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Spinocerebellar ataxia type 17 associated with an expansion of 42 glutamine residues in TATA-box binding protein gene
  1. D Nolte1,
  2. E Sobanski2,
  3. A Wißen1,3,
  4. J U Regula4,
  5. C Lichy4,
  6. U Müller1
  1. 1Institut für Humangenetik, Justus-Liebig Universität Giessen, Germany
  2. 2Zentralinstitut für Seelische Gesundheit, Mannheim, Germany
  3. 3Klinik für Augenheilkunde, Universitätsklinikum Schleswig-Holstein Campus Kiel, Germany
  4. 4Neurologische Klinik, Universitätsklinikum Heidelberg, Germany
  1. Correspondence to Dr Dagmar Nolte, Institut für Humangenetik, Justus-Liebig Universität Giessen, Schlangenzahl 14, 35392 Giessen, Germany; dagmar.nolte{at}humangenetik.med.uni-giessen.de

Abstract

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.

  • Spinocerebellar ataxia type 17
  • SCA17
  • TBP
  • repeat expansion

https://doi.org/10.1136/jnnp.2009.180711

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    Footnotes

    • Competing interests None.

    • Patient consent Obtained.

    • Provenance and peer review Not commissioned; externally peer reviewed.