Biochemical Expression of Mosaicism in Female Mice Heterozygous for the Jimpy Gene

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Abstract
Expression of the jimpy gene in heterozygous females was analyzed by measuring galactolipid synthesis in brain during early myelination. Sulfatide labeling in brains of heterozygous females at 13-14 days is decreased to 40-80% that of female littermates who do not carry the jimpy gene. The activities of ceramide galactosyl transferase and cerebroside sulfotransferase and levels of myelin basic protein were similarly depressed. Since the jimpy gene was maintained with the Tabby gene in these studies, the effect of the Tabby gene of these parameters was examined and had no effect. These biochemical findings indicate that myelination is retarded in the brains of heterozygous jimpy females during the 2nd wk of development. At 18 days and thereafter, sulfatide labeling is less reduced. The oligodendrocytes in brain may attempt to compensate, in agreement with morphological studies which show that myelin is decreased in brain during early development, but appears normal in adult animals.