Abstract
The development of neural crest-derived pigment cells has been studied extensively as a model for cellular differentiation, disease and environmental adaptation. Neural crest-derived chromatophores in the zebrafish (Danio rerio) consist of three types: melanophores, xanthophores and iridiphores. We have identified the zebrafish mutant endzone (enz), that was isolated in a screen for mutants with neural crest development phenotypes, based on an abnormal melanophore pattern. We have found that although wild-type numbers of chromatophore precursors are generated in the first day of development and migrate normally in enz mutants, the numbers of all three chromatophore cell types that ultimately develop are reduced. Further, differentiated melanophores and xanthophores subsequently lose dendricity, and iridiphores are reduced in size. We demonstrate that enz function is required cell autonomously by melanophores and that the enz locus is located on chromosome 7. In addition, zebrafish enz appears to selectively regulate chromatophore development within the neural crest lineage since all other major derivatives develop normally. Our results suggest that enz is required relatively late in the development of all three embryonic chromatophore types and is normally necessary for terminal differentiation and the maintenance of cell size and morphology. Thus, although developmental regulation of different chromatophore sublineages in zebrafish is in part genetically distinct, enz provides an example of a common regulator of neural crest-derived chromatophore differentiation and morphology.
Highlights
The neural crest is a transient vertebrate embryonic cell population that gives rise to a wide variety of cell types, including chromatophores, craniofacial cartilage, and neurons and glia of the peripheral nervous system [1]
All four enz alleles are recessive. These alleles vary in the severity of the developmental defects in all three chromatophore phenotypes. enzos15 is less severe than enzb431, enzos7, and enzos18, which are similar in expressivity
Zebrafish enz is selectively required during neural crest development for the terminal differentiation and maintenance of cell morpholgy in late embryonic and larval chromatophores
Summary
The neural crest is a transient vertebrate embryonic cell population that gives rise to a wide variety of cell types, including chromatophores, craniofacial cartilage, and neurons and glia of the peripheral nervous system [1]. This array of neural crestderived cell types has long been of interest in studying the mechanisms of cell diversification among embryonic cell populations. Hundreds of mouse coat color mutants have been identified, covering over 100 loci, which affect multiple cellular processes [4,5] Many of these mutations in mice have proved to be medically relevant as models for human diseases involving the same genes [9]. In addition to the isolation of several zebrafish chromatophore mutants that arose spontaneously [12,13], numerous mutagenesis screens have yielded over 100 mutations affecting various processes in the development of different combinations of the chromatophore types [6,14,15,16,17]
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