PAX6 and isolated aniridia: Heterozygous null mutations within PAX6, cytogenetic deletions of chromosome 11p13 that encompass PAX6 or chromosomal rearrangements that prevent PAX6 expression from one allele are all causal for aniridia (Ton et al., 1991; Fantes et al., 1995; Lauderdale et al., 2000; van Heyningen and Williamson, 2002; Robinson et al., 2008).