title: Heterotypic interactions regulate cell shape and density during color pattern formation in zebrafish.
abstract: The conspicuous striped coloration of zebrafish is produced by cell-cell interactions among three different types of chromatophores: black melanophores, orange/yellow xanthophores and silvery/blue iridophores. During color pattern formation xanthophores undergo dramatic cell shape transitions and acquire different densities, leading to compact and orange xanthophores at high density in the light stripes, and stellate, faintly pigmented xanthophores at low density in the dark stripes. Here, we investigate the mechanistic basis of these cell behaviors in vivo, and show that local, heterotypic interactions with dense iridophores regulate xanthophore cell shape transition and density. Genetic analysis reveals a cell-autonomous requirement of gap junctions composed of Cx41.8 and Cx39.4 in xanthophores for their iridophore-dependent cell shape transition and increase in density in light-stripe regions. Initial melanophore-xanthophore interactions are independent of these gap junctions; however, subsequently they are also required to induce the acquisition of stellate shapes in xanthophores of the dark stripes. In summary, we conclude that, whereas homotypic interactions regulate xanthophore coverage in the skin, their cell shape transitions and density is regulated by gap junction-mediated, heterotypic interactions with iridophores and melanophores.
authors.affiliation: Max Planck Institute for Developmental Biology, Spemannstrasse 35, Tübingen 72076, Germany Prateek.mahalwar@tuebingen.mpg.de uwe.irion@tuebingen.mpg.de.
authors.forename: Prateek
authors.initials: P
authors.lastname: Mahalwar
authors.affiliation: Max Planck Institute for Developmental Biology, Spemannstrasse 35, Tübingen 72076, Germany.
authors.forename: Ajeet Pratap
authors.initials: AP
authors.lastname: Singh
authors.affiliation: Max Planck Institute for Developmental Biology, Spemannstrasse 35, Tübingen 72076, Germany.
authors.forename: Andrey
authors.initials: A
authors.lastname: Fadeev
authors.affiliation: Max Planck Institute for Developmental Biology, Spemannstrasse 35, Tübingen 72076, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Nüsslein-Volhard
authors.affiliation: Max Planck Institute for Developmental Biology, Spemannstrasse 35, Tübingen 72076, Germany Prateek.mahalwar@tuebingen.mpg.de uwe.irion@tuebingen.mpg.de.
authors.forename: Uwe
authors.identifier: http://orcid.org/0000-0003-2823-5840
authors.initials: U
authors.lastname: Irion
keywords: Cell-cell interactions; Gap junctions; Iridophores; Melanophores; Pigment pattern formation; Xanthophores; Zebrafish