A deficiency of peripheral myelin protein-22 (PMP22) – a protein expressed by the cells that “wrap” myelin around nerve axons to speed signaling – causes an inherited neuropathy (HNPP) that results in focal sensory loss and limb paralysis. The biological role of PMP22 is unclear.
Using a mouse model of HNPP, Jun Li, M.D., Ph.D., and colleagues previously demonstrated that PMP22 deficiency impaired nerve electrical signaling in the absence of demyelination (the presumed cause for conduction problems in HNPP). Now, they have found that PMP22 deficiency disrupts the assembly of multiple types of myelin junction protein complexes, which are required to form a “seal” that enables effective nerve conduction. They showed that loss of myelin junctions increased myelin permeability and impaired the propagation of electrical signals.
The findings, reported in the February issue of the Annals of Neurology, reveal a role for PMP22 in myelin junctions. The study also demonstrates that disruption of myelin junctions is functionally comparable to demyelination in its impact on nerve cell signaling.
This research was supported by grants from the National Institutes of Health (NS066927, NS064278) and by funding from the Prinzmetal Family and the Swiss National Science Foundation.
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