Oral Presentation Australian Epigenetics Alliance Conference 2022

Male-specific DNA aging and building the androgen clock (#15)

Victoria J Sugrue 1 , Joseph A Zoller 2 , Pritika Narayan 3 , Ake T Lu 4 , Oscar J Ortega-Recalde 1 , Matthew J Grant 3 , C. Simon Bawden 5 , Skye R Rudiger 5 , Amin Haghani 4 , Donna M Bond 1 , Reuben R Hore 6 , Karen E Sears 7 , Nan Wang 8 , X. William Yang 8 9 , Russell G Snell 3 , Rebecca Campbell 1 , Mike Garratt 1 , Steve Horvath 4 , Timothy A Hore 1
  1. Department of Anatomy, University of Otago, Dunedin, Otago, New Zealand
  2. Department of Biostatistics, Fielding School of Public Health, UCLA, Los Angeles, California, USA
  3. Applied Translational Genetics Group, School of Biological Sciences, Centre for Brain Research, The University of Auckland, Auckland, New Zealand
  4. Department of Human Genetics, David Geffen School of Medicine, UCLA, Los Angeles, California, USA
  5. Livestock and Farming Systems, South Australian Research and Development Institute, Roseworthy, South Australia, Australia
  6. Blackstone Hill Station, Becks, Omakau, New Zealand
  7. Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, California, USA
  8. Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles, California, USA
  9. Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, UCLA, Los Angeles, California, USA

In mammals, females generally live longer than males, significantly so for sheep (1). Nevertheless, the mechanisms underpinning sex-dependent longevity are currently unclear. Epigenetic clocks are powerful biomarkers capable of precisely estimating chronological age and identifying novel factors influencing the aging rate using only DNA methylation data (2). We developed the first epigenetic clock for domesticated sheep (Ovis aries) using DNA from 425 New Zealand and Australian Merino sheep (3). This clock is capable of predicting chronological age with a median absolute error of 5.1 months using DNA methylation data at 185 CpG sites throughout the genome. 

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 it may drive androgen-dependent hypomethylation in divergent mammalian species. In characterising these sites, we identify biologically plausible mechanisms explaining how androgens drive male-accelerated aging in sheep and other mammals. 

Using a single androgen-sensitive CpG site in MKLN1, we have developed the Androgen Clock – a rapid and effective tool to measure the period of androgen exposure. In male sheep, this clock is able to accurately distinguish intact males from castrates, and has a median absolute error of 4.1 months. The Androgen Clock provides a rare opportunity to warp the ‘ticking rate’ of an epigenetic time predictor in a way that does not affect cellular viability, and could aid in diagnosis of conditions characterised by long-term elevated androgens, such as polycystic ovary syndrome (PCOS).

  1. Lemaître, J.-F. et al. Sex differences in adult lifespan and aging rates of mortality across wild mammals. Proc. Natl. Acad. Sci. 117, 8546–8553 (2020).
  2. Horvath, S. DNA methylation age of human tissues and cell types. Genome Biol. 14, 3156 (2013).
  3. Sugrue, V. J. et al. Castration delays epigenetic aging and feminizes DNA methylation at androgen-regulated loci. Elife 10, e64932 (2021).