Screening H3 histone acetylation in a wild bird, the house sparrow
(Passer domesticus)
Abstract
Epigenetic mechanisms are increasingly understood to have major impacts
across ecology. However, one molecular epigenetic mechanism, DNA
methylation, currently dominates the literature. A second mechanism,
histone modification, is likely important to ecologically relevant
phenotypes and thus warrants investigation, especially because molecular
interplay between methylation and histone acetylation can strongly
affect gene expression. There are a limited number of histone
acetylation studies on non-model organisms, yet those that exist show
that it can impact gene expression and phenotypic plasticity. Wild birds
provide an excellent system to investigate histone acetylation, as
free-living individuals must rapidly adjust to environmental change.
Here, we screen histone acetylation in the house sparrow (Passer
domesticus); we studied this species because DNA methylation was
important in the spread of this bird globally. This species has one of
the broadest geographic distributions in the world, and part of this
success is related to the way that it uses methylation to regulate its
gene expression. Here, we verify that a commercially available assay
that was developed for mammals can be used in house sparrows. We
detected high variance in histone acetylation among individuals in both
liver and spleen tissue. Further, house sparrows with higher epigenetic
potential in the Toll Like Receptor-4 (TLR-4) promoter (i.e., CpG
content) had higher histone acetylation in liver. Also, there was a
negative correlation between histone acetylation in spleen and TLR-4
expression. In addition to validating a method for measuring histone
acetylation in wild songbirds, this study also shows that histone
acetylation varies in an ecologically relevant way, adding a new study
option for ecological epigenetics.