The genetic basis of normal and abnormal craniofacial development

In recent years our knowledge of the genetic mechanisms behind animal development has increased exponentially, and it has become apparent that these mechanisms have been conserved to an astonishing extent during evolution. In this review some important groups of developmental regulatory genes are introduced, and their roles are discussed in the context of craniofacial morphogenesis. Transcription factors regulating both the identity and patterning of embryonic structures and the development of individual organs are often called master regulatory genes. These genes, as well as other transcription factors, are parts of signaling networks mediating cellular communication, including inductive interactions between nearby tissues. Experimental studies, in particular the genetic analysis of mouse development, continue to demonstrate important roles for increasing numbers of these developmental regulatory molecules, including the actual signals, their receptors, and transcription factors in the development of the jaws, cranial bones, and teeth. Molecular genetic studies have shown that mutations in the genes of the signaling networks cause a variety of human craniofacial defects.