Analysis of CAG/CTG repeat size in Chinese subjects with schizophrenia and bipolar affective disorder using the repeat expansion detection method

Abstract Background: Family studies of schizophrenia and bipolar affective disorder provide evidence for genetic anticipation, which (in common with a number of mendelian disorders), may be caused by triplet repeat expansion. This hypothesis is strengthened by evidence from repeat expansion detection (RED) analysis revealing association between the psychoses and long CAG/CTG trinucleotide repeats. Methods: We performed RED on Han Chinese subjects with schizophrenia (82), bipolar affective disorder (43), and normal controls (61), using a CTG 10 oligonucleotide. Results: Comparison between cases and controls revealed no significant association between long repeats and affected status. We also found no detectable association with age at onset and repeat length in either bipolar affective disorder or schizophrenia. Overall, the size distribution of CAG/CTG repeats in Chinese subjects was not significantly different from those reported previously for Caucasian subjects. Conclusions: These findings indicate that CAG/CTG repeat expansion is not likely to be a major etiological factor for psychosis in Chinese populations.