Cross-species genetic screens identify transglutaminase 5 as a regulator of polyglutamine-expanded ataxin-1
Won-Seok Lee, … , Juan Botas, Huda Y. Zoghbi
Won-Seok Lee, … , Juan Botas, Huda Y. Zoghbi
Published May 2, 2022
Citation Information: J Clin Invest. 2022;132(9):e156616. https://doi.org/10.1172/JCI156616.
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Research Article Genetics Neuroscience

Cross-species genetic screens identify transglutaminase 5 as a regulator of polyglutamine-expanded ataxin-1

Abstract

Many neurodegenerative disorders are caused by abnormal accumulation of misfolded proteins. In spinocerebellar ataxia type 1 (SCA1), accumulation of polyglutamine-expanded (polyQ-expanded) ataxin-1 (ATXN1) causes neuronal toxicity. Lowering total ATXN1, especially the polyQ-expanded form, alleviates disease phenotypes in mice, but the molecular mechanism by which the mutant ATXN1 is specifically modulated is not understood. Here, we identified 22 mutant ATXN1 regulators by performing a cross-species screen of 7787 and 2144 genes in human cells and Drosophila eyes, respectively. Among them, transglutaminase 5 (TG5) preferentially regulated mutant ATXN1 over the WT protein. TG enzymes catalyzed cross-linking of ATXN1 in a polyQ-length–dependent manner, thereby preferentially modulating mutant ATXN1 stability and oligomerization. Perturbing Tg in Drosophila SCA1 models modulated mutant ATXN1 toxicity. Moreover, TG5 was enriched in the nuclei of SCA1-affected neurons and colocalized with nuclear ATXN1 inclusions in brain tissue from patients with SCA1. Our work provides a molecular insight into SCA1 pathogenesis and an opportunity for allele-specific targeting for neurodegenerative disorders.

Authors

Won-Seok Lee, Ismael Al-Ramahi, Hyun-Hwan Jeong, Youjin Jang, Tao Lin, Carolyn J. Adamski, Laura A. Lavery, Smruti Rath, Ronald Richman, Vitaliy V. Bondar, Elizabeth Alcala, Jean-Pierre Revelli, Harry T. Orr, Zhandong Liu, Juan Botas, Huda Y. Zoghbi

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Figure 7

TG5 but not TG2 colocalizes with nuclear inclusions of ATXN1 in the pons of patients with SCA1.

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TG5 but not TG2 colocalizes with nuclear inclusions of ATXN1 in the pons...
(A) Representative IF images of ATXN1 nuclear inclusions (NIs) in the MAP2+ neurons that have large nuclei in the control and SCA1 patient pons. Scale bar: 50 μm. (B) Representative IF images of TG5 (left) and TG2 (right) in the neurons that display ATXN1 NIs in the pons of patients with SCA1. Control pons were also stained for comparison. White dashed-line boxes in the top images are enlarged in the bottom. Scale bar: 25 μm in the top images; 10 μm in the bottom images. (C) Quantification of the proportion of ATXN1 NIs that colocalize with TG. Images were obtained from 3 controls and 3 patients with SCA1, and the proportion was calculated from 20–30 NIs in each individual. Data shown as mean ± SD, ****P < 0.0001, 2-tailed t test. (D) Representative IF images of TG5 (left) and TG2 (right) in the CALB1+ Purkinje cells in control and SCA1 patient cerebellum. White dashed-line boxes in the middle images are enlarged in the bottom. Scale bar: 50 μm in the top and middle images; 20 μm in the bottom images. (E) Quantification of the proportion of Purkinje cells with nuclear TG. Images were obtained from 3 controls and 3 patients with SCA1, and the proportion was calculated from 18–24 Purkinje cells in each individual. Data shown as mean ± SD, **P < 0.01, ***P < 0.001, 2-way ANOVA, post hoc Tukey’s test.