Furthermore, sox9a mutant zebrafish embryos exhibit craniofacial and cartilage developmental defects analogous to human campomelic dysplasia, which is caused by SOX9 haploinsufficiency, highlighting the conservation of SOX9 function across vertebrate facial formation (Wagner et al., 1994; Yan et al., 2002, 2005). Here, SOX9 is linked to campomelic dysplasia.