FBXL5 and Turner syndrome: Our observation of loss of DNA methylation at the FBXL5, SCMH1 and CACYBP promoters in 45, X females compared to XX females and XY males, but to a lesser degree than in males with KDM5C mutations, supports this hypothesis and suggests that deregulation of epigenetic targets of KDM5C could be relevant to the mild neurodevelopmental impairments found in females with Turner syndrome.