Offspring Global DNA Methylation is not Affected by Parental Developmental Stress Experience in a Passerine Species

Rapid phenotypic change may be mediated by intergenerational transmission of early developmental experiences. In birds, exposure to glucocorticoids during early development can alter global DNA methylation and gene expression. However, DNA methylation is labile, and it is currently unclear whether the impacts of stress suffered during juvenile development are transmitted intergenerationally through this mechanism. We tested this, for the first time in birds, by quantifying the impact of parental developmental stress on offspring global DNA methylation. We exposed nestling zebra finches (Taeniopygia castanotis) to glucocorticoid or control treatments prior to fledging. As adults, birds from both treatments were housed communally and allowed to breed. We sampled their embryos at 5 days post lay and assessed global DNA methylation using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS). We found no evidence that parental developmental experience impacted offspring embryonic global DNA methylation ratios. Global DNA methylation ratios did not differ between the offspring of pairs matched or mismatched for parental developmental treatment, nor between offspring grouped by parental maternal-paternal developmental treatment group pair combinations. We found a positive relationship between egg volume and embryonic global DNA methylation ratios. Whilst our results fail to detect any intergenerational impact of developmental stress on global methylation levels, we suggest that a lack of temporal or spatial resolution across the genome may have masked relevant effects. Further avian research should investigate the intergenerational impacts of early developmental stress at the base-pair level to determine the epigenetic consequences of glucocorticoid exposures.