NR6A1 is essential for neural crest cell specification, formation and survival

Neural crest cells (NCC) are a migratory progenitor cell population unique to vertebrates that contribute to nearly every organ system throughout the body. Disruptions in NCC development can result in congenital disorders (neurocristopathies). Yet, our understanding of the cellular mechanisms and signals that govern mammalian NCC formation remains poor. Here, we discovered nuclear receptor superfamily 6 group member 1 (NR6A1/GCNF/RTR) is a novel, critical regulator of mammalian NCC specification, formation and survival. Nr6a1 expression in mouse embryos spatiotemporally overlaps with early NCC development. NR6A1 loss-of-function perturbs anterior cranial NCC formation and survival, with complete agenesis of migratory NCC caudal to the first pharyngeal arch. Using targeted molecular and genomic approaches, we demonstrate that these phenotypes are associated with perturbation of NCC specification and epithelial-mesenchymal transition, and with persistent expression of pluripotency-associated factors. Supporting these observations, in vivo overexpression of Oct4 in gastrulating mouse embryos disrupts NCC specification and formation. Conditional temporal deletion revealed that Nr6a1 is required during mid-late gastrulation, demonstrating that the initiation of murine NCC specification likely occurs during gastrulation - earlier than previously thought, but in close alignment with the established timeline of NCC development in other vertebrate model organisms. These findings also reveal that the gold standard transgenic mouse line, Wnt1-Cre, is unsuitable for studying genetic function during NCC specification and formation. In summary, NR6A1 is essential for mammalian NCC development and may function during gastrulation as a bimodal switch modulating pluripotency-associated factors in the neuroepithelium, while concomitantly activating NCC specifiers and regulators of EMT.