AAV9-mediated FIG4 delivery prolongs life span in Charcot-Marie-Tooth disease type 4J mouse model
Maximiliano Presa, … , Steven J. Gray, Cathleen Lutz
Maximiliano Presa, … , Steven J. Gray, Cathleen Lutz
Published April 20, 2021
Citation Information: J Clin Invest. 2021;131(11):e137159. https://doi.org/10.1172/JCI137159.
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Research Article Genetics Neuroscience

AAV9-mediated FIG4 delivery prolongs life span in Charcot-Marie-Tooth disease type 4J mouse model

Abstract

Charcot-Marie-Tooth disease type 4J (CMT4J) is caused by recessive, loss-of-function mutations in FIG4, encoding a phosphoinositol(3,5)P2-phosphatase. CMT4J patients have both neuron loss and demyelination in the peripheral nervous system, with vacuolization indicative of endosome/lysosome trafficking defects. Although the disease is highly variable, the onset is often in childhood and FIG4 mutations can dramatically shorten life span. There is currently no treatment for CMT4J. Here, we present the results of preclinical studies testing a gene-therapy approach to restoring FIG4 expression. A mouse model of CMT4J, the Fig4–pale tremor (plt) allele, was dosed with a single-stranded adeno-associated virus serotype 9 (AAV9) to deliver a codon-optimized human FIG4 sequence. Untreated, Fig4plt/plt mice have a median survival of approximately 5 weeks. When treated with the AAV9-FIG4 vector at P1 or P4, mice survived at least 1 year, with largely normal gross motor performance and little sign of neuropathy by neurophysiological or histopathological evaluation. When mice were treated at P7 or P11, life span was still significantly prolonged and peripheral nerve function was improved, but rescue was less complete. No unanticipated adverse effects were observed. Therefore, AAV9-mediated delivery of FIG4 is a well-tolerated and efficacious strategy in a mouse model of CMT4J.

Authors

Maximiliano Presa, Rachel M. Bailey, Crystal Davis, Tara Murphy, Jenn Cook, Randy Walls, Hannah Wilpan, Laurent Bogdanik, Guy M. Lenk, Robert W. Burgess, Steven J. Gray, Cathleen Lutz

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Figure 1

Neonatal delivery of AAV9-FIG4 vector improves survival of Fig4plt/plt mice.

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Neonatal delivery of AAV9-FIG4 vector improves survival of Fig4plt/plt m...
(A) Representation of the AAV9-FIG4 vector, with a full-length, codon-optimized human FIG4 cDNA (hFIG4opt) under control of the CBA promoter, including a CMV-derived enhancer and a synthetic poly(A) tail (SpA). This expression cassette was flanked by an ITR sequence for packing into AAV9. (B) Outline of preclinical study design. Fig4plt/plt mice were treated by i.c.v. injection at P1 or P4 with AAV9-FIG4, representing the presymptomatic intervention and proof-of-concept group for efficacy testing. Fig4 WT littermates were dosed i.c.v. at P1, representing the safety group for AAV9-FIG4 toxicity evaluation. Both Fig4plt/plt and WT mice treated with vehicle or untreated were included as controls. For postsymptomatic treatments, Fig4plt/plt mice were treated at P7 or P11 via i.t. injection. A minimum of n = 5 mice per sex per genotype were enrolled in each group. All mice were monitored daily for body weight and survival. Electrophysiology and behavioral assessments were conducted at various time points after AAV9-FIG4 treatment. Some of the i.c.v. injected group were analyzed at 6 to 8 months after treatment and the rest at the 12- to 13-month end point. (C) Survival and (D) average body weights (BW) for mice injected with AAV9-FIG4 via i.c.v. (5.4 × 1011 vg) at P1 and P4. For postsymptomatic intervention, Fig4plt/plt mice were treated by i.t. injection (AAV9-FIG4, 1.35 × 1012 vg) at P7 and P11. (E) Survival and (F) average body weights are shown. Dose-response analysis was conducted by injecting Fig4plt/plt mice i.t. with AAV9-FIG4 diluted 1:5 (2.7 × 1011 vg), 1:10 (1.35 × 1011 vg), and 1:100 (1.35 × 1010 vg). (G) Survival and (H) average body weights are shown. The log-rank (Mantel-Cox) test was applied for survival curve comparisons. Growth curves show average body weight ± SEM.