A neurological disease caused by an expanded CAG trinucleotide repeat in the TATA-binding protein gene: a new polyglutamine disease?

To investigate whether the expansion of CAG repeats of the TATA-binding protein (TBP) gene is involved in the pathogenesis of neurodegenerative diseases, we have screened 118 patients with various forms of neurological disease and identified a sporadic-onset patient with unique neurologic symptoms consisting of ataxia and intellectual deterioration associated with de novo expansion of the CAG repeat of the TBP gene. The mutant TBP with an expanded polyglutamine stretch (63 glutamines) was demonstrated to be expressed in lymphoblastoid cell lines at a level comparable with that of wild-type TBP. The CAG repeat of the TBP gene consists of impure CAG repeat and the de novo expansion involves partial duplication of the CAG repeat. The present study provides new insights into sporadic-onset trinucleotide repeat diseases that involve de novo CAG repeat expansion.