Age estimation of captive Asian elephants (Elephas maximus) based on DNA methylation: An exploratory analysis using methylation-sensitive high-resolution melting (MS-HRM)

Age is an important parameter for bettering the understanding of
biodemographic trends-development, survival, reproduction and
environmental effects-critical for conservation. However, current age
estimation methods are challenging to apply to many species, and no
standardised technique has been adopted yet. This study examined the
potential use of methylation-sensitive high-resolution melting (MS-HRM), a
labour, time, and cost-effective method to estimate chronological age from
DNA methylation in Asian elephants (Elephas maximus). The objective of
this study was to investigate the accuracy and validation of MS-HRM use
for age determination in long-lived species, such as Asian elephants. The
average lifespan of Asian elephants is between 50-70 years but some have
been known to survive for more than 80 years. DNA was extracted from 53
blood samples of captive Asian elephants across 11 zoos in Japan, with
known ages ranging from a few months to 65 years. Methylation rates of two
candidate age-related epigenetic genes, RALYL and TET2, were significantly
correlated with chronological age. Finally, we established a linear,
unisex age estimation model with a mean absolute error (MAE) of 7.36
years. This exploratory study suggests an avenue to further explore MS-HRM
as an alternative method to estimate the chronological age of Asian
elephants.