Mesodermal transcription factor that plays a key role in somitogenesis and is specifically required for sclerotome development. Required for maintenance of the sclerotome polarity and formation of the cranio-cervical joints. Binds specifically to the promoter of target genes and regulates their expression. Required for hematopoietic stem cell (HSCs) induction via its role in somitogenesis: specification of HSCs occurs via the deployment of a specific endothelial precursor population, which arises within a sub-compartment of the somite named endotome. Acts by mediating specification of endothelial cells of the endotome within the nascent somite, notably by repressing expression of cxcl12b. Localizes predominantly in the nucleus. Expressed within the early somite and then becomes restricted to the external cell layer (ECL) and consequently to appendicular muscle populations. Defects in somite lineages. Secondary trunk myogenesis is reduced, as well as appendicular and hypaxial muscles and their progenitors. These cell types derive from the external cell layer (ECL) and ECL cell numbers are reduced. The endotome is expanded at the expense of a second somitic cell type. The resulting increase in endotome-derived cells that migrate to colonize the dorsal aorta generates a dramatic increase in chemokine-dependent hematopoietic stem cell (HSCs) induction.