Roots of cognitive abnormalities in BTBR male mice: Brain dysmorphology, CSF flow impairment and aberrant BDNF...

This study examines neuroanatomical and molecular changes that may be responsible for cognitive impairment in the BTBR mouse model of autism. Compared to control C57Bl/6 mice, BTBR mice exhibited cognitive inflexibility, impaired in an operant learning task. MRI revealed significant brain abnormalities, including reduced cortical volume, smaller ventricles, and asymmetry in the dorsal hippocampus, accompanied by neuronal loss. BTBR mice also showed impaired cerebrospinal fluid dynamics, with reduced production and outflow. Molecular analysis revealed brain region-specific reduction in the expression of Bdnf exons 1, 2, 3, and 4 in untrained BTBR mice. Furthermore, learning induced changes in transcription of Bdnf exons exclusively in BTBR. Elevated proBDNF levels and an increased proBDNF/mature BDNF ratio in the frontal cortex and striatum indicated aberrant BDNF processing. These findings suggest that ASD-related cognitive impairments are linked to a complex of neurodevelopmental abnormalities, potentially connected to disrupted transcription, processing, and signaling of BDNF.