Analysis of spinocerebellar ataxia type 2 gene and haplotype analysis: (CCG) 1-2 polymorphism and contribution to founder effect

Kazuyuki Mizushima, Mitsunori Watanabe, Ikuko Kondo, Koichi Okamoto, Masami Shizuka, Koji Abe, Masashi Aoki, Mikio Shoji

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12 Citations (Scopus)

Abstract

Spinocerebellar ataxia type 2 is a familial spinocerebellar ataxia with autosomal dominant inheritance. The gene responsible was recently cloned and this disorder was found to be the result of a CAG expansion in its open reading frame. We analysed 13 SCA2 patients in seven unrelated families in Gunma Prefecture, Japan. In four of the seven families, we detected CCG or CCGCCG interruptions in only the expanded alleles. Cosegregation of these polymorphisms with SCA2 patients was established within each family. Together with the results of haplotype analyses, we considered that at least two founders were present in our area and that these (CCG) 1-2 polymorphisms may make analysis of founder effects easier. By sequencing analysis we found that although the number of the long CAG repeat varied in each subclone of expanded alleles, these polymorphisms did not change their configuration. This finding suggests that CCG or CCGCCG sequences are stable when surrounded by the long CAG repeat and a single CAG. Moreover, the presence of these polymorphisms may lead to miscounting the repeat size by conventional estimation using a size marker such as an M13 sequencing ladder. Therefore we should consider these polymorphisms and accurately determine the repeat size by sequencing.

Original languageEnglish
Pages (from-to)112-114
Number of pages3
JournalJournal of medical genetics
Volume36
Issue number2
Publication statusPublished - 1999 Mar 8

Keywords

  • CCG repeat polymorphism
  • Founder effect
  • Spinocerebellar ataxia type 2

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

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    Mizushima, K., Watanabe, M., Kondo, I., Okamoto, K., Shizuka, M., Abe, K., Aoki, M., & Shoji, M. (1999). Analysis of spinocerebellar ataxia type 2 gene and haplotype analysis: (CCG) 1-2 polymorphism and contribution to founder effect. Journal of medical genetics, 36(2), 112-114.