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 2

AAV9-FIG4 therapy restores FIG4 protein levels and behavioral outcomes of Fig4plt/plt mice.

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AAV9-FIG4 therapy restores FIG4 protein levels and behavioral outcomes o...
FIG4 protein levels were assessed in whole-protein lysates from brain and spinal cord by Western blot. Mice treated at P1 or P4 by i.c.v. injection of the maximum AAV9-FIG4 dose were analyzed at 6 months of age. (A) Representative Western blot showing detection of FIG4 as a single band at 112 kDa, present in Fig4+/+ untreated mice (lane 1), Fig4+/+ treated at P1 (lane 2), Fig4plt/plt treated at P1 (lane 3), Fig4plt/plt treated at P4 (lane 4), and not present in Fig4plt/plt untreated mice (lane 5). (B) FIG4 levels were normalized to GAPDH as a loading control, and RFC calculated using Fig4+/+ untreated mice as reference. (C) Average RFC at 100–120 days of age for i.t. treated mice at P7 with maximum or 1:5 diluted AAV9-FIG4. (D–F) Fig4plt/plt mice treated by i.t. delivery at P7 with AAV9-FIG4 (1:5 dilution, 2.7 × 1011 vg) were assessed 35 days after treatment for motor coordination performance, grip strength, and general activity. (D) Rotarod analysis is reported as the latency to fall during 3 trials. (E) Average grip strength normalized to body weight in the forepaws and all paws is shown. (F) General activity was assessed by monitoring voluntary wheel running; the average total distance traveled at each day time cycle is reported. Data are represented as average ± SEM of combined males and females, since no significant differences were observed by sex. Groups were compared by 2-way ANOVA with Dunnett’s correction for multiple comparisons (B and C) and Mann-Whitney U test (D–F). *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.