A non-coding mutation implicates HCFC1 in non-syndromic intellectual disability

Human disease mutation discovery has so far been biased towards protein coding regions. Having excluded all annotated coding regions, we performed targeted massively parallel re-sequencing of the non-repetitive genomic linkage interval of the MRX3 family at Xq28. We identified a regulatory mutation in the YY1 transcription factor binding site, which leads to overexpression of the chromatin-associated transcriptional regulator, HCFC1. When tested on embryonic murine neural stem cells (NSCs) and embryonic hippocampal neurons, HCFC1 overexpression led to a significant increase of the production of astrocytes and considerable reduction in neurite growth. Two other non-synonymous, potentially deleterious changes have been identified by X-exome sequencing in individuals with intellectual disability, implicating HCFC1 in normal brain function. Total RNA was extracted from LCL derived from four unrelated male controls, five unrelated female controls and two affected male cousins from the MRX3 family.