We also found discrete areas of age-related hypomethylation on chromosome 7 at the transcription start site of Isoc2b, an isochorismatase-like protein, and two sites on the X chromosome near the end of the Mid1 gene, which encodes a microtubule-binding protein important for cell division, and whose overexpression has been implicated in the pathogenesis of Opitz syndrome[58]. Here, MID1 is linked to Opitz G/BBB syndrome.