Misregulation of TWIST1 dimerization with HAND2 is caused by mutations of phosphoresidues in the PKA consensus domain or in the bHLH domain, which have been reported to be associated with Saethre-Chotzen syndrome (Firulli et al., 2005; El Ghouzzi et al., 1997). Here, TWIST1 is linked to Saethre-Chotzen syndrome.