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Zebrafish endzone regulates neural crest-derived chromatophore differentiation and morphology.

Arduini BL, Gallagher GR, Henion PD - PLoS ONE (2008)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Center for Molecular Neurobiology, Ohio State University, Columbus, Ohio, United States of America.

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.

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Melanophore cell morphology changes in enz mutant embryos.(A, B) At 27 hpf, wild-type melanophores are large, stellate and well-pigmented (A). enz melanophores are also large and stellate at this stage, but are pale compared to wildtype (B). (C, D) By 31 hpf, enz melanophore begin to transition to a punctate morphology (D), while wild-type melanophores remain large with many processes (C). (E, F) Wild-type (E) and enz mutant (F) embryos at 34.5 hpf. The morphological transition of melanophores in enz homozygotes continues in a rostro-caudal wave and is complete by approximately 48 hpf. (G–J) At 36 hpf, melanosomes are distributed throughout the cytoplasm of wild-type melanophores, reflecting the stellate morphology of these cells (G). (H) dct mRNA (red) is likewise distributed in the extensive processes of wild-type cells (arrowheads). Punctate distribution of melanosomes (I) and dct mRNA (J, red) in enzos18 mutant melanophores is identical at 36 hpf reflecting cell shape change.
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pone-0002845-g005: Melanophore cell morphology changes in enz mutant embryos.(A, B) At 27 hpf, wild-type melanophores are large, stellate and well-pigmented (A). enz melanophores are also large and stellate at this stage, but are pale compared to wildtype (B). (C, D) By 31 hpf, enz melanophore begin to transition to a punctate morphology (D), while wild-type melanophores remain large with many processes (C). (E, F) Wild-type (E) and enz mutant (F) embryos at 34.5 hpf. The morphological transition of melanophores in enz homozygotes continues in a rostro-caudal wave and is complete by approximately 48 hpf. (G–J) At 36 hpf, melanosomes are distributed throughout the cytoplasm of wild-type melanophores, reflecting the stellate morphology of these cells (G). (H) dct mRNA (red) is likewise distributed in the extensive processes of wild-type cells (arrowheads). Punctate distribution of melanosomes (I) and dct mRNA (J, red) in enzos18 mutant melanophores is identical at 36 hpf reflecting cell shape change.

Mentions: To determine whether appropriate numbers of chromatophores are generated in enz mutant embryos, we counted differentiated melanophores and iridiphores in enz homozygotes and wild-type siblings. At 4 dpf, the number of melanophores in enz mutant embryos is significantly reduced compared to wild-type siblings (P<0.0001, Table 1). Likewise, iridiphore numbers are reduced in enz homozygotes compared to wild-type siblings at 6 dpf (P<0.0001, Table 1). In both cases, only about 75% of the wild-type complement of each class of chromatophores is present in enz mutants at the stages examined. Quantification of xanthophore numbers was precluded by indistinct boundaries and overlap between these cells. However, methylene blue staining (see below) at 3 dpf, as well as fms expression between 48 and 53 hpf, revealed that while many xanthophores are present in enz homozygotes, their numbers are reduced in a manner qualitatively similar to that of melanophores and iridiphores (Figure 5 and data not shown). Thus, enz mutations appear to result in similar reductions in the numbers of differentiated chromatophores, while other neural crest-derived cell types are unaffected.


Zebrafish endzone regulates neural crest-derived chromatophore differentiation and morphology.

Arduini BL, Gallagher GR, Henion PD - PLoS ONE (2008)

Melanophore cell morphology changes in enz mutant embryos.(A, B) At 27 hpf, wild-type melanophores are large, stellate and well-pigmented (A). enz melanophores are also large and stellate at this stage, but are pale compared to wildtype (B). (C, D) By 31 hpf, enz melanophore begin to transition to a punctate morphology (D), while wild-type melanophores remain large with many processes (C). (E, F) Wild-type (E) and enz mutant (F) embryos at 34.5 hpf. The morphological transition of melanophores in enz homozygotes continues in a rostro-caudal wave and is complete by approximately 48 hpf. (G–J) At 36 hpf, melanosomes are distributed throughout the cytoplasm of wild-type melanophores, reflecting the stellate morphology of these cells (G). (H) dct mRNA (red) is likewise distributed in the extensive processes of wild-type cells (arrowheads). Punctate distribution of melanosomes (I) and dct mRNA (J, red) in enzos18 mutant melanophores is identical at 36 hpf reflecting cell shape change.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2483736&req=5

pone-0002845-g005: Melanophore cell morphology changes in enz mutant embryos.(A, B) At 27 hpf, wild-type melanophores are large, stellate and well-pigmented (A). enz melanophores are also large and stellate at this stage, but are pale compared to wildtype (B). (C, D) By 31 hpf, enz melanophore begin to transition to a punctate morphology (D), while wild-type melanophores remain large with many processes (C). (E, F) Wild-type (E) and enz mutant (F) embryos at 34.5 hpf. The morphological transition of melanophores in enz homozygotes continues in a rostro-caudal wave and is complete by approximately 48 hpf. (G–J) At 36 hpf, melanosomes are distributed throughout the cytoplasm of wild-type melanophores, reflecting the stellate morphology of these cells (G). (H) dct mRNA (red) is likewise distributed in the extensive processes of wild-type cells (arrowheads). Punctate distribution of melanosomes (I) and dct mRNA (J, red) in enzos18 mutant melanophores is identical at 36 hpf reflecting cell shape change.
Mentions: To determine whether appropriate numbers of chromatophores are generated in enz mutant embryos, we counted differentiated melanophores and iridiphores in enz homozygotes and wild-type siblings. At 4 dpf, the number of melanophores in enz mutant embryos is significantly reduced compared to wild-type siblings (P<0.0001, Table 1). Likewise, iridiphore numbers are reduced in enz homozygotes compared to wild-type siblings at 6 dpf (P<0.0001, Table 1). In both cases, only about 75% of the wild-type complement of each class of chromatophores is present in enz mutants at the stages examined. Quantification of xanthophore numbers was precluded by indistinct boundaries and overlap between these cells. However, methylene blue staining (see below) at 3 dpf, as well as fms expression between 48 and 53 hpf, revealed that while many xanthophores are present in enz homozygotes, their numbers are reduced in a manner qualitatively similar to that of melanophores and iridiphores (Figure 5 and data not shown). Thus, enz mutations appear to result in similar reductions in the numbers of differentiated chromatophores, while other neural crest-derived cell types are unaffected.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Center for Molecular Neurobiology, Ohio State University, Columbus, Ohio, United States of America.

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.

Show MeSH
Related in: MedlinePlus