The Journal of Neuroscience, July 9, 2008, 28(28):7068-7073; doi:10.1523/JNEUROSCI.0771-08.2008
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Brief Communications
P0 Protein Is Required for and Can Induce Formation of Schmidt-Lantermann Incisures in Myelin Internodes
Xinghua Yin,1
Grahame J. Kidd,1
Klaus-Amin Nave,2 and
Bruce D. Trapp1
1Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, and 2Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
Correspondence should be addressed to Dr. Bruce D. Trapp, Department of Neurosciences, NC30, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195. Email: trappb{at}ccf.org
Axons in the PNS and CNS are ensheathed by multiple layers of tightly compacted myelin membranes. A series of cytoplasmic channels connect outer and inner margins of PNS, but not CNS, myelin internodes. Membranes of these Schmidt-Lantermann (S-L) incisures contain the myelin-associated glycoprotein (MAG) but not P0 or proteolipid protein (PLP), the structural proteins of compact PNS (P0) and CNS (PLP) myelin. We show here that incisures are present in MAG-null and absent from P0-null PNS internodes. To test the possibility that P0 regulates incisure formation, we replaced PLP with P0 in CNS myelin. S-L incisures formed in P0-CNS myelin internodes. Furthermore, axoplasm ensheathed by 65% of the CNS incisures examined by electron microscopy had focal accumulations of organelles, indicating that these CNS incisures disrupt axonal transport. These data support the hypotheses that P0 protein is required for and can induce S-L incisures and that P0-induced CNS incisures can be detrimental to axonal function.
Key words: myelin; P0 protein; proteolipid protein; myelin-associated glycoprotein; axon; axonal transport
Received Feb. 20, 2008;
revised May 22, 2008;
accepted May 27, 2008.
Correspondence should be addressed to Dr. Bruce D. Trapp, Department of Neurosciences, NC30, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195. Email: trappb{at}ccf.org
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