title: Genetic analysis of steel and the PG-M/versican-encoding gene AxPG as candidates for the white (d) pigmentation mutant in the salamander Ambystoma mexicanum.
abstract: Vertebrate non-retinal pigment cells are derived from neural crest (NC) cells, and several mutations have been identified in the Mexican axolotl Ambystoma mexicanum (Ambystomatidae) that affect the development of these cell lineages. In "white" (d) mutant axolotls, premigratory NC cells differentiate as pigment cells, yet fail to disperse, survive, or both, and this leads to a nearly complete absence of pigment cells in the skin. Previous studies revealed that d affects pigment cell development non-autonomously, and have reported differences between white and wild-type axolotls in the structure and composition of the extracellular matrix through which NC and pigment cells migrate. Here we test the correspondence of d and two candidate genes: steel and AxPG. In amniotes, Steel encodes the cytokine Steel factor (mast cell growth factor; stem cell factor; kit ligand), which is expressed along the migratory pathways of melanocyte precursors and is required by these cells for their migration and survival; mammalian Steel mutants resemble white mutant axolotls in having a deficit or complete absence of pigment cells. In contrast, AxPG encodes a PG-M/versican-like proteoglycan that may promote the migration of A. mexicanum pigment cells, and AxPG expression is reduced in white mutant axolotls. We cloned a salamander orthologue of steel and used a partial genetic linkage map of Ambystoma to determine the genomic locations of steel, AxPG, and d. We show that the three genes map to different linkage groups, excluding steel and AxPG as candidates for d.
authors.affiliation: Section of Integrative Biology, University of Texas at Austin, Austin TX 78712-1064, USA. dparichy@genetics.wustl.edu
authors.forename: D M
authors.initials: DM
authors.lastname: Parichy
authors.forename: M
authors.initials: M
authors.lastname: Stigson
authors.forename: S R
authors.initials: SR
authors.lastname: Voss
mesh_terms: D000558:Ambystoma mexicanum / Q000196:embryology / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D011508:Chondroitin Sulfate Proteoglycans / Q000235:genetics*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D037181:Lectins, C-Type; D008969:Molecular Sequence Data; D009154:Mutation; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012880:Skin Pigmentation / Q000235:genetics*; D019089:Stem Cell Factor / Q000235:genetics*; D053675:Versicans
chemical_list: D011508:Chondroitin Sulfate Proteoglycans; D018076:DNA, Complementary; D037181:Lectins, C-Type; D019089:Stem Cell Factor; D053675:Versicans