• Question: which gene is responsible for ageing and why can't we regenerate our own body cells?

    Asked by Tegan Rose Allen to Sophie, Matt, Ravinder, Barbara on 8 Mar 2015.
    • Photo: Barbara Shih

      Barbara Shih answered on 8 Mar 2015:

      Aging is quite a big field and I’m afraid I only know random bits and pieces related to it.

      Genes and aging:
      I don’t think there we have found a specific gene responsible for aging in humans. They have found that mutation in a gene (daf-2) can double the lifespan of C. elegans. This gene and its hormone-signally pathway has been found to be evolutionally conserved (i.e. remains similar/unchanged throughout evolution) and is similar to the insulin pathway in mammals.
      http://www.nature.com/scitable/topicpage/genetic-control-of-aging-and-life-span-847

      Cell age:
      Scientists noticed that cells can only divide a certain number of times before they stops dividing. There are these repetitive sequences at the end regions our chromosomes (telomere), which normally helps separating the chromosomes but shorten as with each replication. This is because DNA replication cannot occur all the way to the end. Some cells, such as stem cells, express proteins that replenishes telomeres. Maybe we can extend human life span of we can work out how to deal with the finite number of times cells can divide.

      Physical appearance of aging:
      Our skin physically look older because due to changes in skin structure: loss of fat, loss of certain proteins, and loss of protein organisation. Reasons that could cause that including chemical reactions that occur when your body is exposed to undesirable chemicals/things. For example, smoking and tanning speed up the physical appearance of age. (http://www.nytimes.com/slideshow/2009/02/05/health/agingfaces_well_slideshow_index.html)

      When you say regeneration of our own cells, do you mean making more cells (limited by cell age) or do you mean regenerating parts of our body (i.e. regenerating a lost finger)? Scientists don’t really know why we can’t fully regenerate a lost limb. Children can sometimes grow back lost fingertip, and adult can regenerate portions of damaged liver. After we’re born, our stem cells turn from pluripotent stem cells (able to become any cell types) to adult stem cells (can maintain the repair and cellular regeneration of their local environment). http://news.discovery.com/human/evolution/why-cant-humans-regenerate-body-parts-130823.htm

    • Photo: Matthew Moore

      Matthew Moore answered on 9 Mar 2015:

      Cool question and as Barbara said a massive (and to some, important) topic!

      One of the factors is telomere degradation. DNA in the form of chromosomes (when it’s all packed in) have a telomere at the bottom (it’s like that bit at the bottom of a zip which stops it pulling apart if you like).

      Telomeres degrade but some cells have an enzyme called telomerase which extends the telomere. This could be important in understanding ageing and certainly the stability of genes and cancer!

      Some people do live lots longer than others so there are lots of studies to find out if these people are of a particular genetic type, the problem is if they have similar lifestyles it’s difficult to determine if it is their lifestyles causing them to live longer, their genes or something else altogether!

Comments