Probable transcriptional regulator involved in developmental processes. Is required for normal development of the pharyngeal arch arteries. Haploinsufficiency of the TBX1 gene is responsible for most of the physical malformations present in DiGeorge syndrome (DGS) and velocardiofacial syndrome (VCFS). DGS is characterized by the association of several malformations: hypoplastic thymus and parathyroid glands, congenital conotruncal cardiopathy, and a subtle but characteristic facial dysmorphology. VCFS is marked by the association of congenital conotruncal heart defects, cleft palate or velar insufficiency, facial dysmorpholgy and learning difficulties. It is now accepted that these two syndromes represent two forms of clinical expression of the same entity manifesting at different stages of life. Defects in TBX1 are a cause of DiGeorge syndrome (DGS). Defects in TBX1 are a cause of velocardiofacial syndrome (VCFS). Defects in TBX1 are a cause of conotruncal heart malformations (CTHM). CTHM consist of cardiac outflow tract defects, such as tetralogy of Fallot, pulmonary atresia, double-outlet right ventricle, truncus arteriosus communis, and aortic arch anomalies. 3 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.