Abnormal axon guidance signals and reduced interhemispheric connection via anterior commissure in neonates of marmoset ASD model.

In autism spectrum disorder (ASD), disrupted functional and structural connectivity in the social brain has been suggested as the core biological mechanism underlying the social recognition deficits of this neurodevelopmental disorder. In this study, we aimed to identify genetic and neurostructural abnormalities at birth in a non-human primate model of ASD, the common marmoset with maternal exposure to valproic acid (VPA), which has been reported to display social recognition deficit in adulthood. Using a comprehensive gene expression analysis, we found that 20 genes were significantly downregulated in VPA-exposed neonates. Of these, Frizzled3 (FZD3) and PIK3CA were identified in an axon guidance signaling pathway. FZD3 is essential for the normal development of the anterior commissure (AC) and corpus callosum (CC); hence, we performed diffusion tensor magnetic resonance imaging with a 7-Tesla scanner to measure the midsagittal sizes of these structures. We found that the AC size in VPA-exposed neonates was significantly smaller than that in age-matched controls, while the CC size did not differ. These results suggest that downregulation of the genes related to axon guidance and decreased AC size in neonatal primates may be linked to social brain dysfunctions that can happen later in life.