IRF6 and orofacial cleft: IRF6 disruption is causal for syndromic cleft in Van der Woude and popliteal pterygium syndromes, and associated with non-syndromic orofacial clefts (Zucchero et al., 2004; Leslie et al., 2013; Kondo et al., 2002; Beaty et al., 2016).