Neural crest and the origin of species‐specific pattern

Abstract

SummaryFor well over half of the 150 years since the discovery of the neural crest, the special ability of these cells to function as a source of species‐specific pattern has been clearly recognized. Initially, this observation arose in association with chimeric transplant experiments among differentially pigmented amphibians, where the neural crest origin for melanocytes had been duly noted. Shortly thereafter, the role of cranial neural crest cells in transmitting species‐specific information on size and shape to the pharyngeal arch skeleton as well as in regulating the timing of its differentiation became readily apparent. Since then, what has emerged is a deeper understanding of how the neural crest accomplishes such a presumably difficult mission, and this includes a more complete picture of the molecular and cellular programs whereby neural crest shapes the face of each species. This review covers studies on a broad range of vertebrates and describes neural‐crest‐mediated mechanisms that endow the craniofacial complex with species‐specific pattern. A major focus is on experiments in quail and duck embryos that reveal a hierarchy of cell‐autonomous and non‐autonomous signaling interactions through which neural crest generates species‐specific pattern in the craniofacial integument, skeleton, and musculature. By controlling size and shape throughout the development of these systems, the neural crest underlies the structural and functional integration of the craniofacial complex during evolution.

Migratory patterns and evolutionary plasticity of cranial neural crest cells in ray-finned fishes

“…In the final phase of migration, the endoderm influences CNC differentiation into cartilage precursors (Piotrowski and Nüsslein-Volhard, 2000;David et al, 2002;Crump et al, 2004). Thus, modulations of the head endoderm, and heterochronic and heterotopic alterations of CNC migratory patterns might represent a key source of craniofacial diversity in vertebrates (Schneider, 2018).…”

Morphological diversity of integumentary traits in fowl domestication: Insights from disparity analysis and embryonic development

“…Much of that information derives from experimental embryology, which has demonstrated that epithelial-mesenchymal signaling interactions are the essential basic mechanisms required for the formation and patterning of the vertebrate integument. 66,67 Particularly, the tissue layer that induces many of the integumental structures in vertebrates, and consequently in chickens, is the dermis. 68 For example, the seminal work of Saunders, 69,70 which involved grafting and assessing the interactions between different body regions of chickens throughout development, provided a foundation for further developmental studies on this matter.…”

“…35 In quail-duck chimeras, which are generated by transplanting cranial neural crest cells that give rise to the dermis, the egg tooth takes on the morphological identity of the donor species despite arising entirely from nontransplanted host epidermis. 59,66,67,81 In chickens, as in other vertebrates, colors mostly come either from the accumulation of carotenoids or from the activity of melanocytes (eumelanin [black] and pheomelanin [red]), the latter being neural crest derivatives. 42 Additionally, some contributions to pigmentation come from structural color and the so-called "uncommon colors"; as pterins, porphyns, psittacofulvins.…”

“…Table summarizes the interactions and roles of neural crest during development of the integumentary traits studied in the present work. Much of that information derives from experimental embryology, which has demonstrated that epithelial‐mesenchymal signaling interactions are the essential basic mechanisms required for the formation and patterning of the vertebrate integument . Particularly, the tissue layer that induces many of the integumental structures in vertebrates, and consequently in chickens, is the dermis .…”

“…Quail have an egg tooth at the tip of their beak that is a conical protrusion of hard keratin whereas duck have a leathery and flat epidermal nail . In quail‐duck chimeras, which are generated by transplanting cranial neural crest cells that give rise to the dermis, the egg tooth takes on the morphological identity of the donor species despite arising entirely from non‐transplanted host epidermis …”