Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
Behavioural Ecology Group, Wageningen University & Research (WUR), Wageningen, The Netherlands.
Mol Ecol. 2023 Jul;32(14):3960-3974. doi: 10.1111/mec.16973. Epub 2023 May 8.
The environment experienced during early life is a crucial factor in the life of many organisms. This early life environment has been shown to have profound effects on morphology, physiology and fitness. However, the molecular mechanisms that mediate these effects are largely unknown, even though they are essential for our understanding of the processes that induce phenotypic variation in natural populations. DNA methylation is an epigenetic mechanism that has been suggested to explain such environmentally induced phenotypic changes early in life. To investigate whether DNA methylation changes are associated with experimentally induced early developmental effects, we cross-fostered great tit (Parus major) nestlings and manipulated their brood sizes in a natural study population. We assessed experimental brood size effects on pre-fledging biometry and behaviour. We linked this to genome-wide DNA methylation levels of CpG sites in erythrocyte DNA, using 122 individuals and an improved epiGBS2 laboratory protocol. Brood enlargement caused developmental stress and negatively affected nestling condition, predominantly during the second half of the breeding season, when conditions are harsher. Brood enlargement, however, affected nestling DNA methylation in only one CpG site and only if the hatch date was taken into account. In conclusion, this study shows that nutritional stress in enlarged broods does not associate with direct effects on genome-wide DNA methylation. Future studies should assess whether genome-wide DNA methylation variation may arise later in life as a consequence of phenotypic changes during early development.
早期生活经历是许多生物生命中的一个关键因素。这种早期生活环境对形态、生理和适应性都有深远的影响。然而，介导这些影响的分子机制在很大程度上是未知的，尽管它们对于我们理解在自然种群中诱导表型变异的过程是必不可少的。DNA 甲基化是一种表观遗传机制，它被认为可以解释生命早期环境诱导的表型变化。为了研究 DNA 甲基化变化是否与实验诱导的早期发育效应有关，我们对大山雀（Parus major）的巢雏进行了交叉抚育，并在一个自然研究种群中操纵了它们的巢雏数量。我们评估了实验巢雏数量对离巢前生物测量和行为的影响。我们将这与红细胞 DNA 中 CpG 位点的全基因组 DNA 甲基化水平联系起来，使用了 122 个个体和改进的 epiGBS2 实验室方案。巢雏数量的增加导致了发育压力，并对巢雏的状况产生了负面影响，主要是在繁殖季节的后半段，那时条件更加恶劣。然而，巢雏数量的增加仅在一个 CpG 位点与巢雏的 DNA 甲基化有关，而且只有在考虑到孵化日期的情况下才会有关联。总之，这项研究表明，在扩大的巢雏中营养压力不会与全基因组 DNA 甲基化的直接影响相关联。未来的研究应该评估全基因组 DNA 甲基化变异是否可能在生命后期作为早期发育过程中表型变化的结果而出现。
