Craniofacial disorders caused by mutations in homeobox genes MSX1 and MSX2

The molecular biology of the homeobox genes MSX1 and MSX2 is reviewed. In a selective type of tooth agenesis, an MSX1 G-->C transversion results in a missense mutation Arg31Pro. The phenotype is due to haploinsufficiency. Bos ton-type craniosynostosis involves an MSX2 C-->A transversion, resulting in a missense mutation Pro7His. Three different mutations on MSX2 cause parie tal foramina by haploinsufficiency. These mutations, which result in decrea sed parietal ossification, are in marked contrast to the gain-of-function m utation for Boston-type craniosynostosis, which results in increased sutura l ossification.