Charcot-Marie-Tooth disease (CMT) is a group of disorders and the most common inherited peripheral
neuropathy with a prevalence of 1:2500. Approximately 1,000 small mutations (missense, nonsense, small
deletion or insertion, splice alterations) in more than 40 genes are responsible for CMT. CMT severely
impacts
the
is
orthopedic
quality of life for patients and
no effective prevention or cure for CMT, and patient care is limited to physical and occupational therapies,
devices, and pain relief, which is often suboptimal.
accounts for significant lifelong disability and important economic loss. There
CMT type 1 is a demyelinating peripheral
neuropathy characterized by reduced motor nerve conduction velocities (less than 38 m/s) and segmental
demyelination and remyelination with onion bulb formations on nerve biopsy. Despite the different subtypes of
CMT associated with distinct genetic causes and pathogenetic mechanisms, all forms of CMT1 eventually
converge on the loss of myelinated nerve fibers. Thus, a common approach based on enhancing myelination in
diseased nerves without exacerbating myelin damages must be identified to provide widely effective therapy for
the array of CMT neuropathies.
We previously showed that enhancing axonal NRG1tIII signaling increases fatty acid levels in myelin,
improves myelination and nerve function in mouse models for inherited demyelinating neuropathy, through an
alternative EGR2-independent pathway. Notably, we found that PMP2, a fatty acid-binding protein is uniquely
up-regulated downstream NRG1tIII overexpression in Schwann cells. Our central hypothesis of this proposal is
that overexpression of the fatty acid-binding protein PMP2 is a downstream promyelinating mediator of NRG1tIII-
mediated hypermyelination and that sustained overexpression of PMP2 is sufficient to improve myelin formation,
without exacerbating myelin damages. We have now compelling preliminary evidence that PMP2
overexpression in Schwann cells enhances the uptake of fatty acid, increases ATP production, and is beneficial
to Schwann cell myelination and remyelination. Thus, we propose to determine if PMP2 overexpression is a
suitable strategy to improve myelination defects in inherited peripheral demyelinating neuropathy (P0S63del),
which of PMP2 functions are beneficial to improve myelin formation, and how Pmp2 expression is being
regulated. The new mechanistic insights on PMP2 overexpression enhancing myelination we will gain from this
work are in line with NINDS objective seeking fundamental knowledge about the nervous system that may
facilitate the development of future interventions to reduce the disease burden in patients with peripheral
neuropathies.