Collagen type VI in neural crest development: distribution in situ and interaction with cells in vitro.

We have examined the spatio-temporal distribution of collagen type VI (Col VI) during neural crest development in vivo and its ability to promote neural crest cell attachment and migration in vitro. An affinity purified antiserum and chain-specific monoclonal antibodies against chicken Col VI were employed to immunolocalize the collagen in tissue sections and by immunoblotting. At stages of initial neural crest cell migration, the alpha 1(VI) and alpha 2(VI) chains were immunolocalized in apposition with basement membranes of the neural tube, somites, notochord and ectoderm, whereas no immunoreactivity was seen for the alpha 3(VI) chain. Immunoblotting analysis confirmed the expression of alpha 1(VI) and alpha 2(VI) chains and the lack of detectable immunoreactivity for the alpha 3(VI) chain at these early phases of neural crest development. Conversely, at advanced phases of migration and following gangliogenesis, expression of alpha 3(VI) chain coincided with that of alpha 1(VI) and alpha 2(VI) chains in apposition with basement membranes, around the dorsal root ganglia, and in fibrillar arrangements within the developing dermis and ventral sclerotome. The ability of Col VI to promote neural crest cell attachment and migration was tested in vitro using quantitative assays for these processes. Both native microfilaments and isolated tetramers of Col VI strongly promoted neural crest cell attachment and migration. Optimal stimulation of neural crest cell adhesion and migration was dependent upon structural integrity of Col VI since unfolded and disassembled alpha chains only weakly promoted cell attachment and were virtually inactive in supporting cell movement. The importance of a native macromolecular organization of Col VI further was analyzed in experiments in which dissociated tetramers were reassociated by Ca(2+)- and temperature-dependent self-aggregation. In contrast to native microfilaments, these oligomeric complexes were less effective in promoting neural crest cell movement, but still retained the ability to stimulate maximal cell attachment. The results indicate that Col VI is a primary component of the extracellular matrix deposited along neural crest migratory pathways, where it may participate in the regulation of cell movement by functioning as a migratory substrate. The ability of Col VI to promote neural crest cell adhesion and motility is highly dependent upon maintainance of a native macromolecular arrangement.