Why do we need telomeres?

Over the past 30 years we have learned a lot about telomeres, including what they are and where they are found. In this blog we will discuss why exactly we need telomeres and the important processes that they have a role in.

What are telomeres made of?

Telomeres are repetitive DNA sequences found at the end of linear chromosomes. In mammals these are made up of tandem repeats of the nucleotide sequence TTAGGG and are bound to the protein complex shelterin. Some human cells contain as many as 1,500 to 2,000 repeats of this sequence at the ends of each chromosome.

Why do we need telomeres?

1. Telomeres protect our genetic material

Telomeres act as protective caps on the ends of our chromosomes and prevent damage and fusion with other chromosomes. A useful analogy for this can be the way an aglet of a shoelace prevents fraying, unravelling and tangling of laces.

In addition, during the copying of genetic material, as part of cell division, the very ends of chromosomes cannot be replicated. We can think of the telomeres acting as buffers, ensuring that it is the telomeric repetitive sequence that is not replicated, rather than important coding genes required for healthy cell functioning.

2. Telomeres are involved in biological aging

With each cell division, telomeric repeats are lost, shortening the telomeres on each chromosome. When the telomeres become critically short the cell will stop dividing, this is known as cellular senescence. Therefore, telomere length is a known part of the process for regulating cell life and biological aging.

3. Telomeres can be implicated in certain diseases

As the number of repeats determines the maximum replicative life span of a cell, being able to measure telomere length can be very important in the diagnosis of telomere biology disorders (TBDs) and other conditions where the replicative potential of stem cells is impaired. Find out more about TBDs in this dedicated blog.

Telomere length is also of particular interest when considering malignant tumorigenesis i.e. cancer. In many different types of cancer extremely short telomeres can cause damage to the chromosomes (genetic instability) which can then prompt an increased amount of telomerase activity in the cells, often through the acquisition of other abnormalities affecting its regulation.

Telomerase is the enzyme responsible for replenishing the telomeric DNA sequence, thus elongating cell life and enabling further cell division and tumor growth.

Telomere length can be accurately and reliably measured using the Flow FISH protocol that is conducted at RepeatDx. From one blood sample we can provide telomere length measurements for up to six cell types.

Learn more about the telomere length testing we offer and how to order a telomere test here.

Sources

Jafri, M, A. et al. Roles of telomeres and telomerase in cancer, and advances in telomerase-targeted therapies. Genome medicine vol. 8,1 69. 20 Jun. 2016. https://doi.org/10.1186/s13073-016-0324-x.

R K Moyzis, R, K. et al.  A highly conserved repetitive DNA sequence, (TTAGGG)n, present at the telomeres of human chromosomes. Proceedings of the National Academy of Sciences. Sep 1988, 85 (18) 6622-6626. https://doi.org/10.1073/pnas.85.18.6622.