DNA methylation fingerprint of a KDM5C loss-of-function mutation in patients with intellectual disability

Characterization of methylation changes related do KDM5C c.807delC (p.V271X) Mutations in KDM5C (lysine (K)-specific demethylase 5C) were associated to up to 3% of the X-linked ID cases. Males carrying KDM5C mutations present reduced activity of the KDM5C protein, increasing H3K4 tri-methylation, which ultimately leads to up-regulation of KDM5C target genes. Whole-exome sequencingi n one of three brothers with intellectual disability followed by confirmation by Sanger sequencing in the family identified a frameshift mutation in the KDM5C exon 7 that devoid of the JmjC catalytic domain from the protein. Two other brothers also presenting intellectual disability as well as in their clinically normal mother, who had completely skewed X-inactivation also had the mutation. An empirical Bayesian analysis of methylation levels between cases and controls identified 399 differentially methylated positions, 288 hypomethylated and 111 hypermethylated.Among the genes associated with the hypomethylated CpGs were FBXL5 and CACYBP, both involved in the ubiquitination pathway. Subjects (3 affected brothers and non-affected mother carrying KDM5C mutation) and controls (2 female relatives and 12 male controls) were subjected to sequencing and genome-wide methylation analyses (450K, Illumina)