ABSTRACT
Odontodes are exoskeletal structures formed by reciprocal interactions between epithelial cells and the underlying neural crest (NC), a multipotent embryonic stem cell population. The NC originates within the forming central nervous system (CNS), but then undergoes an epithelial-to-mesenchymal transition to migrate throughout the periphery and give rise to many cell types. Sometimes referred to as the fourth germ layer, the NC has a broad developmental potential that has significantly expanded the vertebrate body plan by providing an enormous variety of derivatives. The most striking innovations of NC include odontoblasts that deposit the dentin of odontodes and structures comprising these tissues, such as jaws, visceral arches, teeth, or protective dermal exoskeleton. Here, we review how the NC arises in early vertebrate embryos and contributes to diverse cell types and tissues, with a focus on the teeth and protective dermal exoskeleton of ancient and some extant vertebrates.
