Twist is a basic helix-loop-helix (b-HLH) transcription factor that functions as a master regulator of embryonic morphogenesis and plays essential roles in mesenchymal differentiation and osteogenic determination. Mutations affecting the b-HLH domain of the Twist gene have been associated with Saethre-Chotzen syndrome, an autosomal dominant craniosynostosis disorder causing craniofacial and limb abnormalities. Twist is expressed throughout the epithelial somite but not in the myotome. Twist requires dimerization with the E proteins and inhibits myogenic regulatory factors. It has been implicated as regulator of the temporal and spatial formation of myotomes.
