Treatment of Huntington’s disease with a pan-HTT-targeting CRISPR nuclease

Sep 30, 2026

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Huntington's disease (HD) is an inherited neurodegenerative disorder driven by expansion of a CAG trinucleotide repeat in the huntingtin (HTT) gene, producing mutant protein that progressively destroys neurons. With no approved disease-modifying therapy, a pan-HTT-targeting CRISPR-Cas9 approach is developed. Delivered to mouse striatum via AAV5, it reduces mutant HTT mRNA and protein by 55–80% through frameshift-inducing indels in HTT exon 1, improving motor function, behavior, and striatal pathology while limiting inclusion formation. In Hu21/21 mice it lowers HTT protein by 44% without measurable behavioral deficits or neuronal viability loss, though neuroinflammation is observed.

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CategoryHealthcare

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Abstract

Introduction

bioRxiv preprint doi: [https://doi.org/10.64898/2025.12.20.695720](https://doi.org/10.64898/2025.12.20.695720); this version posted December 22, 2025. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Treatment of Huntington’s disease with a pan-HTT-targeting CRISPR nuclease Katherine Tan 1, Daniela Del Bosque Siller2, Alisha Y. Xiong2, Anna X.A. Wang 1, Tristan X. McCallister 1, Sreya Mummadi2, Luke A. St John2, Tae Kyu Lee 1, Annika Carrillo 1, Daniel G. Renshaw 1, Richard H. Zhou 1, Colin K.W. Lim 1, Jack He 1, Christopher J. Fields3, Michael R. Hayden4,5,6, and Thomas Gaj 1,7 1 Department of Bioengineering, Grainger College of Engineering, University of Illinois UrbanaChampaign, Urbana, IL 61801, USA 2 School of Molecular and Cellular Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA 3 High-Performance Biological Computing, Roy J. Carver Biotechnology Center, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA 4 Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC V5Z 4H4, CA 5 BC Children’s Hospital Research Institute, University of British Columbia, Vancouver, BC V5Z 4H4, CA 6 Department of Medical Genetics, University of British Columbia, Vancouver, BC V6T 1Z3, CA 7 Carl R. Woese Institute for Genomic Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA Correspondence: Thomas Gaj, Department of Bioengineering, University of Illinois UrbanaChampaign, Urbana, IL 61801, USA. Email: [gaj@illinois.edu](gaj@illinois.edu) bioRxiv preprint doi: [https://doi.org/10.64898/2025.12.20.695720](https://doi.org/10.64898/2025.12.20.695720); this version posted December 22, 2025. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. ABSTRACT Huntington's disease (HD) is an inherited neurodegenerative disorder caused by an expansion of a CAG trinucleotide repeat in the huntingtin (HTT) gene, which leads to a mutant protein that destroys neurons in the brain. Despite intense effort, there remains no approved disease-modifying therapy for HD. Here we develop a pan-HTT-targeting CRISPR-Cas9 system that, when delivered to the striatum ofR6/2 and YAC128 mice by AAV5, lowered mutant HTT mRNA and protein by 55-80% via its induction of frameshift-inducing indel mutations in HTTexon 1. Cas9 targeting improved motor coordination and locomotor activity, decreased anxietylike deficits, reduced clasping and weight loss, limited striatal atrophy, and decreased the formation of intranuclear inclusions immunoreactive for the mutant HTT protein. In Hu21/21 mice, which carry the wild-type human HTT gene in lieu of the mouse ortholog, Cas9 lowered the HTT protein by 44% but induced no measurable behavioral deficits and had no adverse effect on neuronal viability, though its targeting was associated with neuroinflammation. Altogether, our results demonstrate the ability for a newly developed pan-HTT-targeting Cas9 system to affect HD-related phenotypes across models and provides insights into its tolerability. bioRxiv preprint doi: [https://doi.org/10.64898/2025.12.20.695720](https://doi.org/10.64898/2025.12.20.695720); this version posted December 22, 2025. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. INTRODUCTION Huntington's disease (HD) is a dominantly inherited and fatal neurodegenerative disorder characterized by severe motor, cognitive an

FAQs

What causes Huntington's disease in the document?

HD is caused by expansion of a CAG trinucleotide repeat within exon 1 of the HTT gene, leading to an elongated polyglutamine tract that increases misfolding and aggregation and results in neurotoxicity and neuron loss.

What is the core therapy approach described?

The work develops a pan-HTT-targeting CRISPR-Cas9 system designed to induce frameshift-inducing indel mutations in HTT exon 1 to lower mutant HTT mRNA and protein.

How did the CRISPR-Cas9 system perform in mouse models?

In R6/2 and YAC128 mice, AAV5-delivered Cas9 reduced mutant HTT mRNA/protein by 55–80% and improved motor coordination and activity while reducing anxiety-like deficits, clasping, weight loss, striatal atrophy, and mutant HTT inclusions.

What were the observed effects in Hu21/21 mice?

In Hu21/21 mice, Cas9 lowered HTT protein by 44% but produced no measurable behavioral deficits and no adverse effect on neuronal viability; targeting was associated with neuroinflammation.

Sep 30, 2026

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