Abstract
ABSTRACTColour patterns of adult fish are composed of several different types of pigment cells distributing in the skin during juvenile development. The zebrafish, Danio rerio, displays a striking pattern of dark stripes of melanophores interspersed with light stripes of xanthophores. A third cell type, silvery iridophores, contributes to both stripes and plays a crucial role in adult pigment pattern formation. Several mutants deficient in iridophore development display similar adult phenotypes with reduced numbers of melanophores and defects in stripe formation. This indicates a supporting role of iridophores for melanophore development and maintenance. One of these mutants, rose (rse), encodes the Endothelin receptor b1a. Here we describe a new mutant in zebrafish, karneol (kar), which has a phenotype similar to weak alleles of rse with a reduction in iridophore numbers and defects of adult pigment patterning. We show that, unlike rse, kar is not required in iridophores. The gene defective in the kar mutant codes for an endothelin-converting enzyme, Ece2, which activates endothelin ligands by proteolytic cleavage. By morpholino-mediated knockdown, we identify Endothelin 3b (Edn3b) as the ligand for endothelin receptor signalling in larval iridophores. Thus, Endothelin signalling is involved in iridophore development, proliferation and stripe morphogenesis in larvae as well as adult zebrafish. In mammals the pathway is required for melanocyte development; therefore, our results indicate a previously unrecognized close evolutionary relationship between iridophores in zebrafish and melanocytes in mammals.
Highlights
Adult zebrafish display a characteristic body and fin pigmentation pattern of alternating dark stripes and light interstripes
Chimeric animals obtained by blastula transplantations revealed that in the case of shd, rse and tra the genes are autonomously required in iridophores, while mutant melanophores and xanthophores are not affected and can form normal stripes when confronted with wild-type iridophores (Frohnhofer et al, 2013; Krauss et al, 2013)
We identified a mutation in the endothelin-converting enzyme 2 gene resulting in a premature stop and the loss of the C-terminal peptidase domain containing the catalytic centre of the enzyme
Summary
Adult zebrafish display a characteristic body and fin pigmentation pattern of alternating dark stripes and light interstripes. Chimeric animals obtained by blastula transplantations revealed that in the case of shd, rse and tra the genes are autonomously required in iridophores, while mutant melanophores and xanthophores are not affected and can form normal stripes when confronted with wild-type iridophores (Frohnhofer et al, 2013; Krauss et al, 2013). The gene is expressed in pigment cells during early zebrafish development, do not show defects in embryonic iridophores (Parichy et al, 2000), possibly due to redundancy, as zebrafish contain a second paralog, ednrb1b.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
