ZFIN ID: ZDB-PUB-190308-8
Countershading in zebrafish results from an Asip1 controlled dorsoventral gradient of pigment cell differentiation
Cal, L., Suarez-Bregua, P., Comesaña, P., Owen, J., Braasch, I., Kelsh, R., Cerdá-Reverter, J.M., Rotllant, J.
Date: 2019
Source: Scientific Reports   9: 3449 (Journal)
Registered Authors: Braasch, Ingo, Cerdá-Reverter, José Miguel, Kelsh, Robert, Rotllant, Josep
Keywords: none
MeSH Terms:
  • Agouti Signaling Protein/genetics*
  • Amino Acid Sequence
  • Animals
  • Body Patterning/genetics*
  • CRISPR-Cas Systems
  • Cell Differentiation
  • Gene Targeting
  • Genetic Loci
  • Loss of Function Mutation
  • Phenotype
  • Pigmentation/genetics*
  • Zebrafish/genetics*
PubMed: 30837630 Full text @ Sci. Rep.
Dorso-ventral (DV) countershading is a highly-conserved pigmentary adaptation in vertebrates. In mammals, spatially regulated expression of agouti-signaling protein (ASIP) generates the difference in shading by driving a switch between the production of chemically-distinct melanins in melanocytes in dorsal and ventral regions. In contrast, fish countershading seemed to result from a patterned DV distribution of differently-coloured cell-types (chromatophores). Despite the cellular differences in the basis for counter-shading, previous observations suggested that Agouti signaling likely played a role in this patterning process in fish. To test the hypotheses that Agouti regulated counter-shading in fish, and that this depended upon spatial regulation of the numbers of each chromatophore type, we engineered asip1 homozygous knockout mutant zebrafish. We show that loss-of-function asip1 mutants lose DV countershading, and that this results from changed numbers of multiple pigment cell-types in the skin and on scales. Our findings identify asip1 as key in the establishment of DV countershading in fish, but show that the cellular mechanism for translating a conserved signaling gradient into a conserved pigmentary phenotype has been radically altered in the course of evolution.