Does Arsenic Contamination Affect DNA Methylation Patterns in a Wild Bird Population? An Experimental Approach

Pollutants, such
as toxic metals, negatively influence organismal
health and performance, even leading to population collapses. Studies
in model organisms have shown that epigenetic marks, such as DNA methylation,
can be modulated by various environmental factors, including pollutants,
influencing gene expression, and various organismal traits. Yet experimental
data on the effects of pollution on DNA methylation from wild animal
populations are largely lacking. We here experimentally investigated
for the first time the effects of early-life exposure to environmentally
relevant levels of a key pollutant, arsenic (As), on genome-wide DNA
methylation in a wild bird population. We experimentally exposed nestlings
of great tits (Parus major) to arsenic
during their postnatal developmental period (3 to 14 days post-hatching)
and compared their erythrocyte DNA methylation levels to those of
respective controls. In contrast to predictions, we found no overall
hypomethylation in the arsenic group. We found evidence for loci to
be differentially methylated between the treatment groups, but for
five CpG sites only. Three of the sites were located in gene bodies
of zinc finger and BTB domain containing 47 (ZBTB47), HIVEP zinc finger 3 (HIVEP3), and insulin-like
growth factor 2 mRNA binding protein 1 (IGF2BP1). Further studies are needed to evaluate whether epigenetic
dysregulation is a commonly observed phenomenon in polluted populations
and what are the consequences for organism functioning and for population
dynamics.