<i>CASP8</i> intronic expansion identified by poly-glycine-arginine pathology increases Alzheimer’s disease risk

Alzheimer's disease (AD) affects more than 10% of the population ≥65 y of age, but the underlying biological risks of most AD cases are unclear. We show anti-poly-glycine-arginine (a-polyGR) positive aggregates frequently accumulate in sporadic AD autopsy brains (45/80 cases). We hypothesize that these aggregates are caused by one or more polyGR-encoding repeat expansion mutations. We developed a CRISPR/deactivated-Cas9 enrichment strategy to identify candidate GR-encoding repeat expansion mutations directly from genomic DNA isolated from a-polyGR(+) AD cases. Using this approach, we isolated an interrupted (GGGAGA)<sub>n</sub> intronic expansion within a SINE-VNTR-Alu element in <i>CASP8</i> (<i>CASP8</i>-GGGAGA<sup>EXP</sup>). Immunostaining using a-polyGR and locus-specific C-terminal antibodies demonstrate that the <i>CASP8</i>-GGGAGA<sup>EXP</sup> expresses hybrid poly(GR)n(GE)n(RE)n proteins that accumulate in <i>CASP8</i>-GGGAGA<sup>EXP</sup>(+) AD brains. In cells, expression of <i>CASP8</i>-GGGAGA<sup>EXP</sup> minigenes leads to increased p-Tau (Ser202/Thr205) levels. Consistent with other types of repeat-associated non-AUG (RAN) proteins, poly(GR)n(GE)n(RE)n protein levels are increased by stress. Additionally, levels of these stress-induced proteins are reduced by metformin. Association studies show specific aggregate promoting interrupted <i>CASP8</i>-GGGAGA<sup>EXP</sup> sequence variants found in ~3.6% of controls and 7.5% AD cases increase AD risk [<i>CASP8</i>-GGGAGA-AD-R1; OR 2.2, 95% CI (1.5185 to 3.1896), <i>P</i> = 3.1 × 10<sup>-5</sup>]. Cells transfected with a high-risk <i>CASP8</i>-GGGAGA-AD-R1 variant show increased toxicity and increased levels of poly(GR)n(GE)n(RE)n aggregates. Taken together, these data identify polyGR(+) aggregates as a frequent and unexpected type of brain pathology in AD and <i>CASP8</i>-GGGAGA-AD-R1 alleles as a relatively common AD risk factor. Taken together, these data support a model in which <i>CASP8</i>-GGGAGA<sup>EXP</sup> alleles combined with stress increase AD risk.

Authors

Institutions

Publication Details

Journal
Proceedings of the National Academy of Sciences
Published
2025-02-12
DOI
https://doi.org/10.1073/pnas.2416885122
Citations
7
Primary Topic
Genetic Neurodegenerative Diseases
Type
article
Field-Weighted Citation Impact
6.36

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

CASP8 intronic expansion identified by poly-glycine-arginine pathology increases Alzheimer’s disease risk

Mónica Báñez-Coronel, Lien Nguyen, Eric T. Wang, Javier Redding‐Ochoa et al.
7 citations
Proceedings of the National Academy of Sciences
Genetic Neurodegenerative Diseases
6.36
article

CASP8 intronic expansion identified by poly-glycine-arginine pathology increases Alzheimer’s disease risk

Mónica Báñez-Coronel, Lien Nguyen, Eric T. Wang, Javier Redding‐Ochoa, Alan E. Renton, Evangelos Nizamis, Kiruphagaran Thangaraju, Ramadan Ajredini, Laura P.W. Ranum, Chase P. Kelley, Lisa E. L. Romano, Theresa R. Connors, Beverly L. Davidson, Shu Guo, Angelica Gaona, Todd Eliot Golde, Paul N. Valdmanis, Bradley T. Hyman, Tao Zu, Olga Pletniková, Paul T. Ranum, Stefan Prokop, Xiang‐Yang Lou, Anthony T. Yachnis, Alison Goate, Alexandra Melloni, H. Brent Clark, Logan Bell, Juan C. Troncoso, Rodrigo F. Tomas
article en
7 citations

Abstract

Alzheimer's disease (AD) affects more than 10% of the population ≥65 y of age, but the underlying biological risks of most AD cases are unclear. We show anti-poly-glycine-arginine (a-polyGR) positive aggregates frequently accumulate in sporadic AD autopsy brains (45/80 cases). We hypothesize that these aggregates are caused by one or more polyGR-encoding repeat expansion mutations. We developed a CRISPR/deactivated-Cas9 enrichment strategy to identify candidate GR-encoding repeat expansion mutations directly from genomic DNA isolated from a-polyGR(+) AD cases. Using this approach, we isolated an interrupted (GGGAGA)<sub>n</sub> intronic expansion within a SINE-VNTR-Alu element in <i>CASP8</i> (<i>CASP8</i>-GGGAGA<sup>EXP</sup>). Immunostaining using a-polyGR and locus-specific C-terminal antibodies demonstrate that the <i>CASP8</i>-GGGAGA<sup>EXP</sup> expresses hybrid poly(GR)n(GE)n(RE)n proteins that accumulate in <i>CASP8</i>-GGGAGA<sup>EXP</sup>(+) AD brains. In cells, expression of <i>CASP8</i>-GGGAGA<sup>EXP</sup> minigenes leads to increased p-Tau (Ser202/Thr205) levels. Consistent with other types of repeat-associated non-AUG (RAN) proteins, poly(GR)n(GE)n(RE)n protein levels are increased by stress. Additionally, levels of these stress-induced proteins are reduced by metformin. Association studies show specific aggregate promoting interrupted <i>CASP8</i>-GGGAGA<sup>EXP</sup> sequence variants found in ~3.6% of controls and 7.5% AD cases increase AD risk [<i>CASP8</i>-GGGAGA-AD-R1; OR 2.2, 95% CI (1.5185 to 3.1896), <i>P</i> = 3.1 × 10<sup>-5</sup>]. Cells transfected with a high-risk <i>CASP8</i>-GGGAGA-AD-R1 variant show increased toxicity and increased levels of poly(GR)n(GE)n(RE)n aggregates. Taken together, these data identify polyGR(+) aggregates as a frequent and unexpected type of brain pathology in AD and <i>CASP8</i>-GGGAGA-AD-R1 alleles as a relatively common AD risk factor. Taken together, these data support a model in which <i>CASP8</i>-GGGAGA<sup>EXP</sup> alleles combined with stress increase AD risk.

Proceedings of the National Academy of SciencesVol. 122(7)
University of Minnesota (US), Allen Institute for Brain Science (US), Children's Hospital of Philadelphia (US), Johns Hopkins University (US), Johns Hopkins Medicine (US), University of Washington Medical Center (US), University of Florida (US), Massachusetts General Hospital (US), MaineGeneral Medical Center (US), University of Pennsylvania (US), Philadelphia University (US), Icahn School of Medicine at Mount Sinai (US)
U.S. Department of Defense, McKnight Foundation, Johns Hopkins University, National Institutes of Health, U.S. Army, National Institute on Aging, National Institute of Neurological Disorders and Stroke
Good health and well-being
Openalex Percentile: Top 3%
Genetic Neurodegenerative Diseases
6.36
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.