Early transcription factor that plays a key role in somitogenesis, paraxial mesoderm development and regulation of stem cell pluripotency. Essential for the mesenchymal to epithelial transition associated with somite formation. Required for somite morphogenesis, thereby regulating patterning of the axial skeleton and skeletal muscles. Also plays a key role in regulation of stem cell pluripotency. Promotes pluripotency exit of embryonic stem cells (ESCs) by priming ESCs for differentiation. Acts as a key regulator of self-renewal of hematopoietic stem cells (HSCs) by mediating HSCs quiescence and long-term self-renewal. Acts by forming a heterodimer with another helix-loop-helix (bHLH) protein, that binds DNA on E-box motifs (5'-CANNTG-3') and activates transcription of target genes. Heterodimer; efficient DNA binding requires dimerization with another bHLH protein. First detected in a subpopulation of cells lateral to the primitive streak corresponding with the area of prospective segmental plate mesoderm and somites (PubMed:9187085, PubMed:9281340). Later in development, it is expressed throughout the segmental plate and newly formed somites and is restricted to the paraxial mesoderm (PubMed:9187085, PubMed:9281340). After somite formation, its expression decline in the lateral region of the somite (PubMed:9187085, PubMed:9281340). Later it is expressed at highest levels at the cranial and caudal edges of the more mature somites (PubMed:9187085, PubMed:9281340). As the dermomyotome and sclerotome formed, expression disappeared from the ventral regions of the somite, but persisted in the dermomyotome (PubMed:9187085, PubMed:9281340). When the dermomyotome developed further into the dermatome and myotome, expression is detected in both compartments, although more prominently in the dermatome (PubMed:9187085, PubMed:9281340). Expression was also detected in migrating precursors of tongue muscle and in the limb buds (PubMed:9187085, PubMed:9281340). Surface ectoderm and neural tube are the sources of inductive signals required for gene expression and for somite formation.