The distribution of myelin basic protein in subcellular fractions of developing Jimpy mouse brain.

Abstract

Abstract— The amount of myelin basic protein in jimpy mutants and unaffected littermates was measured by radioimmunoassay during the period of most active myelination (11‐21 days). This protein was examined in whole brain homogenates and in four subcellular fractions (nuclear, 900 g pellet; heavy membrane, 11,500 g pellet; microsomal, 100,000 g pellet; and cytosol, 100,000g supernatant solution). At all ages examined, the mutants, which have very little myelin in the CNS, had only about 2% the amount of basic protein found in controls. As expected, the amount of myelin basic protein increased 4‐fold in the control animals during the developmental period studied. This was not the case in the jimpy mutants, where little increase in the whole brain basic protein was observed. In the jimpy mutants, all of the fractions had significantly less basic protein than control fractions, except the cytosol, where the amounts of basic protein were similar in controls and mutants. These results are discussed with respect to possible mechanisms of myelination and the site of the genetic lesion.