SIX1 and hearing loss disorder: Mutations in human SIX1 and SIX2 have been associated with multiple congenital disorders such as branchio-oto-renal syndrome (BOR), renal dysplasia, hearing loss, and frontonasal dysplasia syndrome (Ruf et al., 2004; Kochhar et al., 2008; Weber et al., 2008; Mosrati et al., 2011; Guan et al., 2016; Hufnagel et al., 2016).