Exclusion of expansion of 50 CAG/CTG trinucleotide repeats in bipolar disorder.

OBJECTIVE

The purpose of this study was to identify the specific expanded CAG/CTG trinucleotide repeat associated with bipolar disorder.

METHOD

The study employed an efficient multistage approach for using a genomic CAG/CTG screening set.

RESULTS

The authors found no evidence of expanded repeats at 43 polymorphic autosomal loci and seven X chromosomal loci. Secondary screening was pursued at the only locus that contained a large allele (37 repeats) in the primary screening. No association was found between allele size and diagnostic status.

CONCLUSIONS

It is highly unlikely that expansions in repeat size at any of the 50 candidate trinucleotide repeat loci examined are responsible for the association between expanded CAG/ CTG repeats and bipolar disorder. However, although the authors prioritized the repeats that were a priori most likely to be involved, the study does not reject the more general hypothesis that expanded CAG/CTG repeats are implicated in the pathogenesis of bipolar disorder.