Neuroinflammation in the pathogenesis of axonal Charcot-Marie-Tooth disease caused by lack of GDAP1

Abstract

Mutations in the GDAP1 mitochondrial outer membrane gene cause Charcot-Marie-Tooth (CMT) neuropathy. Reduction or absence of GDAP1 has been associated with abnormal changes in the mitochondrial morphology and dynamics, oxidative stress and changes in calcium homeostasis. Neuroinflammation has been described in rodent models of genetic demyelinating CMT neuropathies but not in CMT primarily associated with axonopathy. Inflammatory processes have also been related to mitochondrial changes and oxidative stress in central neurodegenerative disorders. Here we investigated the presence of neuroinflammation in the axonal neuropathy of the Gdap1^-/- mice. We showed by transcriptome profile of spinal cord and the in vivo detection of activated phagocytes that the absence of GDAP1 is associated with upregulation of inflammatory pathways. We observed reactive gliosis in spinal cord with increase of the astroglia markers GFAP and S100B, and the microglia marker IBA1. Additionally, we found significant increase of inflammatory mediators such as TNF-α and pERK, and C1qa and C1qb proteins of the complement system. Importantly, we observed an increased expression of CD206 and CD86 as M2 and M1 microglia and macrophage response markers, respectively, in Gdap1^-/- mice. These inflammatory changes were also associated with abnormal molecular changes in synapses. In summary, we demonstrate that inflammation in spinal cord and sciatic nerve, but not in brain and cerebellum, is part of the pathophysiology of axonal GDAP1-related CMT.

Keywords: Axonopathy; Charcot-Marie-tooth disease; GDAP1; Gdap1 knockout mouse; Neuroinflammation.