Gene replacement therapy in a model of Charcot-Marie-Tooth 4C neuropathy

Brain. 2019 May 1;142(5):1227-1241. doi: 10.1093/brain/awz064.

Abstract

Charcot-Marie-Tooth disease type 4C is the most common recessively inherited demyelinating neuropathy that results from loss of function mutations in the SH3TC2 gene. Sh3tc2-/- mice represent a well characterized disease model developing early onset progressive peripheral neuropathy with hypo- and demyelination, slowing of nerve conduction velocities and disturbed nodal architecture. The aim of this project was to develop a gene replacement therapy for treating Charcot-Marie-Tooth disease type 4C to rescue the phenotype of the Sh3tc2-/- mouse model. We generated a lentiviral vector LV-Mpz.SH3TC2.myc to drive expression of the human SH3TC2 cDNA under the control of the Mpz promoter specifically in myelinating Schwann cells. The vector was delivered into 3-week-old Sh3tc2-/- mice by lumbar intrathecal injection and gene expression was assessed 4-8 weeks after injection. Immunofluorescence analysis showed presence of myc-tagged human SH3TC2 in sciatic nerves and lumbar roots in the perinuclear cytoplasm of a subset of Schwann cells, in a dotted pattern co-localizing with physiologically interacting protein Rab11. Quantitative PCR analysis confirmed SH3TC2 mRNA expression in different peripheral nervous system tissues. A treatment trial was initiated in 3 weeks old randomized Sh3tc2-/- littermate mice which received either the full or mock (LV-Mpz.Egfp) vector. Behavioural analysis 8 weeks after injection showed improved motor performance in rotarod and foot grip tests in treated Sh3tc2-/- mice compared to mock vector-treated animals. Moreover, motor nerve conduction velocities were increased in treated Sh3tc2-/- mice. On a structural level, morphological analysis revealed significant improvement in g-ratios, myelin thickness, and ratios of demyelinated fibres in lumbar roots and sciatic nerves of treated Sh3tc2-/- mice. Finally, treated mice also showed improved nodal molecular architecture and reduction of blood neurofilament light levels, a clinically relevant biomarker for axonal injury/degeneration. This study provides a proof of principle for viral gene replacement therapy targeted to Schwann cells to treat Charcot-Marie-Tooth disease type 4C and potentially other similar demyelinating inherited neuropathies.

Keywords: Charcot-Marie-Tooth 4C disease; Schwann cells; biomarkers; gene therapy; peripheral neuropathy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Charcot-Marie-Tooth Disease / genetics*
  • Charcot-Marie-Tooth Disease / metabolism
  • Charcot-Marie-Tooth Disease / therapy*
  • Disease Models, Animal*
  • Genetic Therapy / methods*
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / deficiency
  • Intracellular Signaling Peptides and Proteins / genetics*
  • Mice
  • Mice, Knockout
  • Mice, Transgenic

Substances

  • Intracellular Signaling Peptides and Proteins
  • SH3TC2 protein, human

Supplementary concepts

  • Charcot-Marie-Tooth disease, Type 4C