Twist1 is crucial in patterning the cranial neural crest cells during frontonasal development

Mutations in TWIST1 are associated with Saethre-Chotzen and Sweeny-Cox syndromes with a range of craniofacial anomalies. In mouse, haploinsufficiency of Twist1 caused mild skull defects whereas Twist1 null embryos died during midgestation due to failure of neural tube closure and aberrant apoptosis of cranial neural crest cells (CNCCs). Tissue-specific inactivation of Twist1 in premigratory CNCCs disrupted epithelial-mesenchymal transition during CNCC delamination. Migrating CNCCs in the Twist1flox/flox; Wnt1-Cre embryos exhibited persistent expression of neuroectodermal markers and neural crest marker Sox10. Additionally, these mutants exhibit failure of activation of ectomesenchyme genes including Alx3 and Alx4. In this study, we aimed to show that Twist1 function is required in postmigratory CNCCs for their survival and ectomesenchymal differentiation. And to understand the role of Twist1 in postmigratory CNCCs patterning during frontonasal development we performed cell sorting from the frontonasal tissues at E9.25 and Bulk RNAseq revealed significant overexpression of the branchial arch marker genes in the frontonasal process of the Twist1 conditional mutant mice embryos.