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Heritage Of A Deadly Disease Pinpointed With Help From Iceland's Genealogical Database

Date:
June 23, 2008
Source:
Public Library of Science
Summary:
Scientists have used Iceland's genealogical database to trace the ancestors of patients suffering from hereditary cystatin C amyloid angiopathy. Analysis shows that the deadly mutation in the cystatin C gene, L68Q, derives from a common ancestor born roughly 18 generations ago, around 1550AD.
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A collaboration of scientists from Iceland and the United States has used Iceland's genealogical database* to trace the ancestors of patients suffering from hereditary cystatin C amyloid angiopathy (HCCAA). Analysis shows that the deadly mutation in the cystatin C gene, L68Q, derives from a common ancestor born roughly 18 generations ago, around 1550AD. 

This dominantly inherited disease, which is due to a mutation in cystatin C (L68Q), strikes young adults with healthy blood pressure. The disease results in death from repeated brain haemorrhages, on average by the age of 30. The origin of the mutation causing HCCAA was previously unknown, but using DNA haplotype analysis* the scientists have shed light on the history of this autosomal dominant disease that has high penetrance in contemporary Icelanders.

The scientists found that 200 years ago, obligate carriers of the mutation lived a normal life span compared to the control population (their spouses). In carriers born around 1820, however, a trend of shortening life span began, resulting in an average life span of only 30 years in people born around 1900. This 30-year lifespan has stayed constant since then in both men and women.

At the same time, a matrilinear effect appeared whereby those who inherited the mutation from the mother died earlier. For carriers born after 1900, the difference is a loss of 9.4 years for those who inherited the mutation from their mothers rather than their fathers. Based on this information, the authors propose that the traditional diet of the nation (which in the past consisted largely of whey-preserved offal as well as meat, dried fish, and butter) "protected" the mutation carriers for almost 300 years until the Icelandic diet changed early in the early 19th century, exemplified by drastic increases in imported carbohydrates and salt.

This finding has implications for studies of Alzheimer's disease as cerebral amyloid angiopathy (CAA) is almost universally found in Alzheimer's patients and normal cystatin C protein is one of the proteins found in amyloid in brains of Alzheimer's patients. Studies are underway to try to elucidate the risk factors with the hope of providing a preventive stategy for cystatin L68Q carriers.

*By deCODE Genetics


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The above post is reprinted from materials provided by Public Library of Science. Note: Materials may be edited for content and length.


Journal Reference:

  1. Palsdottir A, Helgason A, Palsson S, Bjornsson HT, Bragason BT, et al. A Drastic Reduction in the Life Span of Cystatin C L68Q Carriers Due to Life-Style Changes during the Last Two Centuries. PLoS Genet, 4(6): e1000099 DOI: 10.1371/journal.pgen.1000099

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Public Library of Science. "Heritage Of A Deadly Disease Pinpointed With Help From Iceland's Genealogical Database." ScienceDaily. ScienceDaily, 23 June 2008. <www.sciencedaily.com/releases/2008/06/080619203249.htm>.
Public Library of Science. (2008, June 23). Heritage Of A Deadly Disease Pinpointed With Help From Iceland's Genealogical Database. ScienceDaily. Retrieved July 29, 2015 from www.sciencedaily.com/releases/2008/06/080619203249.htm
Public Library of Science. "Heritage Of A Deadly Disease Pinpointed With Help From Iceland's Genealogical Database." ScienceDaily. www.sciencedaily.com/releases/2008/06/080619203249.htm (accessed July 29, 2015).

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