Synthesis of myelin proteins in a leucodystrophy

Abstract

The leuoodystrophy “jimpy”, a recessive mutation in the mouse, is characterised by a defective myelin formation. At a previous meeting we showed that the activity of several enzymes involved in the synthesis of myelin lipids is diminished, resulting in a decreased amount of these lipids in “Jimpy” brains. Since the myelin basic protein, an important component of the myelin membrane, was also found in a low amount, the synthesis of these protein was studied. A quantitative assay was worked out based on the observation that digestion with pepsin under controlled conditions releases from the myelin basic proteins a specific peptide that can be isolated after acrylamide gel electrophoresis. Using H3-Prolin we could study the synthesis of this peptide and thus of basic myelin protein. The rate of synthesis was found normal. in Jimpy mice. In “chase” ezperiaents, however, the degradation of Jimpy basic protein was greatly accelerated. In the jimpy leucodystrophy the vet amount of myelin lipida is regulated therefore by the rate of synthesis, that of the basic proteins, however, by the rate of degradation.