TWIST1 and aniridia: Inversion prone position effects are not only limited to other species, it has also been reported in some human disease conditions, such as aniridia (PAX6), campomelic dysplasia (SOX9), familial adenomatous polyposis (APC) and Saethre-Chotzen syndrome (TWIST1) (Fantes et al., 1995; de Chadarevian et al., 2002; Cai et al., 2003; Velagaleti et al., 2005).