Abstract 128 – Age estimation based on blood DNA methylation: A simple method applicable to multiple bear species

Michito Shimozuru, Shiori Nakamura, Jumpei Yamazaki, Yojiro Yanagawa,
Nobutaka Sato, Yusuke Honda, Hideyuki Ito, Toshio Tsubota

Age is an essential information for understanding the ecology and management of bears. Age
estimation has been conducted by counting cementum annuli of the teeth, however, this
method is highly invasive as it requires tooth extraction. Recently, we have established age
estimation method based on blood DNA methylation levels in brown bears. The purpose of this
study was to clarify whether this method is applicable to other bear species. We collected blood
and extracted DNA from captive bears of known ages, including polar bears (17 bears, 20
samples), sun bears (8 bears, 10 samples), and Asian black bears (16 bears; 14 Japanese black
bears and 2 Himalayan black bears). We performed bisulfite pyrosequencing to obtain DNA
methylation levels at 4 cytosine-phosphate-guanine (CpG) sites adjacent to a single gene,
SLC12A5. High positive correlation between age and methylation levels of all 4 CpGs was found
in all three bear species. The application of brown bear age estimation model revealed that
mean absolute errors (i.e., the mean absolute values of the difference between the estimated
age and the actual age) was 2.22, 2.19, and 1.40 years, for polar bears, sun bears, and Asian
black bears, respectively. These values were comparable to those in brown bears (average
absolute error was 1.30 years), suggesting that the age estimation model established for brown
bears is commonly applicable to different bear species. The current study will contribute to
ecological research, conservation, and management of bear species.