SOX9 and campomelic dysplasia: Given the phenotypic overlap between craniofacial abnormalities of campomelic dysplasia and PRS, it had been long speculated, but not formally demonstrated, that regulatory elements harbored by the PRS region deletions might regulate SOX9 (Amarillo et al., 2013; Benko et al., 2009; Gordon et al., 2009, 2014).