Autism Spectrum Disorder (ASD) has been associated with a complex interplay between genetic and environmental factors. Prenatal stress exposure has been identified as a possible risk factor, although most stress-exposed pregnancies do not result in ASD. The serotonin transporter (SERT) gene has been linked to stress reactivity, and the presence of the SERT short (S)-allele has been shown to mediate the association between maternal stress exposure and ASD. In a mouse model, we investigated the effects of prenatal stress exposure and maternal SERT genotype on offspring behavior and explored its association with maternal microRNA (miRNA) expression during pregnancy. Pregnant female mice were divided into four groups based on genotype (wildtype or SERT heterozygous knockout (Sert-het)) and the presence or absence of chronic variable stress (CVS) during pregnancy. Offspring behavior was assessed at 60 days old (PD60) using the three-chamber test, open field test, elevated plus-maze test, and marble-burying test. We found that the social preference index (SPI) of SERT-het/stress offspring was significantly lower than that of wildtype control offspring, indicating a reduced preference for social interaction on social approach, specifically for males. SERT-het/stress offspring also showed significantly more frequent grooming behavior compared to wildtype controls, specifically for males, suggesting elevated repetitive behavior. We profiled miRNA expression in maternal blood samples collected at embryonic day 21 (E21) and identified three miRNAs (mmu-miR-7684-3p, mmu-miR-5622-3p, mmu-miR-6900-3p) that were differentially expressed in the SERT-het/stress group compared to all other groups. These findings suggest that maternal SERT genotype and prenatal stress exposure interact to influence offspring behavior, and that maternal miRNA expression late in pregnancy may serve as a potential marker of a particular subtype of ASD pathogenesis.

While genetic mechanisms in neurodevelopmental disorders are well studied, the mechanisms of environmental factors such as prenatal stress are less understood. Our lab previously characterized miRNA changes associated with stress during pregnancy in mouse brains and in maternal blood from mothers of children with ASD and indicated that prenatal stress can be linked to epigenetic markers. These miRNAs could be used as discovery biomarkers for stress exposure, as well as predictors of neurodevelopmental outcomes. In this pilot study, we gathered saliva samples and stress survey questionnaires from 83 pregnant African American women (ages 18–40) at the time of their ultrasound performed at 20 weeks. miRNA analysis was performed on the 10 highest- and 10 lowest-stress subjects. Out of 6631 miRNAs examined, 34 had significant differential expression, with 5 being upregulated and 29 downregulated in the high-stress group. Predicted targets of differentially expressed miRNAs revealed significant enrichment in neurodevelopmental pathways, including forebrain development, sensory system development, and neuronal growth regulation. This may suggest the potential developmental salience of these miRNA profiles. Future research will examine the neurodevelopmental outcomes of these pregnancies to determine the predictive potential of these miRNAs. This may help identify individuals at greatest risk after stress exposure during pregnancy.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by restricted social communication and repetitive behaviors. Prenatal stress is critical in neurodevelopment and increases risk for ASD, particularly in those with greater genetic susceptibility to stress. Docosahexaenoic acid (DHA) is one of the most abundant ω-3 fatty acids in the membrane phospholipids of the mammalian brain, and dietary DHA plays an important role in brain development and maintenance of brain structure. In this study, we investigated whether peri-natal supplementation of DHA can alleviate autistic-like behaviors in a genetic risk/stress mouse model and how it alters lipid peroxidation activity and GABAergic system gene expression in the forebrain. Pregnant heterozygous serotonin transporter knockout (SERT-KO) and wild-type (WT) dams were placed in either non-stressed control conditions or chronic variable stress (CVS) conditions and fed either a control diet or a DHA-rich (1% by weight) diet. Offspring of each group were assessed for anxiety and autism-associated behavior at post-natal day 60 using an open field test, elevated plus maze test, repetitive behavior, and the 3-chamber social approach test. A liquid chromatography-mass spectrometry (LC-MS)-based method was used to follow changes in levels of lipid peroxidation products in the cerebral cortex. Male offspring of prenatally stressed SERT-het KO dams exhibited decreased social preference behaviors and increased repetitive grooming behaviors compared to WT control offspring. Moreover, DHA supplementation in male SERT-het mice decreased frequency of grooming behaviors albeit showing no associated effects on social behaviors. Regardless of stress conditions, supplementation of DHA to the WT mice did not result in alterations in grooming nor social interaction in the offspring. Furthermore, no apparent changes were observed in the lipid peroxidation products comparing the stressed and non-stressed brains. Gad2 was downregulated in the cortex of female offspring of prenatally stressed SERT-KO dams, and this change appeared to be rescued by DHA supplementation in offspring. Gad2 was upregulated in the striatum of male offspring of prenatally stressed SERT-KO dams, but DHA did not significantly alter the expression compared to the control diet condition.