Mutations in the guanine nucleotide exchange factor gene IQSEC2 cause nonsyndromic intellectual disability

Cheryl Shoubridge and Jozef Gecz and colleagues report the identification of mutations in IQSEC2, a guanine nucleotide exchange factor for ARF GTPases, in individuals with non-syndromic intellectual disability. The first family identified as having a nonsyndromic intellectual disability was mapped in 1988. Here we show that a mutation of IQSEC2, encoding a guanine nucleotide exchange factor for the ADP-ribosylation factor family of small GTPases, caused this disorder. In addition to MRX1, IQSEC2 mutations were identified in three other families with X-linked intellectual disability. This discovery was made possible by systematic and unbiased X chromosome exome resequencing.