Toward Understanding the Molecular Basis of Prenatal Stress as a Risk Factor for Autism Spectrum Disorder

It has long been posited that symptoms of autism spectrum disorder (ASD) may be the product of an imbalance of excitation and inhibition (E/I) in the brain. However, the E/I profile of neural substrates for ASD-relevant behavioral endophenotypes remains largely undefined on the molecular level with respect to the etiological risk factor of prenatal stress on the C57BL/6J genetic background, commonly used for the generation of preclinical models for the study of ASD. Pregnant C57BL/6J dams underwent three 45-minute restraint stress sessions per day from gestational day 9 to parturition. Offspring of the stressed dams (PRS mice) and non-stressed (NS) control mice underwent ASD-relevant behavioral testing in adulthood. Differential expression of genes related to excitatory and inhibitory neurotransmission was evaluated in the medial prefrontal cortex, amygdala, hippocampus, nucleus accumbens and dorsal striatum via qRT-PCR. PRS mice demonstrated reduced sociability and reciprocal social interaction along with increased marble burying behavior relative to NS controls. The PRS mouse behavioral phenotype was found to coincide with aberrant expression of glutamate and GABA marker genes (e.g. Grin1, Grin2b, Gls, Gat1, Reln) in neural substrates of social behavior. Ingenuity Pathway Analysis of NS and PRS mouse frontal cortex RNA sequencing data implicates dopamine D1 receptor – phosphoCREB-mediated transcriptional activation as one possible mechanism underlying the dysregulation of E/I balance in PRS mice. Such a mechanism may have been invoked as an attempt to attenuate the heightened and sustained proinflammatory response detected in the PRS brain by qRT-PCR in the present experiments. The successful pharmacological rescue of the PRS sociability deficit, and aberrant gene expression, using drugs with known epigenetic properties (e.g. clozapine (5 mg/kg) + 18-hr washout) indicates possible epigenetic regulation of genes that govern sociability. Identification of etiology-specific mechanisms underlying clinically relevant behavioral phenotypes may ultimately enhance the development of pharmacotherapies for the ASD population.