Fate of the mammalian cranial neural crest

The vertebrate neural crest is a pluripotent cell population derived from the lateral ridges of the neural plate during early stages of embryogenesis. Neural crest cells disperse from the dorsal surface of the neural tube and migrate extensively through the embryo, giving rise to a wide variety of differentiated cell types (Romer, 1972; Noden, 1983; Tan and Morriss-Kay, 1986; Bronner-Fraser, 1993). Considerable progress has been made in recent years towards understanding how this important population of pluripotent cells is initially established in the early embryo, and how genetic and epigenetic mechanisms mediate their subsequent lineage segregation, differentiation and final contribution to a particular cell type (see review by LaBonne and BronnerFraser, 1999). During craniofacial development, neural crest cells migrate ventrolaterally as they populate the branchial arches. The proliferative activity of these crest cells produces the discrete swellings that demarcate each branchial arch. As these ectodermally derived cells migrate, they contribute extensively to the formation of mesenchymal structures in the head and neck. Cell labeling studies have demonstrated that neuroectoderm cells of rhombomeres 1-4 (r1-4) in the forming posterior midbrain and anterior hindbrain transform into CNC cells, which migrate into the first branchial arch and thereafter reside within the maxillary and mandibular prominences (Osumi-Yamashita et al., 1990; Serbedzija et al., 1992; 1671 Development 127, 1671-1679 (2000) Printed in Great Britain © The Company of Biologists Limited 2000 DEV4301