Re: Genetic Marker for Longevity Found.
Posted by Thermus aquaticus on Feb 17, 2002 at 12:55
(129.59.237.200)Re: Genetic Marker for Longevity Found. (Mike Kremer)
No apology necessary. I would never have suspected you suffer from any form of dyslexia! From reading your posts, it is not obvious to me at all. It was just me being pedantic.
With regard to the genetics, you obviously have some understanding of the issue, but I think you are trying to compare apples with oranges.
Telomeres aren’t really anything to do with the aging process. Telomeres protect chromosome ends from degradation and rearrangement and from being recognized as DNA breaks. Telomeres consist of a variable number of tandem simple repeated DNA sequences. Telomeres on the ends of chromosomes are not completely reproduced during cell division, so the average telomere length in the cells of an organism shortens as the organism grows older. The exception to this is in the germ cells of our testes. These cells contain the telomerase enzyme that maintains telomere length, and ensures that our gametes (and thus, our children) start off with the full telomere complement. Thus, telomere length in our somatic tissue (ie. anything other than the germ cells) is an indicator of approximate age, although not necessarily the cause of aging itself.
Telomeres do serve an important cellular function. Mice that are deficient in telomerase function display genomic instability, cell death and cancer progression, but only after 5 or 6 generations of inbreeding. In other words, a telomerase-deficient mouse is normal despite its reduced telomere length. It takes 6 rounds of interbreeding of these mice before telomere lengths are reduced to the point where there is a phenotypic consequence. So, although telomeres reduce with aging, the lengths of telomeres do not reduce to the point where problems occur within the length of one mammalian lifetime.
The study of telomeres is important with regard to cancer, however. Nearly all cancerous cells, regardless of their origin, have acquired telomerase function. This is an essential requirement for cancer progression because the greatly increased proliferation rate of cancer cells would quickly reduce their telomere lengths to the point where the cell dies. So, blocking telomerase function in cancer cells is one avenue for new potential cancer treatments.
The aging process, on the other hand, is thought to be the result of the accumulation of mitochondrial gene mutations (affecting the ability to metabolize and produce and store energy) and a genome-wide down-regulation of tissue maintenance genes (affecting the structural integrity of the whole body).
So, your statement…
Genetic markers for longevity are more likely to be found in persons that live above average life span…is quite correct. The mutation in the mitochondrial gene in question might counteract the natural degradation of mitochondrial function over time. But your references to telomeres are a bit of a non-sequitor in the context of this news story.
Am I making any sense?
Follow Ups:
- Re: Genetic Marker for Longevity Found. Mike Kremer 17/2 17:29 (0)