A MicroRNA gene is hosted in an intron of a schizophrenia-susceptibility gene

Schizophrenia (SZ) is a neuropsychiatric disorder that affects about 1% of the adult population. Numerous genes have been implicated in SZ susceptibility. MicroRNAs (miRNA) are small RNA molecules that regulate the translation of mRNAs via interactions with their 3' untranslated regions. Identification of known miRNA targets on all human genes indicated that miRNA-346 targets SZ susceptibility genes listed in the SchizophreniaGene database twice as frequently as expected relative to other genes in the genome. The gene encoding this miRNA, miR-346, is located in intron 2 of the glutamate receptor ionotropic delta I (GRID I) gene, which has been previously implicated in SZ susceptibility. We used quantitative real-time PCR to determine the expression levels of miR-346 and GRID1 using brain RNA samples from the Stanley Array Collection, Stanley Medical Research Institute. Expression of both miR-346 and GRID I is lower in SZ patients than that in normal controls (P = 0.017 and 0.086, respectively). However, the expression of miR-346 and GRID1 is less correlated in SZ patients than in bipolar patients or in normal controls. This study implicates the importance of a miRNA in SZ. (C) 2009 Elsevier B.V. All rights reserved.