Introduction.This database includes the raw data linked with the paper “Sex-dependent association between variability in infants' OXTR methylation at birth and negative affectivity at 3 months”. This publication is part of the longitudinal and multi-centric “Measuring the outcomes of maternal COVID-19-related prenatal exposure (MOM-COPE)” research project. In this paper, we report data on sex differences in the association between the infants’ DNA methylation of the oxytocin receptor gene (OXTRm) at birth and negative affectivity at 3 months of age. Procedures. Infants’ methylation status was assessed in 13 CpG sites within the OXTR gene intron 1 region (chr3: 8810654–8810919) in buccal cells at birth while 3-months-age infants’ negative affectivity was assessed by mothers using the Infant Behavior Questionnaire- Revised short-form (Gartstein & Rothbart, 2003). Analytical plan. A principal component analysis (PCA) was used to reduce the number of CpG sites into a smaller set of factors (i.e., PC1 and PC2). Sex differences in mean levels of methylation at all CpG sites as well as at PC1 and PC2 were tested through independent sample t-tests. Separate hierarchical regression models were performed to evaluate the independent and interactive effects of infant OXTRm (respectively, PC1 and PC2) and sex on negative affectivity. Findings in brief. OXTRm at 12 CpG sites was higher in females than in males. Moreover, higher infants’ OXTRm at 6 spe- cific CpG sites was associated with greater negative affectivity in males, but not in females. These findings advance the possibility that epigenetic pathways involving OXTRm may be one such factor which operates through sex-dependent mechanisms to shape variability in temperamental negative affectivity.

Funding: 5 x 1000 (2017); Fondazione Roche "Per la Ricerca Indipendente" 2020 (Italy)