Modulation of ATXN1 S776 phosphorylation reveals the importance of allele-specific targeting in SCA1
Larissa Nitschke, Stephanie L. Coffin, Eder Xhako, Dany B. El-Najjar, James P. Orengo, Elizabeth Alcala, Yanwan Dai, Ying-Wooi Wan, Zhandong Liu, Harry T. Orr, Huda Y. Zoghbi
Larissa Nitschke, Stephanie L. Coffin, Eder Xhako, Dany B. El-Najjar, James P. Orengo, Elizabeth Alcala, Yanwan Dai, Ying-Wooi Wan, Zhandong Liu, Harry T. Orr, Huda Y. Zoghbi
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Research Article Genetics Neuroscience

Modulation of ATXN1 S776 phosphorylation reveals the importance of allele-specific targeting in SCA1

Abstract

Spinocerebellar ataxia type 1 (SCA1) is an adult-onset neurodegenerative disorder characterized by motor incoordination, mild cognitive decline, respiratory dysfunction, and early lethality. It is caused by the expansion of the polyglutamine (polyQ) tract in Ataxin-1 (ATXN1), which stabilizes the protein, leading to its toxic accumulation in neurons. Previously, we showed that serine 776 (S776) phosphorylation is critical for ATXN1 stability and contributes to its toxicity in cerebellar Purkinje cells. Still, the therapeutic potential of disrupting S776 phosphorylation on noncerebellar SCA1 phenotypes remains unstudied. Here, we report that abolishing S776 phosphorylation specifically on the polyQ-expanded ATXN1 of SCA1-knockin mice reduces ATXN1 throughout the brain and not only rescues the cerebellar motor incoordination but also improves respiratory function and extends survival while not affecting the hippocampal learning and memory deficits. As therapeutic approaches are likely to decrease S776 phosphorylation on polyQ-expanded and WT ATXN1, we further disrupted S776 phosphorylation on both alleles and observed an attenuated rescue, demonstrating a potential protective role of WT allele. This study not only highlights the role of S776 phosphorylation to regulate ATXN1 levels throughout the brain but also suggests distinct brain region–specific disease mechanisms and demonstrates the importance of developing allele-specific therapies for maximal benefits in SCA1.

Authors

Larissa Nitschke, Stephanie L. Coffin, Eder Xhako, Dany B. El-Najjar, James P. Orengo, Elizabeth Alcala, Yanwan Dai, Ying-Wooi Wan, Zhandong Liu, Harry T. Orr, Huda Y. Zoghbi

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Figure 2

Disruption of S776 phosphorylation reduces polyQ-expanded ATXN1[154Q] levels in the cerebellum, brainstem, and hippocampus.

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Disruption of S776 phosphorylation reduces polyQ-expanded ATXN1[154Q] le...
(A) Sanger sequencing confirming serine-to-alanine mutation at position 776 and synonymous mutations in heterozygous Atxn1154Q[S776A]/2Q F1 offspring upon CRISPR injections. (B) Genotyping of F1 offspring using specific primers to distinguish WT and SCA1 mice as well as primers for the detection of the S776A allele. Representative Western blots and quantifications of ATXN1[2Q] and ATXN1[154Q] protein levels in the (C) cerebellum, (D) brainstem, and (E) hippocampus of 6-week-old Atxn1154Q/2Q (SCA1) and Atxn1154Q[S776A]/2Q (SCA1 S776A) mice. For each assay, a minimum of 6 replicates were performed. Simple comparisons used Student’s t test. *P < 0.05. All data represent means ± SEM.