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Archiver > GENEALOGY-DNA > 2007-07 > 1185365854


From:
Subject: Re: [DNA] Is H5a a pathological subclade?
Date: Wed, 25 Jul 2007 08:17:34 EDT


In a message dated 7/24/2007 9:23:05 PM Pacific Daylight Time,
writes:

> _http://www.mitomap.org/rimtab3.html_ (http://www.mitomap.org/rimtab3.html)
>
> lists the "Clinical Phenotypes (non-LHON)
> Associated with mtDNA rRNA and tRNA
> Mutations Reported in the Literature."
> According to this list Organized by Phenotype:
> rRNA/tRNA Mutations, T4336C in the coding
> region can be considered pathologic and is associated
> with Alzheimer's, Parkinson's Disease, deafness and migraine.
> This is considered "confirmed by multiple reports in the literature".

This is curious -- that mutation is listed in a different section with a
status of "unclear."

http://www.mitomap.org/cgi-bin/tbl9gen.pl

The above URL has more references than the page you found. Judging by the
titles/abstracts, some of the earliest reports have not been confirmed. Here's
one of the counter-examples:

=====

J Med Genet. 1996 Dec;33(12):1002-6.

The tRNA(Gln) 4336 mitochondrial DNA variant is not a high penetrance
mutation which predisposes to dementia before the age of 75 years.

Tysoe C, Robinson D, Brayne C, Dening T, Paykel ES, Huppert FA, Rubinsztein
DC.

East Anglian Regional Genetics Service, Addenbrooke's NHS Trust, Cambridge,
UK.

The genetic factors that predispose to Alzheimer's disease (AD) are
heterogeneous. Two recent reports have suggested that a mitochondrial DNA mutation
within the tRNAGln gene, located at position 4336, may be a risk factor for AD, as
it was found in 10/256 (3.9%) cases with AD confirmed by necropsy. Although
low prevalences of this mutation were detected in non-demented subjects in both
of these studies, the controls were not carefully matched with the AD cases.
We have investigated the frequency of this mutation in two community based
elderly cohorts in Cambridgeshire, who have participated in longitudinal studies
of cognitive function. The 4336 mitochondrial mutation was detected in 8/ 443
people examined. These people were found to be non-demented at ages 74, 81,
84, 86, 89, 90, 91, and 102 years, in contrast to the previously described cases
whose onset of dementia occurred between 60 and 76 years (mean 68).
Accordingly, we believe that this mitochondrial variant is not a high penetrance
mutation which predisposes to dementia before the age of 76 years.

Publication Types: Research Support, Non-U.S. Gov't

PMID: 9004131 [PubMed - indexed for MEDLINE]

=====

Ann Turner







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