PITX2 and Huntington disease: For example, p.E79K substitution (corresponds to CRX E80) in OTX2 HD is associated with dominant early-onset retinal dystrophy (Vincent et al., 2014), heterozygous p.R89G (corresponds to CRX R90) mutation in OTX2 HD causes severe ocular malformations (Ragge et al., 2005), and missense mutations of the CRX K88 and R90 homologous residues in PITX2 HD are associated with dominant Rieger syndrome (Perveen, 2000).