I pass on this nugget by Beverly Purnell in the Editor's Choice section of this week's Science Magazine noting an interesting paper by Sugrue et al. First her summary, then the abstract of the Sugrue et al. paper.
As we age, our genetic material changes, not only through DNA mutation but also by epigenetic modification. Indeed, chronological age can be estimated based on analysis of DNA methylation. Male and female mammals display different average life spans, and a role for sex hormones is expected in this effect. Sugrue et al. established an epigenetic clock in sheep by examining methylated DNA in samples from blood and ears. They show that castration extends an animal's life span and feminizes the epigenome at specific androgen-regulated loci during aging.The Abstract:
In mammals, females generally live longer than males. Nevertheless, the mechanisms underpinning sex-dependent longevity are currently unclear. Epigenetic clocks are powerful biological biomarkers capable of precisely estimating chronological age and identifying novel factors influencing the aging rate using only DNA methylation data. In this study, we developed the first epigenetic clock for domesticated sheep (Ovis aries), which can predict chronological age with a median absolute error of 5.1 months. We have discovered that castrated male sheep have a decelerated aging rate compared to intact males, mediated at least in part by the removal of androgens. Furthermore, we identified several androgen-sensitive CpG dinucleotides that become progressively hypomethylated with age in intact males, but remain stable in castrated males and females. Comparable sex-specific methylation differences in MKLN1 also exist in bat skin and a range of mouse tissues that have high androgen receptor expression, indicating that it may drive androgen-dependent hypomethylation in divergent mammalian species. In characterizing these sites, we identify biologically plausible mechanisms explaining how androgens drive male-accelerated aging.