Telomeres are inherited

Late-conceived grandfathers gave their Filipino grandchildren long telomeres

Polina Loseva, "The Attic"

The older a man is, the longer the telomeres in his spermatozoa. Therefore, the children of older fathers inherit elongated telomeres and, perhaps, a chance to live longer than their peers, whose fathers had children in their youth. A group of American scientists suggested that this effect can be transmitted to subsequent generations. Researchers measured telomere length in more than 3,000 Filipinos and found that this trait is inherited in at least two generations, both on the paternal and maternal lines. Although the strength of the effect decreases in each subsequent generation, the authors of the work believe that it can serve to adapt the offspring to the living conditions of the parents.

Telomeres – the end sections of chromosomes – play the role of a kind of shock absorbers for DNA. With each cell division, the DNA strands shorten, and the telomeres take the hit. They, like a protective layer, are erased, protecting significant genetic information from extinction. When telomeres become too short, cell division stops, because then it will start losing genes. Shortening of telomeres is sometimes called one of the main causes of tissue wear: there are no dividing cells left in them that could replace the old and damaged ones. And the initial length of telomeres correlates with the lifespan of the organism and its health.

With age, telomeres shorten in most cells of human tissues. The exception is the male reproductive system: in the progenitor cells of spermatozoa, telomeres, on the contrary, grow over time. It is still unclear what exactly this may be related to. Perhaps telomerase, an enzyme that builds up the ends of chromosomes, works more actively in this tissue than in others. Or maybe cells with longer telomeres are more viable and survive their competitors from the tissue. Anyway, the older the father, the longer the telomeres on the chromosomes in his sperm, and half of these chromosomes he passes on to his children. This does not work with mothers: with age, telomeres in eggs, on the contrary, are slightly shortened. But when scientists measure the length of telomeres in human cells, they tend to focus on the average value, so telomeres are longer in late children.

American researchers decided to check whether the length of telomeres is transmitted to the next generations. After all, if a child inherited the long ends of chromosomes from his father, then they should be passed on to his children, regardless of how old he conceived them. Scientists used data from a longitudinal project that monitored the health and nutrition of Filipinos. It began its work back in 1983-1984, when several thousand pregnant women were selected for monitoring. From then until 2005, their children and themselves were regularly examined. In 2016, researchers measured the telomere length of people born in 1983-1984, their parents, as well as grandparents and great-grandparents. In total, the sample included more than 3,000 Filipinos.

It turned out that the effect of "older father – longer telomeres" is reproduced in generations of children and grandchildren, and in the second generation it is weaker than in the first. Scientists estimated the standard deviation of the offspring's telomere length in terms of the father's age at conception (i.e., they determined how much the influence of the father's age on the child's telomeres was not accidental), and it fell twice from fathers to children, and three times from children to grandchildren. It was not possible to detect the effect in great- and great-grandchildren, but the authors of the work attribute this to the insufficient sample size of older generations.

Interestingly, the length of telomeres was transmitted both on the paternal and maternal lines, that is, the shortening of telomeres characteristic of eggs did not manifest itself as strongly as the elongation of telomeres in spermatozoa.

The authors of the paper (Eisenberg et al., Older paternal ages and grandpaternal ages at conception predict longer telomeres in human descendants) believe that inheritance of long telomeres may be not just a consequence of paternal age at conception, but a specially acquired adaptive mechanism. Maintaining telomere length requires energy expenditure. And if an organism exists in unfavorable conditions, then it is more profitable for it to spend resources on reproduction than on lengthening the ends of DNA, and at the same time – on prolonging life in general.

The father, who conceived a child in old age, was presumably in favorable conditions, since he was able to live up to this age. This means that his son, who inherited long telomeres, can afford to spend more energy on maintaining them and postpone reproduction for later, since his paternal age is evidence that there is no direct threat to life in this environment.

At the same time, if a father has children at a young age, this may be due to conditions that are not the most favorable for a long and carefree life, and then his son will also have to procreate as early as possible and not waste energy on lengthening telomeres. In the following works, apparently, the authors will have to check whether the physiological characteristics of the father (for example, smoking or lifestyle) affect the length of telomeres, and whether the principle of inheritance changes under their influence.

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