Repeat sizes at CAG/CTG loci CTG18.1, ERDA1 and TGC13-7a in schizophrenia.

A number of studies using the repeat expansion detection (RED) technique have suggested an association between unknown large CAG / CTG repeats and schizophrenia. The polymorphic CAG / CTG repeat loci CTG18.1 and ERDA1 have been reported to account for a high proportion (similar to 90%) of the large repeats detected by RED and may therefore be responsible for the cited association. The recently described locus TGC13-7a contains a highly polymorphic CTA/TAG and CAG / CTG composite repeat, and is thus another authentic candidate. In the present investigation, each locus was analysed for association with schizophrenia in a sample of 206 patients and 219 group-matched controls. No evidence for association of CTG18.1, ERDA1 and/or TGC13-7a with schizophrenia was found. The combined data accounted for only 54% of the CAG / CTG arrays of > 40 repeats found in our previous RED analysis. Psychiatr Genet 10:33-37 (C) 2000 Lippincott Williams & Wilkins.