Genes associated with long life

RESEARCHERS AT Beth Israel Deaconess Medical Centre, Children's Hospital Boston and other institutions have pinpointed a region on human Chromosome 4 that is likely to contain a gene or genes associated with extraordinary life expectancy.

Their findings reported in the Proceedings of the National Academy of Sciences, may lead to a better understanding of the aging process. `This is the first study to use humans to try to find genes that play a role in life span,' said Thomas Perls one of the study's co-authors, a geriatrician at Beth Israel Deaconess and Director of the New England Centenarian Study. Louis M. Kunkel, genome-wide scans on 137 sets of two or more exceptionally long-lived siblings in the study,' We have known that only a few genes influence longevity in lower organisms and that now appears to be true in humans.''

The prevalent belief among researchers in the field of ageing research has been that as many as 1,000 genes influence aging. Kunkel and colleagues in the Division of Genetics at Children's Hospital Boston were able to pinpoint a region on Chromosome 4 in humans containing one, or at most, a few longevity-related genes by looking at the trait of exceptional longevity, rather than genes responsible for age-related diseases. Having found the region in which this gene or genes lie, the group intends to identify the exact gene or genes responsible for longevity. Scientists have long wondered what enabled centenarians to maintain good health for so long.

The study authors hypothesise that centenarians have a history of aging very slowly and either markedly delay age-related diseases such as cardiovascular disease, stroke, diabetes, cancer and Alzheimer's disease or avoid them altogether.

The researchers sought the characteristics to explain the disease- resistance and survival advantage characteristic of a group of individuals age 98 and older. Because centenarians are hard to find, they opened their search globally. In the process of taking medical histories it was discovered that many of the subjects also had long-lived siblings.

In a previously published study by Perls, the centenarians' brothers and sisters had a four times greater chance of living to age 91 compared to siblings of a control group.

DNA was extracted from whole blood obtained from 137 so-called sibships centenarians and one or more siblings (ages 91 to 109 years) for a total of 308 people predominantly of European descent.

Co-authors Kunkel and Puca, then performed a sibling pair linkage study, using 400 markers spread along the entire human genome to find any region their subjects had in common.

The search led them to a region on Chromosome 4 that contains between 100 to 500 genes. They are 95 percent certain that area is the right place to search for specific genes that are in part responsible for exceptional longevity.

Once those genes are uncovered, scientists would like to understand the biochemical pathways the gene or genes affect to promote longevity.

The authors speculate that such insight could lead to the development of drugs that mimic what centenarians possess genetically to escape the adverse consequences of ageing.

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