Molecular aging of North Atlantic right whales (Eubalaena glacialis)

Abstract

Knowing the age of individuals within a population provides a wealth of information that is important for understanding aspects of their biology, including many aspects that are important for conservation. Some of these include the relative rates of birth, survival, immigration, and emigration for each age class. This gives useful information for estimating trends over time and estimating extinction probabilities. Cetaceans (whales, dolphins, and porpoises) are challenging to study because they spend the vast majority of their lives below the surface of the water and their habitats are widespread across oceans. Current methods for estimating age in baleen whales are limited. Recent studies have found that methylation patterns associated with certain genes change consistently over time, and therefore provide a "molecular clock" that can be used to estimate the age of individuals. This study investigated whether the age related methylation patterns exist at CpG sites in the GRIA2, KLF14, and TET2 genes in North Atlantic right whales (Eubalaena glacialis). Specifically, methylation patterns were examined for 40 known-age individuals, representing males and females from throughout the spectrum of known ages, to understand the relationship between CpG methylation and age at these age-related CpG sites. The results showed that the levels of methylation at these sites correspond with the age of the individuals, but that methylation patterns were also influenced by how long the tissue samples were in storage. Therefore, this approach can be used to molecularly estimate age in North Atlantic right whales, but the age of the samples must also be taken into account. Future studies should investigate how methylation patterns degrade and what storage solutions are best to prevent degradation.