Altered brain structure in an ATRX-deficient mouse model of autism spectrum disorder

Mutations in the ATRX gene are a primary cause of ATR-X syndrome, which is characterized by intellectual disability, autism, and a range of brain structural abnormalities, including microcephaly. We previously showed that mice with conditional ATRX ablation in forebrain excitatory neurons display deficits in fear memory and autism-related behaviors, with some effects exhibiting sexual dimorphism. In this study, we used high-resolution magnetic resonance imaging (MRI) to systematically characterize brain structural changes associated with these behavioral abnormalities. Whole-brain analysis revealed male-specific microcephaly, while subregional analysis identified significant reductions in hippocampal structures and increased volume of the caudal cortex in mutant animals of both sexes. We also identified structural alterations in regions retaining ATRX expression, such as the thalamus, midbrain, cerebellum, and several fiber tracts. These findings suggest that ATRX loss disrupts the coordinated development of interconnected brain regions. Overall, our results implicate impaired cortico-thalamic-cerebellar connectivity as a potential neural substrate underlying the autistic-like behaviors observed in this mouse model, providing new insights into the neurobiological basis of ATR-X syndrome. LAY SUMMARYChanges in a gene called ATRX are known to affect brain development and are linked to intellectual disability and autism. In our previous work, we found that removing this gene early in brain development caused mice to show behaviors like those seen in people with autism. In this study, we used detailed brain scans to see if these behavioral changes were linked to differences in brain structure. We found that male mice without ATRX had smaller brains and bodies, while female mice did not show the same brain size reduction. However, both male and female mice had smaller areas of the brain important for memory and movement, and larger areas involved in thinking and sensing. We also saw changes in parts of the brain where ATRX was still present, suggesting that early changes in one area can affect how the whole brain develops. These findings help us understand how early disruptions in brain development might lead to autism-related behaviors.