Glycoconjugates mark a transient barrier to neural crest migration in the chicken embryo.

We report that two molecular markers correlate with a transient inhibition of neural crest cell entry into the dorsolateral path between the ectoderm and the somite in the avian embryo. During the period when neural crest cells are excluded from the dorsolateral path, both peanut agglutinin lectin (PNA)-binding activity and chondroitin-6-sulfate (C6S) immunoreactivity are expressed within this path. Both markers decline as neural crest cells enter. Moreover, both markers are absent after an experimental manipulation that accelerates neural crest entry into this path. Specifically, dermamyotome deletions abolish expression of both markers and allow neural crest cells to enter the dorsolateral path precociously. After partial deletions, dermatome remnants remain. These remnants retain PNA and C6S labeling and impede migration locally. Local glycoconjugate expression thus correlates directly with avoidance responses. Since both PNA-binding activity and C6S expression also typify inhibitory somitic tissues, molecules indicated by these markers (or co-regulated molecules) are likely to inhibit both neural crest and axon advance.