2023-07-06 06:00:05
Many species show differences in lifespan between males and females. A popular model to explain this observation is that the sex chromosomes contribute to aging through a “toxic” effect of the Y. This widely held hypothesis suggests that the presence of the chromosome And hit the longevity men. Image illustration Pixabay
For example, in lions, Asian elephants or killer whales, XX females live longer than their XY male counterparts. In the human species, XX individuals live in mean 7% longer than XY individuals. Compared to a population control, individuals with an XXY karyotype (Klinefelter syndrome) have a 2-year reduction in longevity, and those with an XYY karyotype have an even greater reduction. These data therefore suggest a negative effect of Y on longevity in humans.
Interestingly, some classes of animals show an opposite effect. In some birds and reptiles, the males have ZZ chromosomes while the females are ZW, the W being equivalent to the Y chromosome. In these species, the ZZ males outlive the females, their longevity can be much longer. This observation also extends to another living kingdom: dioecious plants with sex chromosomes, in which XY individuals have a duration of vie scaled down. These correlative studies suggest that the Y chromosome may be responsible for the differences in longevity between the sexes. However, this hypothesis has never been tested experimentally.
In Drosophila melanogaster, as in the other species mentioned above, XX female individuals live 10% longer than XY males. To directly query this theory of the “toxic Y” scientists have generated tissues and lines of drosophila in which they directly manipulated the size and name of Y chromosomes using an innovative method using CRISPR-Cas9.
Y chromosomes of different sizes have been produced using CRISPR-Cas9 in Drosophila. The presence or size of the Y chromosome does not lead to a decrease in longevity in males, nor does it affect sex dimorphisms in size and incidence of development of intestinal cancers.
© Julien Marcetteau and Bruno Hudry
Using this genetic approach, they found that altering the number or size of the Y chromosome had no impact on male longevity. This discovery refutes the hypothesis that the Y chromosome has a toxic effect and shortens the lifespan of males. Using the same genetic manipulations, the scientists show that the Y chromosome is not more important for other key physiological sex differences, such as sex differences in adult somatic stem cell behavior and cancers. intestinal.
The implications of these findings are far-reaching because sex differences in longevity are observed in most animals, including humans. Overall, these results reject the “toxic Y” hypothesis which posits that the Y chromosome leads to reduced lifespan in XY individuals.
Reference
Y chromosome toxicity does not contribute to sex-specific differences in longevity.
Delanoue R, Clot C, Leray C, Pihl T, Hudry B.
Nat Ecol Evol. 2023 Jun 12. DOI: 10.1038/s41559-023-02089-7. PMID: 37308701.
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