Molecular interpretation of expanded RED products in bipolar disorder by CAG/CTG repeats located at chromosomes 17q and 18q

Previously we provided evidence that the anticipation observed in bipolar ( BP) disorder may be explained by expanded CAG/CTG triplet repeats. Data wer e generated with the repeat expansion detection (RED) method in a BP case-c ontrol sample showing a significant association of BP disorder with expande d CAG/CTG repeats (RED products of 120 bp). In this study we demonstrated t hat 86% of the RED expansions could be accounted for by the ERDA1 and CTG18 .1 CAG/CTG repeats located respectively on chromosomes 17 and 18. Further, significantly different allele distributions were observed for ERDA1, with a larger proportion of BP patients (34.7%) carrying one or two expanded ERD A1 alleles(CAG/CTG repeats >40) than controls (19.2%) (P = 0.032). Also, a negative correlation was observed for ERDA1 between CAG/CTG length and age at onset in affected offspring of eight BP families. Although interesting, these data should be interpreted with caution since the ERDA1 association d id not remain significant after correcting for multiple testing. Also, no l inkage was observed between BP disorder and expanded ERDA1 alleles, in the families. (C) 1999 Academic Press.