Neuroanatomical analysis of the BTBR mouse model of autism using magnetic resonance imaging and diffusion tensor imaging

Autism is a neurodevelopmental disorder characterized by abnormal reciprocal social interactions, communication deficits, and repetitive behaviours with restricted interests. Autism-relevant phenotypes in the inbred mouse strain BTBR T+tf/J (BTBR) offer translational tools to discover biological mechanisms underlying unusual mouse behaviours analogous to symptoms of autism. Two of the most consistent findings with BTBR are lack of sociability as measured by the three-chamber social approach task and increased amount of time engaged in self-grooming in an empty cage. Here we evaluated BTBR as compared to two typical inbred strains with high sociability and low self-grooming, C57BL/6J (B6) and FVB/AntJ (FVB), on both the automated three-chambered social approach task and repetitive self-grooming assays. Brains from the behaviourally tested mice were analyzed using magnetic resonance imaging and diffusion tensor imaging to investigate potential neuroanatomical abnormalities throughout the brain; specifically, to discover neuroanatomical mechanisms which could explain the autism-relevant behavioural abnormalities. Significant differences in volume and white matter microstructure were detected in multiple anatomical regions throughout the brain of BTBR compared to B6 and FVB. Further, significant correlations were found between behavioural measures and areas of the brain known to be associated with those behaviours. For example, striatal volume was strongly correlated to time spent in self-grooming across strains. Our findings suggest that neuropathology exists in BTBR beyond the previously reported white matter abnormalities in the corpus callosum and hippocampal commissure and that these brain differences may be related to the behavioural abnormalities seen in BTBR.