DNA methylation predicts immune gene expression in introduced house sparrows Passer domesticus

Abstract

Populations undergoing range expansions are often faced with novel selective pressures, and to cope with such challenges, populations must either adapt quickly or exhibit phenotypic plasticity. This latter option allows for rapid phenotypic adjustments and persistence in novel environments, and thus could be advantageous at range‐edges. Our previous research on house sparrows in Kenya – a site of ongoing range expansion – and a growing literature suggests that invasion success is facilitated by epigenetic regulation of gene expression. Previously, we found 1) differences in the expression of a microbial surveillance gene (i.e. Toll‐like receptor 4‐TLR4), and 2) extensive variation in genome‐wide DNA methylation among house sparrows across Kenya. Here, our goal was to investigate whether these two observations are related, specifically whether DNA methylation within a target sequence upstream of the TLR4 transcription start site is associated with variation in TLR4 expression. We found that DNA methylation in the aforementioned region was quite variable among individuals, and variation at one CpG site predicted differences in TLR4 expression. Moreover, we found genetic variation within the same sequence upstream of the TLR4 exon, but this variation did not predict TLR4 expression. To our knowledge, this is the first study to demonstrate an association between DNA methylation and the expression of an ecologically relevant trait in a range‐expanding vertebrate.

Urbanization is associated with modifications in DNA methylation in a small passerine bird

“…While methylation at CpG‐rich promoters is often associated with stable repression of gene expression, that is gene silencing, DNA methylation within the gene body has been shown to be positively correlated with gene expression in mammalian tissues (Jones, 2012; Lev Maor et al., 2015). Increasingly, DNA methylation patterns are being shown to be responsive to environmental cues, in wild (Kilvitis et al., 2019; Laubach et al., 2019; Lea et al., 2016) and captive (Jimeno et al., 2019; Viitaniemi et al., 2019) animal populations, suggesting a critical role for DNA methylation as a rapid regulator of phenotypic divergence and adaptation.…”

Screening H3 Histone Acetylation in a Wild Bird, the House Sparrow (Passer Domesticus)

“…We also found a relationship between H3 acetylation and TLR-4 expression. TLR-4 is a receptor that detects Gram-negative bacteria and ultimately leads to an inflammatory response ( Kilvitis et al. 2019 ).…”

“…Indeed, the house sparrow ( Passer domesticus ) has been successfully introduced throughout the world ( Liebl et al. 2015 ), and DNA methylation is important at the individual level to variation in gene expression ( Kilvitis et al. 2019 ) and at the population level in terms of success in colonizing new areas ( Liebl et al.…”

Diverging Epigenetic Responses to Wildfire History in Two Sympatric Lizards

“…Such changes in DNA methylation have been linked to phenotypic changes such as morphological variation (Cubas et al, 1999) and physiological changes such as cellular signaling (Baerwald et al, 2016; Kubota, 2016) and regulation of ion pumps (Artemov et al, 2017). Changes in DNA methylation can also respond to immune challenge arising via infection by pathogens, parasites, or both (Hu et al, 2018; Kilvitis et al, 2019). Finally, DNA methylation appears to affect life history components.…”