The muscle segment homeobox (MSX1) gene plays a crucial role in epithelial-mesenchymal tissue interactions in craniofacial development. It plays a regulative role in cellular proliferation, differentiation and cell death. The human MSX1 domain was also found in cow (Bt 302906), mouse (Mm 123311), rat (Rn13592001), chicken (Gg 170873) and clawed toad (XI 547690). Cleft lip and palate is the most common anomaly of the facial part of the skull. The etiology is not fully understood, but it is believed that the key role is played by the genetic factor activated by environmental factors. Among the candidate genes whose mutations could lead to formation of the cleft, the MSX1 homeobox gene is mentioned. Mutations in the gene MSX1 can lead to isolated cleft deformities, but also cause other dismorphic changes. Among the most frequently mentioned is loss of permanent tooth buds (mostly of less than 4 teeth - hypodontia, including second premolars). Mutations of MSX1 are observed in the Pierre- Robin sequence, which may be one of the features of congenital defects or is observed as an isolated defect. Mutation of the gene can lead to the occurrence of a rare congenital defect Wiktop (dental-nail) syndrome. Deletion of a fragment MSX1 (4p16.3) located in the WHS critical region, may be a cause of some symptoms of Wolf-Hirschhorn syndrome.