QUAKING MOUSE: ISOLATION AND CHARACTERIZATION OF MYELIN PROTEIN

Abstract

A new technique, involving final purification on a continuous CsCl gradient, was utilized for the isolation of cerebral myelin from adult (4‐ to 6‐month‐old) quaking mice, littermate controls and young (10‐day‐old) normal mice. The yield of myelin from either adult quaking or normal young mice was 5‐10 per cent of that from adult controls. After deli‐pidation, myelin proteins were separated by polyacrylamide gel electrophoresis in buffers containing sodium dodecylsulphate. Two gel systems were utilized: (1) a high‐resolution discontinuous electrophoresis system; and (2) a continuous system utilizing gels cross linked with ethylenediacrylate (EDA). The gels from the discontinuous system were stained with Fast Green and quantified by densitometry. The base lability of the EDA‐linked gels permitted direct chemical determination of protein in specific bands. Myelin from brains of normal adult mice contained, as major components, one proteo‐lipid and two basic proteins. There were also a number of high‐molecular‐weight proteins which represented a significant portion of the total. Myelin from quaking mice had qualitatively a similar distribution of proteins but the high‐molecular‐weight fraction comprised a much greater percentage of the total protein. The ratio of basic to proteolipid protein in preparations from quaking mice was considerably higher than that in the myelin from control mice. The distribution pattern of the myelin proteins from 10‐day‐old mice was quantitatively similar to that of quaking mice. Altogether the evidence supports the hypothesis that the quaking mutant provides a model of an immature nervous system with respect to myelination.