The Y chromosome does not shorten the lifespan of males

Many species show differences in lifespan between males and females. A popular way of explaining this observation is that sex chromosomes contribute to aging through a "toxic" effect of the Y. This widely held hypothesis suggests that the presence of the Y chromosome impacts male longevity. In lions, Asian elephants and killer whales, for example, XX females live longer than their XY male counterparts. In humans, XX individuals live on average 7% longer than XY individuals. Compared to a control population, individuals with an XXY karyotype (Klinefelter syndrome) have a two-year shorter lifespan, and those with an XYY karyotype have an even shorter one. These data also suggest a negative effect of Y on longevity in humans. Interestingly, some animal classes show the opposite effect.

In some birds and reptiles, males have ZZ chromosomes while females are ZW, the W being equivalent to the Y chromosome. In these species, ZZ males outlive females, and can live much longer. This observation extends to another living species. In dioecious plants with sex chromosomes, XY individuals have a shorter lifespan. These correlative studies suggest that the Y chromosome may be responsible for differences in longevity between the sexes. However, this hypothesis has never been tested experimentally.

To directly examine this "toxic Y" theory, Rénald Delanoue and Charlène Clot, from the Sex and Cell Physiology team at the Valrose Institute of Biology, generated Drosophila tissues and lines in which they directly manipulated the size and number of Y chromosomes using an innovative CRISPR-Cas9 method.

Using this genetic approach, they discovered that a modificaton in 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. They used the same genetic manipulations to show that the Y chromosome does not have an impact either on other key physiological differences between the sexes. For example, they studied the impact of the Y chromosome on sex differences in adult somatic stem cell behavior and intestinal cancers. The implications of these findings are considerable, as differences in longevity between
the sexes are observed in most animals, including humans. Overall, these results reject the "toxic Y" hypothesis, which postulates that the Y chromosome leads to a shorter lifespan in XY individuals.

For more information

Y chromosome toxicity does not contribute to sex-specific differences in longevity
Rénald Delanoue, Charlène Clot, Chloé Leray, Thomas Pihl & Bruno Hudry
Nature Ecology and Evolution 2023

Illustration

Y chromosomes of different sizes produced using CRISPR-Cas9 in Drosophila. The presence or size of the Y chromosome does not reduce longevity in males, nor does it affect sexual dimorphisms in size and incidence of intestinal cancer development.
 

Contact

Bruno Hudry - CNRS Research Fellow - +33 4 89 15 07 60 - Bruno.Hudry@univ-cotedazur.fr