Conserved DNA methylation signatures in the prefrontal cortex of female newborn and juvenile guinea pigs following antenatal betamethasone exposure.

Antenatal corticosteroids (ACS) improve perinatal survival when there is a risk of preterm birth. Although evidence suggests an increased risk of developing neurobehavioural disorders in exposed offspring, the mechanisms involved remain largely unknown. Here, we investigated the DNA methylation patterns in the prefrontal cortex (PFC) of ACS-exposed guinea pig offspring. We hypothesized that differential methylation will be evident at both newborn and juvenile ages. In two separate cohorts, pregnant guinea pigs were administered a subcutaneous injection of saline or betamethasone (1 mg/kg) on gestational days 50/51 to mimic a single course of ACS. The gDNA was isolated from the PFC of term-born female offspring on postnatal day 1 (PND1, n = 7/group) and PND14 (n = 6-7/group) to identify differentially methylated CpG sites (DMCs) using reduced representative bisulphite sequencing. In the PND1 PFC, 1521 DMCs, annotating 144 genes were identified following ACS. Identified genes are involved in pathways regulating 'developmental cellular process'. In the PND14 PFC, 776 DMCs representing 46 genes were identified and enriched in 'synaptic signalling' pathways. Though no individual DMCs were identified at both PND1 and PND14, differential methylation was consistently observed at the binding sites of transcription factors PLAGL1, TFAP2C, ZNF263 and SP1 at both ages. We have established that ACS exposure leads to altered DNA methylation in the PFC of guinea pig offspring at both newborn and juvenile ages. Notably, a unique methylation signature was consistently observed at four key transcription factor binding sites at both post-natal time points. These changes may predispose the development of altered neurobehavioural phenotypes that have been described in ACS-exposed offspring.