Cerebellar structure and function abnormalities in 16p11.2 microduplication mice.

16p11.2 microduplication (16p11.2dp/+) is associated with neuropsychiatric disorders including schizophrenia, autism and intellectual disability. Cerebellar abnormalities have been implicated in these disorders. In 16p11.2dp/+ mice, the cerebellum displays significant transcriptional dysregulation, and humans with 16p11.2 microduplication have decreased cerebellar volume. Despite this, cerebellar anatomy and cerebellar-dependent behaviour in 16p11.2dp/+ mice remain uncharacterized. To address this, we histologically examined the cerebellar cortex in 16p11.2dp/+ mice. There were no structural differences in cerebellar lobule IV/V or impairments in gait or motor coordination, commonly associated with lobule IV/V. In contrast, more Purkinje cells (PCs) were mislocalized to the granule layer and parvalbumin expression was decreased in molecular layer interneurons (MLIs) in cerebellar lobule VI of 16p11.2dp/+ mice, but not in lobule IV/V. Cerebellar lobule VI is associated with delay eyeblink conditioning, and 16p11.2dp/+ mice are impaired in cerebellum-dependent associative learning on this task. Specifically, 16p11.2dp/+ mice had conditioned response (CR) percentage and CR onset latency deficits, suggesting lobule-specific alterations to PC localization and MLI parvalbumin expression may impair learning and adaptive timing of cerebellar-driven CRs. Similarly, schizophrenia involves CR acquisition deficits in delay eyeblink conditioning. Further investigation of the cerebellum in 16p11.2dp/+ mice may provide insights into the pathogenesis of neuropsychiatric disorders linked to this copy number variant.