IRX1 and North Carolina macular dystrophy: For example, North Carolina macular dystrophy (NCMD) has been linked to non-coding single-nucleotide variants (SNVs) within DNase I hypersensitive sites upstream of the PRDM13 gene and several independent duplication events encompassing this site on chromosome 6 (MCDR1) or another DNase I hypersensitive site near the IRX1 locus on chromosome 5 (MCDR3) [9, 34] (Figure 2).