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Spinocerebellar ataxia type 17 associated with an expansion of 42 glutamine residues in TATA-box binding protein gene

2010; BMJ; Volume: 81; Issue: 12 Linguagem: Inglês

10.1136/jnnp.2009.180711

1468-330X

Dagmar Nolte, Esther Sobanski, A. Wissen, Jens Regula, Christoph Lichy, Ulrich Müller,

DNA Repair Mechanisms

Background Spinocerebellar ataxia type 17 (SCA17) is caused by abnormal expansions of CAG/CAA trinucleotides within the TATA-box binding protein gene ( TBP ). The currently accepted critical threshold of abnormal expansions is ≥43. Objective To investigate the minimal CAG/CAA expansion within the TBP in SCA17. Results 285 patients with autosomal-dominant ataxia were examined, and abnormal or borderline expansions of CAG/CAA within TBP in eight cases were found. Of those, four patients from three families had exactly 42 CAG/CAA trinucleotides, that is, one codon less than the currently accepted critical threshold of 43. The four patients presented with a relatively benign phenotype. All had dysdiadochokinesia and dysarthria. Mild gait ataxia was observed in three of the four patients. Conclusion The reference definition of at least 43 CAG/CAA codons for pathological SCA17 alleles should be lowered to 42.