PROTEIN AND GLYCOPROTEIN COMPOSITION OF MYELIN AND MYELIN SUBFRACTIONS FROM BRAINS OF ‘QUAKING’ MICE

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Abstract
Abstract— Quaking mutants in mice are known to be affected by an arrest of myelinogenesis and to have a purified myelin which is more dense than that of controls. Their myelin has been shown to demonstrate a striking decrease in proteolipid protein, a lesser decrease in the small myelin basic protein and changes in glycoproteins comprising reduction in the major peak and shift of this peak towards a higher apparent molecular weight. The possibility that these findings might reflect merely contamination of myelin with other membranes was tested by subfractionation. Light myelin (floats on 0.62 m‐sucrose) is generally accepted as more compact and mature than the heavier subfraction (floating on 0.85 m‐sucrose). The changes previously found were present in both subfractions and even more marked in the light myelin. These results indicate that the anomalies of myelin proteins and glycoproteins were not caused by contaminants and are present in compact myelin as well as in membranes which are transitional between the glial plasma membrane and the myelin sheath. Therefore, we suggest that the Quaking mutation results in dysmyelination rather than hypomyelination.