Mechanisms of lineage segregation in the avian dermomyotome.

The somite and its intermediate derivatives, sclerotome and dermomyotome (DM), are composed of distinct subdomains based on lineage analysis and gene expression patterns. This sets the grounds for elucidating the mechanisms underlying differential cell specification and morphogenesis. By examining the in vivo roles of N-cadherin on discrete domains of the somitic epithelium at various times, our recent studies highlight the existence of a regional and temporal heterogeneity in cellular responsiveness. As examples of this assortment, we document a coupling between asymmetric cell division and fate segregation in the DM sheet, sequential effects of N-cadherin-mediated adhesion on early myogenic specification compared to later myofiber patterning, and a differential behavior of pioneer myoblasts compared to later myogenic waves.