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

CNS pathology is reduced in AAV9-FIG4–treated Fig4plt/plt mice.

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CNS pathology is reduced in AAV9-FIG4–treated Fig4plt/plt mice. Histopat...
Histopathology changes were assessed in i.c.v. and i.t. AAV9-FIG4–treated and untreated Fig4plt/plt mice and WT controls. (A) Representative H&E images of motor cortex, thoracic spinal cord (ventral horn), and DRGs dissected from the indicated groups. Scale bars: 50 μm. Black arrows indicate cytoplasmic vacuoles. (B) Representative semithin sections of toluidine blue–stained sciatic nerve were analyzed for axon size distribution. Cross sections of sciatic nerve were scanned at ×40, and axon caliber for each axon in the section was determined using ImageJ software. (C) Distribution of the average axon frequency by size (axon area, 50 μm). (D and E) The autophagosome marker SQSTM1 (p62) and the astrocyte marker GFAP were analyzed by quantitative Western blot in protein lysates of brain (BR) and spinal cord (SC). p62 and GFAP signal were normalized to GAPDH loading control. RFC was calculated using Fig4+/+ untreated tissue as reference. Fig4plt/plt–derived protein extracts were prepared from 23-day-old untreated mice. Bars represent the average ± SEM. Statistical significance was calculated by 1-way ANOVA with Dunnett’s test correction for multiple comparisons. *P < 0.05; **P < 0.01; ***P < 0.001.