Effects of extracellular matrix molecules on subepidermal neural crest cell migration in wild type and white mutant (dd) axolotl embryos

Migration of neural crest (NC) derived pigment cells is restricted in the white mutant (dd) axolotl embryo (Ambystoma mexicanum). Transplantations between mutant and wild type embryos show that the extracellular matrix (ECM) of the white mutant is unable to support the migration of prospective pigment cells in wild type embryos (Löfberg et al., 1989, Dev. Biol. 131:168-181). In the present study, we test the effects of various purified ECM molecules on NC cell migration in the subepidermal migratory pathway of wild type (D/-) and white mutant (dd) axolotl embryos. We adsorbed the ECM molecules onto membrane microcarriers, which were then implanted under the epidermis. Fibronectin (FN), tenascin (TN), collagens I and VI, and a chick aggrecan stimulated migration in both types of embryos. Laminin-nidogen, rat chondrosarcoma aggrecan, and shark aggrecan stimulated migration in dd embryos but did not affect migration in D/- embryos. Collagen III, fibromodulin and bovine aggrecan had no effect on migration in either type of embryo. NC cells did not migrate on control microcarriers, which lacked ECM molecules. Some cells observed contacting, and presumably migrating on, coated microcarriers could be identified as pigment cells by their ultrastructure. Enzymatic digestion in vivo with chondroitinase ABC had no effect on NC cell migration. The neutral or stimulatory effect of the aggrecans is surprising; when tested in vitro they inhibited NC cell migration. The effect of three-dimensionality and other molecules present either in the embryonic ECM or in solution may overcome the inhibitory effect of aggrecans.