Early Behavioral Alterations and Increased Expression of Endogenous Retroviruses Are Inherited Across Generations in Mice Prenatally Exposed to Valproic Acid

Abstract

Prenatal treatment with the antiepileptic drug valproic acid (VPA) is associated with a significant risk of somatic anomalies, neurodevelopmental delays, and 7-10× increase in the incidence of autism spectrum disorders (ASD) in children. Rodents exposed to VPA in pregnancy show birth defects, deficits in neurodevelopment, and cognitive/social anomalies resembling those of ASD children. Mechanisms of VPA neurobehavioral toxicity are still unclear but as VPA is a non-selective inhibitor of histone deacetylases, epigenetic modifications are likely involved. This study was aimed to evaluate the transgenerational impact of prenatal VPA exposure on mouse early behavioral development, studying F, F, and F generations after VPA challenge on gestational day (GD) 10.5. We also analyzed in brain and in peripheral blood mononuclear cells the expression levels of different endogenous retrovirus (ERV) families, potential biomarkers of derailed brain development, since human ERVs have been implicated in the pathogenesis of neurodevelopmental disorders (NDDs) such as ASD. Somatic effects of VPA were evident only in F generation and more markedly in the female sex. Across F and F generations, VPA delayed righting reflex, increased motor activity, and reduced ultrasonic vocalizations. The behavioral changes in F are milder though in the same direction. VPA increased expression of most ERVs across the three generations in brain and blood. In utero VPA induced neurodevelopmental alterations more marked in the maternal lineage that persisted also in F, suggesting ERVs as possible downstream effectors of the VPA epigenetic alterations.

A Systematic Review of the Valproic-Acid-Induced Rodent Model of Autism

“…In studies where both female and male test subjects were employed, VPA-exposed males showed more robust social impairments than VPA females, suggesting a potential protective/ compensatory effect towards social impairment induction in females [55]. In addition, VPA-exposed females (compared to VPA-exposed males) were more likely to exhibit stereotypies occurring earlier in the open field testing session [56,57] elicit shorter distress-call durations in the ultrasonic vocalisation test [31,58], and commit more T-maze errors in the T/Y-maze test for cognitive rigidity [53]. In contrast, VPA-exposed males demonstrated a greater reduction in social preference (in the social preference test), social novelty preference (in the social novelty preference test), more stereotypies, more play-fighting in adulthood (in the social interaction test), and delayed T-maze acquisition-phase performance (in trained versions).…”

Translational Outcomes Relevant to Neurodevelopmental Disorders Following Early Life Exposure of Rats to Chlorpyrifos

“…Reduced USV communication has been discovered in many genetic rat models of NDD, including those with mutations in synaptic genes, such as Shank3, cellular housekeeping genes such as ubiquitin ligase Ube3a that causes Angelman Syndrome, and the calcium channel gene Cacna1c (Berg et al 2018;Berg et al 2020;Kisko et al 2018), as well as numerous genetic mouse models of NDD, including 16p11.2 deletion syndrome (Yang et al 2015), the Ca(V)1.2 L-type calcium channel gene that causes Timothy Syndrome (Bader et al 2011), synaptic genes such as neuroligins (Wöhr et al 2013), and high con dence ASD candidate genes, such as Tbx1 (Hiramoto et al 2011). Reduced USV communication has also been reported in models of environmentally-induced NDD phenotypes, including maternal immune activation (Schwartzer et al 2013) and prenatal exposure to valproic acid (Moldrich et al 2013;Tartaglione et al 2019). While we exposed rats to CPF during the rst days of postnatal life, our ndings are consistent with earlier literature showing that exposure to CPF during the gestational period resulted in altered behavioral and physical development in rodent pups in a sex-dependent manner.…”

Pregnancy drugs, fetal germline epigenome, and risks for next‐generation pathology: A call to action

“…Also in mice, F0 VPA resulted in altered transcriptional activity in whole embryos, blood, and brain samples of F2, and higher proinflammatory cytokines, with more marked transcriptional effects in offspring from F1 females (Cipriani et al ). F0 VPA was also found to affect F2 phenotype, including a delayed righting reflex, increased motor activity, and reduced ultrasonic vocalizations in mice (Tartaglione et al ).…”