Fate and Roles of the Neural Crest, Mesoderm, and Epithelium

Abstract

The derivatives of the neural crest in avians, amphibians, and mammals has been determined by a combination of in vivo studies including radioactive thymidine tracing, labelling with the lipophilic dye, DiI, retroviral labelling, chimaeric grafting studies, and more recently transgenic approaches where the progeny of the cranial neural crest cells has been followed by marking the neural crest cells with Lac-Z (Noden 1978a,b, 1983a,b, 1986,1988; Serbedzija et al. 1992; Poelmann and Gittenberger-de-Groot 1999; Yamauchi et al. 1999; Chai et al. 2000; Jiang et al. 2000). These studies have revealed that the cranial neural crest (CNC), as is the trunk neural crest, is pluripotent, contributing to the central and peripheral nervous system, pigment cells, and connective tissue components. However, in contrast to trunk neural crest, CNC also gives rise to smooth muscle cells and hard tissues such as the facial skeleton and components of the teeth (Fig. 4; Table 2; Le Lièvre and Le Douarin 1975; Noden 1978a,b, 1983a,b, 1988, 1991a,b; Beall and Rosenquist 1990; Couly et al. 1992, 1993, 1995; Le Douarin et al. 1993; Imai et al. 1996; Köntges and Lumsden 1996; Chai et al. 2000). Until recently in higher vertebrates, this skeletogenic ability appears to be unique to the CNC, and hence trunk neural crest cells when grafted into the cranial environment cannot contribute to hard tissue structures, although they are capable of forming other mesectodermal derivatives (Nakamura and Ayer-le Lievre 1982). However, a recent report has shown that chick trunk neural crest cells can give rise to skeletal tissue under the appropriate conditions (McGonnell and Graham, 2002, Curr. Biol. 12: 767–771). In contrast, cranial neural crest cells retain their ability to form cartilage when transplanted into the trunk, yielding small cartilage nodules in the kidney (Le Douarin and Teillet 1974). Likewise, trunk neural crest cells cannot contribute to the smooth muscle walls of blood vessels or the meninges when grafted into the developing head (Le Douarin et al. 1977; Etchevers et al. 1999).