CNS-targeted base editing of the major late-onset Tay-Sachs mutation alleviates disease in mice
Maria L. Allende, Mari Kono, Y. Terry Lee, Samantha M. Olmsted, Vienna Huso, Jenna Y. Bakir, Florencia Pratto, Cuiling Li, Colleen Byrnes, Galina Tuymetova, Hongling Zhu, Cynthia J. Tifft, Richard L. Proia
Maria L. Allende, Mari Kono, Y. Terry Lee, Samantha M. Olmsted, Vienna Huso, Jenna Y. Bakir, Florencia Pratto, Cuiling Li, Colleen Byrnes, Galina Tuymetova, Hongling Zhu, Cynthia J. Tifft, Richard L. Proia
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Research Article Genetics Neuroscience

CNS-targeted base editing of the major late-onset Tay-Sachs mutation alleviates disease in mice

Abstract

Late-onset Tay-Sachs (LOTS) disease is a lysosomal storage disorder most commonly caused by a point mutation (c.805G>A) in the HEXA gene encoding the α subunit of the lysosomal enzyme β-hexosaminidase A. LOTS manifests as a range of gradually worsening neurological symptoms beginning in young adulthood. Here, we explored the efficacy of an adenine base editor (ABE) programmed with an sgRNA to correct the HEXA c.805G>A mutation. Base editing in fibroblasts from a patient with LOTS successfully converted the pathogenic HEXA c.805A to G and partially restored β-hexosaminidase activity, with minimal genome-wide off-target editing. We generated a LOTS mouse model in which the mice exhibited decreased β-hexosaminidase activity, accumulation of GM2 ganglioside in the brain, progressive neurological manifestations, and reduced lifespan. Treatment of LOTS mice with the neurotropic virus AAV-PHP.eB carrying the ABE and an sgRNA targeting the LOTS point mutation partially corrected the c.805G>A mutation in the CNS, significantly increased brain β-hexosaminidase activity, and substantially reduced GM2 ganglioside accumulation in the brain. Moreover, the therapy delayed symptom onset and significantly extended median lifespan. These findings highlight the potential of base editing as an effective treatment for LOTS and its broader applicability to other lysosomal storage disorders.

Authors

Maria L. Allende, Mari Kono, Y. Terry Lee, Samantha M. Olmsted, Vienna Huso, Jenna Y. Bakir, Florencia Pratto, Cuiling Li, Colleen Byrnes, Galina Tuymetova, Hongling Zhu, Cynthia J. Tifft, Richard L. Proia

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Figure 3

Base-editor treatment corrects the HEXA c.805G>A mutation and partially restores brain β-hexosaminidase activity in LOTS mice.

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Base-editor treatment corrects the HEXA c.805G>A mutation and partial...
(A) Schematic of ABE treatment in LOTS mice. At 6–7 weeks of age, LOTS mice were injected retro-orbitally with either AAV-PHP.eB-GFP (control) or a 1:1 mixture of AAV-PHP.eB vectors carrying v5 AAV-ABE N- and C-terminal components with LOTS-sgRNA (ABE-treated). Total dose was 2.4 × 1012 vg/mouse. Tissues were collected at 21 weeks or end of life. (B) Base editing at the HEXA c.805A site. Editing efficiency was quantified in brain, spinal cord, and liver DNA from control- and ABE-treated LOTS mice at 21 weeks using next-generation sequencing. A-to-G conversion was expressed as mean ± SD (brain: n = 18 ABE, n = 4 control; spinal cord/liver: n = 8 ABE, n = 4 control). Each dot represents 1 mouse. ****P < 0.0001 by 1-way ANOVA with Bonferroni’s correction. (C and D) Heatmaps of A-to-G conversion across the ABE editing window in brain (C) and spinal cord (D) from ABE-treated mice. Each row represents 1 mouse. Protospacer sequence is shown above; uppercase: exon, lowercase: intron. (E) β-Hexosaminidase activity in brain lysates from 21-week-old WT, control-treated LOTS, and ABE-treated LOTS mice. α subunit–specific activity is expressed as a percentage of WT (set at 100%). Mean ± SD shown (n = 4 per group, males). **P < 0.01 by Student’s t test. Partially created with BioRender.com.