Growth and development of the craniofacial skeleton is under genetic control and modified by environmental factors. This growth control system mediates the specialization and enlargement of craniofacial skeletal tissue in concert with the specialization and enlargement of the tissues supporting neural activity, respiration, mastication, and deglutition. Craniofacial development is controlled by complex gene-regulatory networks. For example, HOX and DLX genes are responsible for patterning of the vertebrate head in rostro-caudal and dorso-ventral axes, respectively . Other key genes expressing transcription control factors and growth factors are responsible for mediating the growth, development, and maintenance of skeletal and soft tissues throughout embryogenesis and postnatal development .