Epigenetic mediation of the onset of reproduction in a songbird

Abstract

11Climate change significantly impacts natural populations, particularly phenology traits, like the seasonal 12 onset of reproduction in birds. This impact is mainly via plastic responses in phenology traits to changes in the 13 environment, but the molecular mechanism mediating this plasticity remains elusive. Epigenetic modifications can 14 mediate plasticity and consequently constitute promising candidates for mediating phenology traits. Here, we used 15 genome-wide DNA methylation profiles of individual great tit (Parus major) females that we blood sampled 16 repeatedly throughout the breeding season. We demonstrate rapid and directional variation in DNA methylation 17 within the regulatory region of genes known to play key roles in avian reproduction that are in line with observed 18 changes in gene expression in chickens. Our findings provide an important step towards unraveling the molecular 19 mechanism mediating a key life history trait, an essential knowledge-gap for understanding how natural 20 populations may cope with future climate change. 21 22 seasonal onset of egg laying. As a first step, we investigated whether great tit females show within-individual and 32 short-term variation in DNA methylation that corresponds to changes in the reproductive state of females. We 33 therefore housed breeding pairs in climate-controlled aviaries to blood sample each female repeatedly throughout 34 the breeding season and used these repeated samples for methylation profiling. 35We found rapid and directional variation in DNA methylation at the time females prepared to initiate egg 36 laying that is located within the regulatory region of genes that have previously described functions for avian 37 reproduction. Although future work is needed to establish a causal link between the observed temporal variation 38 in DNA methylation and the onset of reproduction in female great tits, our work highlights the potential role for 39 epigenetic modifications in mediating an essential phenology trait that is sensitive to temperatures. 40 41

From maternal glucocorticoid and thyroid hormones to epigenetic regulation of gene expression: an experimental study in a wild bird species

“…mechanisms translating the information of a genotype to various phenotypes; Waddington 1942) of the hormonal pathways could be one such mechanism (Jimeno et al 2019;Ruiz-Raya et al 2023). One of the best-studied epigenetic mechanisms is DNA methylation, which facilitates changes in gene expression, imprinting, and transposon silencing (Jaenisch & Bird 2003, Vogt 2021, Laine et al 2022, and is known to be affected by age, environmental quality, and physiological condition (De Paoli-Iseppi et al 2018;Lindner et al 2021;Mäkinen et al 2022). Epigenetic alterations may function as a tool for individuals to acclimatize to changing environmental conditions, but they may also mediate transgenerational adaptation (Guerrero-Bosagna et al 2018;Sepers et al 2021;Vogt 2021).…”