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Ultrastructural distribution of PMP22 in Charcot-Marie-Tooth disease type 1A
C Haney1, G J Snipes, E M Shooter
1Department of Neurosciences, Cleveland Clinic Foundation, Ohio 44195, USA.
Abstract:
Peripheral Myelin Protein-22 (PMP22) is a membrane glycoprotein which represents up to 5% of total protein in myelin of peripheral nerves. Mutations affecting the PMP22 gene have been linked to the inherited peripheral neuropathies Charcot-Marie-Tooth disease type 1A (CMT1A; duplications and point mutations), Dejerine-Sottas syndrome (DSS; point mutations), and hereditary neuropathy with liability to pressure palsies (HNPP; deletions). In this study, we determined the ultrastructural distribution of PMP22 and other myelin proteins in normal human peripheral nervous system (PNS) nerves and in CMT1 patients with or without the CMT1A duplication on chromosome 17. Our results demonstrate that PMP22, P0 protein, and myelin basic protein are present in compact myelin of all patients examined. PMP22 was also present in the plasma membrane of Schwann cells of unmyelinated fibers and onion bulbs. Although the precise biological role of PMP22 remains to be discovered, our results support the hypothesis that this protein serves multiple functions in Schwann cells.
Insights
Peripheral Myelin Protein-22 (PMP22) is crucial for peripheral nerve myelin. This study found PMP22 in compact myelin and Schwann cells, suggesting diverse roles in nerve health and disease.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Peripheral Myelin Protein-22 (PMP22) is a key component of peripheral nerve myelin.
- PMP22 gene mutations are associated with inherited neuropathies like Charcot-Marie-Tooth disease (CMT1A), Dejerine-Sottas syndrome (DSS), and hereditary neuropathy with liability to pressure palsies (HNPP).
Purpose of the Study:
- To investigate the ultrastructural distribution of PMP22 and other myelin proteins in normal human peripheral nervous system (PNS) and in CMT1 patients.
- To correlate PMP22 distribution with different PMP22 gene mutations and associated neuropathies.
Main Methods:
- Immunoelectron microscopy was used to examine the distribution of PMP22, P0 protein, and myelin basic protein.
- Analysis was performed on normal human PNS nerves and on nerves from CMT1 patients with or without the CMT1A duplication.
Main Results:
- PMP22, P0 protein, and myelin basic protein were found in compact myelin in all examined patients.
- PMP22 was also detected in the plasma membrane of Schwann cells in unmyelinated fibers and in onion bulbs.
- These findings were consistent across patients with different PMP22 mutations.
Conclusions:
- PMP22 is present in compact myelin and Schwann cell membranes, indicating multiple functions.
- The distribution of PMP22 supports its role in both myelinated and unmyelinated peripheral nerve fibers.
- Further research is needed to fully elucidate the precise biological functions of PMP22 in Schwann cells.