Myelin Basic Protein Deposition in the Optic and Sciatic Nerves of Dysmyelinating Mutants Quaking, Jimpy, Trembler, MLD, and Shiverer During Development

Abstract

An ontogenetic survey of the basic protein of myelin, common to both central and peripheral nervous systems, was carried out on normal C57B1 and five dysmyelinating mutant mice. Myelin basic protein (MBP) was quantified by radioimmunoassay in the optic and sciatic nerves of mice from birth to adult stages, giving special attention to the premyelinating and early myeli-nation periods. In the optic nerves of normal mice, MBP was already detectable at birth but the active period of myelin deposition was shown to occur after day 10 postnatal. The timing and rate of accumulation of MBP were normal in Trembler. In contrast, they were abnormal in the other mutants. In the quaking mouse, the active period of MBP deposition was delayed, and its final concentration represented no more than 12% of normal in the adult. No active period of MBP deposition was observed in the other mutants. In the jimpy mouse, a slow accumulation of MBP resulted in a final concentration reaching 2% of the normal value at 25 days. In mid and shiverer mice, the MBP was hardly detectable. In the sciatic nerves of normal mice, the active period of MBP deposition occurred between days 3 and 12 postnatal. No substantial changes occurred in the period of 2 months-2 years. Deposition of MBP was normal in jimpy. In quaking, it was not only delayed but also reduced, leading to a concentration as low as 40% of normal adult. In mid and shiverer PNS, MBP concentrations were very low but noticeably higher than in the optic nerve. In the sciatic nerve of Trembler a myelination-demyelination process was strongly suggested by MBP determination. After a delayed but active period of deposition from days 5–11 postnatal, the MBP content was found to decline within a few days and remained almost undetectable until old age.