Reduced epidermal expression of a PG-M/versican-like proteoglycan in embryos of the white mutant axolotl.

Axolotl embryos have previously been used to study neural crest cell migration. In embryos of the normal wild type, neural crest cells migrate subepidermally to form pigment cells. In the trunk of the white mutant embryo, these cells are unable to migrate, possibly due to an inherited delay in the maturation of the local extracellular matrix. The present investigation reveals a reduced incorporation of [35S]sulfate into PG-M/versican-like proteoglycans synthesized in epidermal explants from the dorsal trunk of white mutant embryos during stages pertinent to migration. This is the major form of proteoglycans in the subepidermal matrix, where they are assembled in large disulfide-stabilized supramolecular complexes. The reduction in [35S]sulfate incorporation is not due to qualitative differences between wild-type and white mutant proteoglycans but is paralleled by a reduced expression of mRNA for the core protein of the PG-M/versican-like proteoglycan. We conclude that a reduced amount of these proteoglycans is produced by the white mutant embryo during the period critical for migration.