A Neural Basis for Mutant ATAXIN-1 Induced Respiratory Dysfunction in Mouse Models of Spinocerebellar Ataxia Type 1

Spinocerebellar ataxia type 1 (SCA1), a dominantly inherited neurodegenerative disorder caused by an expanded trinucleotide repeat in the ATAXIN-1 (ATXN1) gene, is characterized by motor dysfunction, cognitive impairment, and death from compromised swallowing and respiration. To delineate specific cell types that contribute to respiratory dysfunction, we utilized the floxed conditional knock-in f-ATXN1 ^146Q/2Q mouse. Whole body plethysmography during spontaneous respiration and respiratory challenge showed that f-ATXN1 ^146Q/2Q mice exhibit a spontaneous respiratory phenotype characterized by elevated respiratory frequency, volumes, and respiratory output. Consequently, the ability of f-ATXN1 ^146Q/2Q mice to increase ventilation during the challenge is impaired. To investigate the role of mutant ATXN1 expression in neural and skeletal muscle lineages, f-ATXN1 ^146Q/2Q mice were bred to Nestin-Cre and Acta1-Cre mice respectively. These analyses revealed that the abnormal spontaneous respiration in f-ATXN1 ^146Q/2Q mice involved two aspects: a behavioral phenotype in which SCA1 mice exhibit increased motor activity during respiratory testing and functional dysregulation of central respiratory control centers. Both aspects of spontaneous respiration were partially ameliorated by removing mutant ATXN1 from neural, but not skeletal muscle, cell lineages.