Early environmental enrichment for autism spectrum disorder Fmr1 mice models has positive behavioral and molecular effects

Autism spectrum disorder is a complex neurodevelopmental condition with genetic and phenotypic heterogeneity characterized by hallmark impairments in social functioning and repetitive behaviors. Fragile X syndrome (FXS), the leading single-gene form of autism spectrum disorder, is the most common form of inherited intellectual disability. Environmental enrichment has been shown to improve several aspects of brain development and affect histopathological, cognitive, and behavioral outcomes. However, the optimal time window to initiate it and improve cognitive and emotional development is largely unexplored. In the current study, we determined the longitudinal trends of BDNF-TrkB expression and dendritic development in FXS mice. Additionally, FXS mice were housed in an enriched environment when they showed significantly different BDNF-TrkB pathways and the phenotype of dendritic spines on postnatal day 10 (P10) until P60. The environmental enrichment delayed and attenuated some neurological alterations in FXS mice and prevented the development of cognitive and anxiety-related abnormalities and repetitive stereotyped behaviors. The correlation between neurotrophin-related pathways and multiple autistic-like behaviors was confirmed. Transcriptional profiling indicates that environmental enrichment increases the differences in the prefrontal cortex and hippocampal gene expression associated with the neural system and behavioral development. Our results provide novel evidence on the usefulness of early intervention for neurodevelopmental disorders as a strategy to facilitate positive effects on neural development and behaviors by acting on the BDNF/TrkB-PLCγ1-CaMKII pathway.