The quaking mouse: regional variations in the content and protein composition of myelin isolated from the central nervous system

Myelin was isolated from six regions of the central nervous system of quaking and littermate control mice. The yield of myelin from the mutant animals ranged from 2% of the control level in the most rostral parts of the central nervous system to 16% in the spinal cord, with an intermediate value (10%) for the optic nerves; these results are in close agreement with the data of others obtained by quantitative electron microscopy. Electrophoretic analyses of myelin from the telencephalon, diencephalon, brain stem and spinal cord revealed a marked deficit of proteolipid and small basic proteins in all fractions from quaking mice; however, neither of these proteins exhibited clear rostro-caudal trends with respect to the ratio of protein contents between quaking and control mice.An hypothesis is proposed to account for the regional variations in the mutant's myelin deficit; it is suggested that the quaking mutation induces an arrest in myelinogenesis through a mechanism which is common to both oligodendroglial and Schwann cells.