A Chemico-Genetic Analysis of Pigment Pattern Formation in the Zebrafish Mutant Parade

  • Sarah Colanesi

Student thesis: Doctoral ThesisPhD


Pigment patterns of zebrafish are a beautiful example in which to study key processes of vertebrate development such as neural crest cell migration and patterning of neural crest-derived cell types. This can for example be achieved by characterizing mutants like parade in which pigment cell development is abnormal.Here, we present a chemico-genetic study of the pigment pattern mutant parade; uniquely, this mutant displays ectopic pigment cells in the ventral medial pathway of the trunk but the characteristic stripe pattern of zebrafish embryos is unaffected.Using a positional cloning approach, we have identified the parade gene as the cell surface receptor ednra2. This was further confirmed in transient knock-down assays.Combined sequencing data from three different parade alleles strongly indicates that the mutation disrupts ednra2 receptor function by deleting C-terminal regulatory and structural residues.To expand the available molecular tools in pigment cell research, notably to chemically dissect the parade phenotype, we have participated in small molecule screening for inhibitors of pigment cell development. From this, we have isolated 57 compounds which robustly alter the development of melanophores and iridophores in wild-type embryos; 26 of these compounds additionally affect the parade phenotype, primarily by rescuing the ectopic pigment cells. Notably, chemical rescue has shown that the MEK pathway is important for the development of the parade phenotype.Our study therefore adds to our understanding of pigment pattern formation in zebrafish embryos and reveals novel functions for ednra2 in dorso-ventral patterning and cell type specification of neural crest derivatives.
Date of Award18 Sept 2012
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorRobert Kelsh (Supervisor)


  • pigment pattern
  • melanocyte
  • endothelin receptors
  • chemical screening

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