Journal Article

Molecular and Clinical Correlations in Spinocerebellar Ataxia 2: A Study of 32 Families

Géraldine Cancel, Alexandra Dürr, Olivier Didierjean, Georges Imbert, Katrin Bürk, Agnès Lezin, Samir Belal, Ali Benomar, Myriem Abada-Bendib, Christophe Vial, João Guimarães, Hervé Chneiweiss, Giovanni Stevanin, Gael Yvert, Nacer Abbas, Frédéric Saudou, Anne-Sophie Lebre, Mohamed Yahyaoui, Fayçal Hentati, Jean-Claude Vernant, Thomas Klockgether, Jean-Louis Mandel, Yves Agid and Alexis Brice

in Human Molecular Genetics

Volume 6, issue 5, pages 709-715
Published in print May 1997 | ISSN: 0964-6906
Published online May 1997 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/6.5.709
Molecular and Clinical Correlations in Spinocerebellar Ataxia 2: A Study of 32 Families

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Spinocerebellar ataxia 2 (SCA2) is caused by the expansion of an unstable CAG repeat encoding a polyglutamine tract. One hundred and eighty four index patients with autosomal dominant cerebellar ataxia type I were screened for this mutation. We found expansion in 109 patients from 30 families of different geographical origins (15%) and in two isolated cases with no known family histories (2%). The SCA2 chromosomes contained from 34 to 57 repeats and consisted of a pure stretch of CAG, whereas all tested normal chromosomes (14–31 repeats), except one with 14 repeats, were interrupted by 1–3 repeats of CAA. As in other diseases caused by unstable mutations, a strong negative correlation was observed between the age at onset and the size of the CAG repeat (r = −0.81). The frequency of several clinical signs such as myoclonus, dystonia and myokymia increased with the number of CAG repeats whereas the frequency of others was related to disease duration. The CAG repeat was highly unstable during transmission with variations ranging from −8 to +12, and a mean increase of +2.2, but there was no significant difference according to the parental sex. This instability was confirmed by degree of gonadal mosaicism A of one patient.

Journal Article.  4888 words.  Illustrated.

Subjects: Genetics and Genomics

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