Myelination in the jimpy mouse in the absence of proteolipid protein.

A point mutation in the gene for proteolipid protein (PLP) has been suggested to account for the dysmyelination seen in the jimpy mouse mutant. Despite the absence of PLP, the major integral membrane protein of central nervous system (CNS) myelin, this study shows that there are many scattered myelinated fibers present in the spinal cord of this murine mutant which are immunocytochemically positive for myelin basic protein (MBP), yet negative for PLP. This lack of PLP results in an abnormal compaction of the extracellular leaflets of the myelin sheath and the formation of an abnormal intraperiod line. These results are similar to those seen in another X-linked myelin mutant, the myelin-deficient rat (Duncan et al.: Proc. Natl. Acad. Sci. U.S.A., 84:6287-6291, 1987), and show that a multilamellar membrane can be formed in the absence of its major integral membrane protein.