A second hit approach using early life seizures in Fmr1 knockout mice induces autism-like behavioral deficits.

Fragile X syndrome (FXS) is the leading monogenetic cause of autism spectrum disorder (ASD) and expresses a high rate of seizures. Individuals with epilepsy also have a high rate of ASD. To disentangle the effects of FXS and early-life seizures on later behavioral deficits, we examined the impact of repeated seizures on the behavior and molecular changes in Fmr1 knockout (KO) male mice and wild-type (WT) male mice, serving as a model of FXS. A high seizure load was accomplished through three flurothyl-induced tonic-clonic seizures per day across postnatal days (PD) 7-11. In adulthood, mice were assessed in a battery of behavioral tasks to assess long-term behavioral deficits. A high seizure load decreased exploratory behavior and activity in both KO and control mice. Genotypic differences were observed with KO mice expressing significantly more repetitive and anxiety-like behavior. Early-life seizures in KO mice significantly decreased locomotor activity and increased associative learning, The double hit of FMR1 knockout and seizures resulted in a potentiation of repetitive behavior in the nose poke test. Following western blot analysis, we found no significant effects of genotype or treatment on mTOR signaling proteins, neuroinflammatory markers, or ion channel proteins. A high seizure load shows to have detrimental effects singularly and did exacerbate behavioral deficits in the mice with Fmr1 deletion. These findings further illuminate the long-term effects of early-life seizures, the impact of the FMR1 deletion, and the impact of two hits on the developing brain.