A defect in the ionotropic glutamate receptor 6 gene (GRIK2) causes autosomal recessive mental retardation

Non-syndromic mental retardation is one of the most important unresolved problems in genetic health care. Autosomal forms are far more common than X-linked ones, but in contrast to the latter, they are still largely unexplored. Here we report on a complex mutation in the ionotropic glutamate receptor 6 gene (GRIK2, GLUR6), which co-segregates with moderate to severe non-syndromic autosomal recessive mental retardation in a large consanguineous Iranian family1. The predicted gene product lacks the first ligand-binding domain, the two adjacent transmembrane domains and the putative pore-forming loop of the GLUK6 protein, suggesting a complete loss of function, which is supported by electrophysiological data. This finding provides the first irrefutable proof that GLUK6 is indispensable for higher brain functions in man, and future studies of this and other ionotropic kainate receptors will shed more light on the pathophysiology of mental retardation. Keywords: array CGH Five samples with a homozygous deletion of GLUR6 were analysed by means of submegabase array CGH on platform GPL5114