Early specification and development of rabbit neural crest cells

Abstract

The phenomenal migratory and differentiation capacity of neural crest cells has been well established across model organisms. While the earliest stages of neural crest development have been investigated in non-mammalian model systems such as Xenopus and Aves, the early specification of this cell population has not been evaluated in mammalian embryos, of which the murine model is the most prevalent. Towards a more comprehensive understanding of mammalian neural crest formation and human comparative studies, we have used the rabbit as a mammalian system for the study of early neural crest specification and development. We examine the expression profile of well-characterized neural crest markers in rabbit embryos across developmental time from early gastrula to later neurula stages, and provide a comparison to markers of migratory neural crest in the chick. Importantly, we apply explant specification assays to address the pivotal question of mammalian neural crest ontogeny, and provide the first evidence that a specified population of neural crest cells exists in the rabbit gastrula prior to the overt expression of neural crest markers. Finally, we demonstrate that FGF signaling is necessary for early rabbit neural crest formation, as SU5402 treatment strongly represses neural crest marker expression in explant assays. This study pioneers the rabbit as a model for neural crest development, and provides the first demonstration of mammalian neural crest specification and the requirement of FGF signaling in this process.

Specification and formation of the neural crest: Perspectives on lineage segregation

“…A step toward explaining this multipotential came from Basch et al (2006), which described a model of early neural crest specification during gastrulation and prior to the formation of definitive germ layers. Further support for this study has come from additional studies in chick, and in rabbit embryos describing the gastrula stage specification of neural crest (Betters et al, 2018;Patthey et al, 2008). Recent studies using human neural crest derived from human embryonic stem cells also support an early neural crest specification, independent of definitive neural and mesodermal tissue (Leung et al, 2016).…”

“…Expression analysis also suggested a mesoderm independent role of FGF signaling, as FGFR1/4 are expressed in perspective neural crest epiblast during these stages, but not in the mesoderm (Lunn et al, 2007;Stuhlmiller & García-Castro, 2012b). Supporting these findings, recent work in rabbit supports a mesoderm-independent specification of neural crest, which is dependent upon FGF signaling (Betters et al, 2018). In this report, explants from the prospective neural crest territory in the gastrula rabbit embryo were unable to express the neural crest markers Pax7 and Sox10 in the presence of an FGF inhibitor.…”

“…The neural plate border is characterized by the expression of transcription factors including Zic1, Pax3/7, and Gbx2, among others, which are involved in activating a cascade of factors that lead to the maintenance of the neural crest state and later migratory and differentiation networks. Integrative efforts from numerous models including Xenopus , chick, zebrafish, and mouse, and more recently in basal vertebrates such as lamprey and hagfish (Nikitina, Sauka‐Spengler, & Bronner‐Fraser, ; Ota, Kuraku, & Kuratani, ; Sauka‐Spengler, Meulemans, Jones, & Bronner‐Fraser, ), and other mammalian models such as rabbit (Betters et al, ), and human embryonic stem cell‐based systems (Leung et al, ), have informed a neural crest GRN representing the hierarchical and combinatorial interactions between signaling molecules and transcription factors governing neural crest formation (Prasad et al, ; Rogers & Nie, ; Sauka‐Spengler & Bronner‐Fraser, ; Simoes‐Costa & Bronner, ).…”

Blastula stage specification of avian neural crest

“…In Xenopus, a specified region of 65 NC was shown to exist coincident with the completion of gastrulation (Mancilla and Mayor, 66 1996). Furthermore, mammalian work using rabbit embryos and a human model of NC 67 formation based on embryonic stem cells (Betters et al, 2018;Leung et al, 2016), also 68 suggest that early anterior NC is specified prior to gastrulation and independent from 69 definitive neural and mesodermal tissues. In Xenopus, a specified region of NC was 70 shown to exist coincident with the completion of gastrulation (Mancilla and Mayor, 1996); 71 however, recent work suggests a pre-gastrula origin of NC, and proposed that prospective 72 NC retain stemness markers and pluripotency from epiblast cells (Buitrago-Delgado et 73 al., 2015).…”

The RNA helicase DDX3 induces neural crest by promoting AKT activity

“…Nearly all of our knowledge on the induction of NC was obtained from studies using Xenopus and other non-mammalian vertebrates such as chicks, due to technical difficulties that have been encountered in mice (Barriga et al, 2015;Betters et al, 2018).…”