ABSTRACT
Spinocerebellar ataxias (SCAs) are a group of genetic diseases characterized by progressive ataxia and neurodegeneration, often in cerebellar Purkinje neurons. A SCA1 mouse model, Pcp2-ATXN1[30Q]D776, has severe ataxia in absence of progressive Purkinje neuron degeneration and death. Previous RNA-seq analyses identify cerebellar upregulation 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. Administration of a Cck1R agonist, A71623, to Pcp2-ATXN1[30Q]D776;Cck-/- and Pcp2-AXTN1[82Q] mice dampens Purkinje neuron pathology and associated deficits in motor performance. In addition, A71623 administration improves motor performance of Pcp2-ATXN2[127Q] SCA2 mice. Moreover, the Cck1R agonist A71623 corrects mTORC1 signaling and improves expression of calbindin in cerebella of AXTN1[82Q] and ATXN2[127Q] mice. These results indicate that manipulation of the Cck-Cck1R pathway is a potential therapeutic target for treatment of diseases involving Purkinje neuron degeneration.
Subject(s)
Chemokines, CC/agonists , Mechanistic Target of Rapamycin Complex 1/metabolism , Purkinje Cells/drug effects , Spinocerebellar Ataxias/drug therapy , Tetragastrin/analogs & derivatives , Animals , Ataxin-1/genetics , Ataxin-1/metabolism , Atrophy , Behavior, Animal/drug effects , Calbindins/metabolism , Chemokines, CC/genetics , Chemokines, CC/metabolism , Cholecystokinin/genetics , Cholecystokinin/metabolism , Disease Models, Animal , Female , Genetic Predisposition to Disease , Guanine Nucleotide Exchange Factors/genetics , Guanine Nucleotide Exchange Factors/metabolism , Male , Mice, Inbred C57BL , Mice, Knockout , Motor Activity/drug effects , Nerve Degeneration , Neuropeptides/genetics , Neuropeptides/metabolism , Purkinje Cells/enzymology , Purkinje Cells/pathology , Signal Transduction , Spinocerebellar Ataxias/enzymology , Spinocerebellar Ataxias/genetics , Spinocerebellar Ataxias/pathology , Tetragastrin/pharmacologyABSTRACT
Polyglutamine (polyQ) diseases are caused by expansion of translated CAG repeats in distinct genes leading to altered protein function. In spinocerebellar ataxia type 1 (SCA1), a gain of function of polyQ-expanded ataxin-1 (ATXN1) contributes to cerebellar pathology. The extent to which cerebellar toxicity depends on its cognate partner capicua (CIC), versus other interactors, remains unclear. It is also not established whether loss of the ATXN1-CIC complex in the cerebellum contributes to disease pathogenesis. In this study, we exclusively disrupt the ATXN1-CIC interaction in vivo and show that it is at the crux of cerebellar toxicity in SCA1. Importantly, loss of CIC in the cerebellum does not cause ataxia or Purkinje cell degeneration. Expression profiling of these gain- and loss-of-function models, coupled with data from iPSC-derived neurons from SCA1 patients, supports a mechanism in which gain of function of the ATXN1-CIC complex is the major driver of toxicity.