Cranial neural crest shortage leads to extensive craniofacial anomalies in mice mutant for the NR2F1/2 nuclear receptors

Nuclear receptors are iteratively deployed during neural crest development, from pre-induction through differentiation stages. NR2F1 and NR2F2 in particular have been proposed as broad regulators of early neural crest gene expression in mammals, but the timing, extent, and redundancy of their developmental requirement has remained unclear, as Nr2f1 and Nr2f2 single mouse mutants present only minimal craniofacial phenotypes. Here we report the dynamic expression patterns of Nr2f1 and Nr2f2 in the mouse cranial neural crest from specification through post-migratory stages. Combined conditional knockout of both Nr2f1 and Nr2f2 in the neural crest with Wnt1-Cre or Pax3Cre caused severe midfacial clefting, loss of the maxilla and palate, and hypoplasticity of all other facial skeletal elements except the distal mandible. These perinatal phenotypes were rooted in a major shortage of pharyngeal arch mesenchyme at mid-gestation. This in turn traced to a deficiency of migrating neural crest cells, first evident in the trailing part of the first arch migratory stream at embryonic day 8.75. RNAseq at a slightly earlier stage revealed downregulation of many migratory neural crest genes, including a possible direct target, the phospholipase Plcg2. These findings reveal a vital requirement for NR2F1/2 within the later-forming cranial neural crest. Overall design: Bulk RNAseq was performed on individual heads cut caudal to the first pharyngeal arch of control and Wnt1-Cre;Nr2f1fl/fl;Nr2f2fl/fl mouse embryos at the 8 somite (±1 somite) and 12 somite (±1 somite) stages. Total of 12 samples, 3 replicates each genotype and stage.