Clinical and pathological studies of individuals diagnosed with autism spectrum disorder (ASD) have repeatedly implicated the cerebellum in ASD pathogenesis. However, previous studies of postmortem cerebellum tissue have been unsuccessful in identifying significant differences between tissue from individuals with ASD and neurotypical individuals. Notably, these previous studies primarily evaluated the transcriptional profile of granule neurons, which is the most abundant cell type in the cerebellum. However, there are multiple cell types present within the cerebellar cortex that are considerably less abundant than granule neurons and have yet to be examined regarding their relationship to ASD.

Kathleen Millen, in collaboration with Kimberly Aldinger at Seattle Children’s Hospital Research Institute, proposes to determine the cell types that are affected in the ASD cerebellum by examining all cell types that make up the cerebellar cortex. They plan to use a relatively low-cost combinatorial indexing approach to single-cell RNA-sequencing to identify all cell types in the postmortem cerebellum and compare transcriptional profiles from ASD and neurotypical individuals. Since several morphological and functional analyses have implicated Purkinje cells as the dysfunctional cell type in ASD cerebellum^1,2 the team will also use laser capture microdissection to specifically isolate Purkinje cells. High-depth RNA sequencing of Purkinje cells will allow them to account for the possibility of molecular heterogeneity between ASD individuals and define the transcriptional profile of these neurons specifically. Overall, this project aims to provide important clarification regarding the molecular and cellular diversity of the cerebellum in ASD.