Loss of function mutations in the bHLH domain in one allele of the TWIST1 gene cause Saethre-Chotzen Syndrome (SCS) in humans, an autosomal dominant craniofacial disease caused by gene haploinsufficiency [18-20], denoting the functional importance of the TWIST1 bHLH domain. Here, TWIST1 is linked to Saethre-Chotzen syndrome.