SUMMARY SCA1, a fatal neurodegenerative disorder, is caused by a CAG expansion encoding a polyglutamine stretch in the protein ATXN1. We used RNA sequencing to profile cerebellar gene expression in Pcp2-ATXN1[82Q] mice with ataxia and progressive pathology and Pcp2-ATXN1[30Q]D776 animals having ataxia in absence of Purkinje cell progressive pathology. Weighted Gene Coexpression Network Analysis of the cerebellar expression data revealed two gene networks that significantly correlated with disease and have an expression profile correlating with disease progression ATXN1[82Q] Purkinje cells. The Magenta Module provides a signature of suppressed transcriptional programs reflecting disease progression in Purkinje cells, while the Lt Yellow Module, reflects transcriptional programs activated in response to disease in Purkinje cells as well as other cerebellar cell types. Furthermore, we found that upregulation of cholecystokinin (Cck) and subsequent interaction with the Cck1 receptor likely underlies the lack of progressive Purkinje cell pathology in Pcp2-ATXN1[30Q]D776 mice.

Highlights d In murine Purkinje neurons expressing ATXN1[82Q], mTORC1 signaling is depressed d In murine Purkinje neurons expressing ATXN2[127Q], mTORC1 signaling is enhanced d CCK1R activation restores Purkinje cell function/morphology and mTORC1 signaling

Spinocerebellar Ataxias (SCAs) are a group of genetic diseases characterized by progressive ataxia and neurodegeneration, often incerebellar Purkinje neurons. Mouse models of SCA Type 1 (SCA1) have been used to study molecular mechanisms underlying Purkinje neuron degeneration and death. One SCA1 mouse model, Pcp2-ATXN1[30Q]D776, has severe ataxia in absence of progressive Purkinje neuron degeneration and death. Previous RNA-seq analyses identified cerebellar up-regulation of the peptide hormone Cholecystokinin (Cck) in Pcp2-ATXN1[30Q]D776 mice. Importantly, absence of Cck1 receptor (Cck1R) in Pcp2-ATXN1[30Q]D776 mice confers a progressive disease with Purkinje neuron death. A Cck1R agonist, A71623 administered to Pcp2-ATXN1[30Q]D776;Cck-/- and Pcp2-AXTN1[82Q] mice dampened Purkinje neuron pathology and associated deficits in motor performance. In addition, A71623 administration improved motor performance of Pcp2-ATXN2[127Q] SCA2 mice. These results indicate that manipulation of the Cck-Cck1R pathway is a potential therapeutic target for treatment of diseases involving Purkinje neuron degeneration.

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