Myogenin belongs to a family of myogenic transcription factors, including MyoD, myf5, and MRF4, which are critical in muscle development. Myogenic factors are transcription factors consisting of an amino acid-rich region and a helix-loop-helix (HLH) structure, which can promote muscle development and maintain muscle-specific gene expression by transactivation. Myogenin plays a key role in determining the commitment and differentiation of primitive mesenchymal cells into skeletal muscle. Myogenin is found strictly in cells of skeletal muscle origin, and is therefore used as a biomarker for tumors of the muscle lineage, including alveolar rhabdomyosarcomas. Anti-Myogenin staining may occur in Wilms' tumor, and labels the nuclei of myoblasts in developing muscle tissue. It is also expressed in some leiomyosarcomas.