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Diseases

Genetic and Rare Diseases Information Center (GARD)

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Spinocerebellar ataxia 2


Other Names for this Disease

  • Olivopontocerebellar atrophy 2
  • Olivopontocerebellar atrophy Holguin type
  • SCA 2
  • SDSEM
  • Spinocerebellar ataxia Cuban type
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Inheritance

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How is spinocerebellar ataxia 2 inherited?

Spinocerebellar ataxia 2 (SCA2) is inherited in an autosomal dominant manner. This means that having one changed (mutated) copy of ATXN2 (the responsible gene) in each cell is enough to cause signs and symptoms of the condition.

The ATXN2 gene mutations that cause SCA2 involve a DNA sequence called a 'CAG trinucleotide repeat.' It is made up of a series of three DNA building blocks (CAG stands for cytosine, adenine, and guanine) that appear multiple times in a row. The CAG sequence is normally repeated about 22 times in the gene, but it can be repeated up to 31 times without causing health problems. SCA2 develops in people who have 32 or more CAG repeats in the ATXN2 gene.

In most cases, an affected person inherits the mutated gene (with too many repeats) from an affected parent. However, in some cases, an affected person does not have an affected parent. People with an increased number of CAG repeats who don't develop SCA2 are still at risk of having children who will develop the disorder. This is because as the gene is passed down from parent to child, the number of CAG repeats often increases. In general, the more repeats a person has, the earlier symptoms begin. This phenomenon is called anticipation. People with 32 or 33 repeats tend to develop symptoms in late adulthood, while people with more than 45 repeats often have symptoms by their teens.  For some reason, the number of repeats tend to increase more when the gene is inherited from a person's father than when inherited from a person's mother.[1] Each child of an affected person has a 50% chance of inheriting the CAG repeat expansion.
Last updated: 6/24/2014

References
  1. Spinocerebellar ataxia type 2. Genetics Home Reference. February, 2011; http://ghr.nlm.nih.gov/condition/spinocerebellar-ataxia-type-2. Accessed 6/23/2014.


Other Names for this Disease
  • Olivopontocerebellar atrophy 2
  • Olivopontocerebellar atrophy Holguin type
  • SCA 2
  • SDSEM
  • Spinocerebellar ataxia Cuban type
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.