Associations of peripheral blood DNA methylation and estimated monocyte proportion differences during infancy with toddler attachment style

Attachment is a motivational system promoting felt security to a caregiver resulting in a persistent internal working model of interpersonal behavior. Attachment styles are developed in early social environments and predict future health and development outcomes with potential biological signatures, such as epigenetic modifications like DNA methylation (DNAm). Thus, we hypothesized infant DNAm would associate with toddler attachment styles. An epigenome-wide association study (EWAS) of blood DNAm from 3-month-old infants was regressed onto children's attachment style from the Strange Situation Procedure at 22-months at multiple DNAm Cytosine-phosphate-Guanine (CpG) sites. The 26 identified CpGs associated with proinflammatory immune phenotypes and cognitive development. In post-hoc analyses, only maternal cognitive-growth fostering, encouraging intellectual exploration, contributed. For disorganized children, DNAm-derived cell-type proportions estimated higher monocytes -cells in immune responses hypothesized to increase with early adversity. Collectively, these findings suggested the potential biological embedding of both adverse and advantageous social environments as early as 3-months-old.

Stable reprogramming of brain transcription profiles by the early social environment in a cooperatively breeding fish

Adult social behaviour can be persistently modified by early-life social experience. In rodents, such effects are induced by tactile maternal stimulation resulting in neuroendocrine modifications of the hypothalamic-pituitary-adrenal axis involved in stress responsiveness. Whether similar long-term alterations can occur in the hypothalamic-pituitary-interrenal (HPI) axis of poikilothermic vertebrates is unknown. We compared the expression of four genes of the HPI axis in adults of the cooperatively breeding cichlid Neolamprologus pulcher, which had been exposed to two early-life social treatments 1.5 years prior to brain sampling. Fish reared with parents and siblings had less brain expression of corticotropin-releasing factor and of the functional homologue of the mammalian glucocorticoid receptor (GR1) than individuals reared with same-age siblings only. Expression of the mineralocorticoid receptors (MR) did not differ between treatments, but the MR/GR1 expression ratio was markedly higher in fish reared with parents and siblings. Thus, we show here that early social experience can alter the programming of the stress axis in poikilothermic vertebrates, suggesting that this mechanism is deeply conserved within vertebrates. Moreover, we show for the first time that reprogramming of the stress axis of a vertebrate can be induced without tactile stimulation by parents.