectoderm and ciliary band, but not ventral ectoderm. Immunocytes express Sp-Eph and Sp-Efn is expressed throughout dorsal and ciliary band ectoderm. Interfering with expression or function of Sp-Eph results in rounded immunocytes entering ectoderm but not adopting a dendritic form. Expressing Sp-Efn throughout embryos permits immunocyte insertion in ventral ectoderm. In mosaic embryos, immunocytes insert preferentially in ectoderm expressing Sp-Efn. We conclude that Sp-Eph signaling is necessary and sufficient for epithelial insertion. As well, we propose that immunocytes disperse when Sp-Eph enhances adhesion, causing haptotactic movement to regions of higher ligand abundance. This is a distinctive example of Eph/Ephrin signaling acting positively to pattern migrating cells.
authors.affiliation: Department of Biology, University of Victoria, Victoria, Canada.
authors.forename: Oliver A
authors.initials: OA
authors.lastname: Krupke
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada.
authors.forename: Ivona
authors.initials: I
authors.lastname: Zysk
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada.
authors.forename: Dan O
authors.initials: DO
authors.lastname: Mellott
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada.
authors.forename: Robert D
authors.identifier: 0000-0001-5527-4410
authors.initials: RD
authors.lastname: Burke
mesh_terms: D000818:Animals; D002465:Cell Movement; D036342:Ephrins / Q000378:metabolism*; D004848:Epithelium / Q000196:embryology*; D036082:Receptor, EphA1 / Q000378:metabolism*; D012617:Sea Urchins / Q000196:embryology*
chemical_list: D036342:Ephrins; D036082:Receptor, EphA1
keywords: Strongylocentrouts; deuterostome; purple sea urchin; purpuratus