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Archiver > GENEALOGY-DNA > 2007-07 > 1185501946


From: "Dora Smith" <>
Subject: Re: [DNA] Is H5a a pathological subclade?
Date: Thu, 26 Jul 2007 21:05:46 -0500
References: <cb1.1666ab77.33d8995e@aol.com>


In plain English, they're saying that this is a gene that causes Alzheimers,
but it doesn't often actually cause Alzheimers. A gene with incomplete
penetrance usually needs additional factors to cause the condition; other
genes, individual metabolic differences, or environment and lifestyle. I
read that that sort of thing is true of alot of mtdna mutations for health
problems.

Yours,
Dora Smith
Austin, TX


----- Original Message -----
From: <>
To: <>
Sent: Wednesday, July 25, 2007 7:17 AM
Subject: Re: [DNA] Is H5a a pathological subclade?


> 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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