How do you live to be 100?

Simon Bishop comments on the newly-discovered longevity gene

THIS week I read a headline that caught my eye: ‘Scientists identify gene that can help you live to 100.’ Now that, I decided, sounds interesting. I wouldn’t mind a gene like that.

To many, growing old is a terrifying thing. To others it commands respect and comes with the benefits of experience. But to live to 100, even with modern longer life spans… now that would be an achievement indeed. I could travel the world, I could learn all that there is to know and witness history in the making, all in time for my telegram from the Queen. So tell me, what is this gene?

The gene to which the article refers is called telomerase. But wait! This is not a newly discovered gene! Elizabeth Blackburn, Carol Greider and Jack Szostak won this year’s Nobel Prize in Physiology or Medicine for their work on telomerase, and their first hint at its existence occurred on Christmas Day, 1984. Everybody has it. It is biologically impossible for different people to have different numbers of genes, so it cannot be that some people have it and others don’t. All humans have the same complement of genes – around 20–30,000 – because they are all needed to make you function and be what you are. Take note: it is not possible that they have a gene that you don’t. But if everybody has it, why don’t we all live to 100?

First, we need to understand what telomerase is. Every time the cells in your body divide, your DNA must be duplicated also. But the enzymes that assemble new DNA cannot replicate your genes with 100 per cent accuracy. A short starting fragment, which is needed to set the enzymes to work, is always lost, and with each replication your DNA gets ever so slightly shorter and disrupted. Shortening of DNA ends, or telomeres, correlates with ageing. Telomerase adds this short fragment back onto telomeres. It keeps you bright and youthful and without it the very processes that maintain our bodies would also be our undoing.

Recently, Yousin Suh and colleagues at the Albert Einstein College of Medicine in New York compared the genes of centenarian Ashkenazi Jews with those of the spouses of the centenarian’s children, in doing so examining a close-knit community but without the possibility of inheritance, and discovered something subtler than a new gene.

Every gene in your body (except those on your X or Y chromosomes) comes as one of a pair. These two versions of the same gene can be different, sometimes radically so, and often one is dominant over the other. These gene versions, or alleles, come from a pool of many different varieties throughout the entire population. Allele is a word you won’t often read in a newspaper, and I thank Redbrick for letting me use it, but its meaning is very important. Centenarians – Ashkenazi Jews in this example – do not have a gene that you don’t: they simply have an allele of telomerase that makes the enzyme work more efficiently. This variation allows better maintenance of telomeres and confers healthy ageing and exceptional longevity in humans.

Am I being pedantic? Am I being a stickler for accuracy in scientific terminology? I would argue that we benefit from pedantry in this case. If 100 year olds have a gene that we don’t, then we can wave goodbye to that telegram. But if they have a more efficient version of a gene that we also have, then the key for research is to boost the efficiency of what we mere mortals already have. It’s about tweaking the tools at hand, not reinventing the wheel.

If they get it right, what would you do with your time?