Analysis of in vivo function of glycosphingolipids with glycosylation mutant mice

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In this project, we have analyzed the roles of carbohydrates in gangliosides, sialic acid-containing acidic glycosphingolipids, and their mechanisms using gene knock-out mice of glycosyltransferases responsible for the synthesis of them. The mutant mice analyzed are GM2/GD2 synthase knock-out mice lacking complex gangliosides, GD3 synthase knock-out mice lacking b-series gangliosides, double knock-out mice generated by mating the two mutants described above, and β4-galactosyltransferase 6 knock-out mice responsible for the synthesis of lactosylceramide, a precursor of the majority of gangliosides. In the null mutant mice lacking complex gangliosides, degeneration and destruction peripheral nerves and spinal cords with aging, and marked atrophy and degeneration of cerebellum were also observed. On the other hand, in the null mutant mice of GD3 synthase lacking b-series gangliosides, no apparent abnormal phenotypes were detected. However, only male mutants showed abnormal neurological function in the behavioral examination. In the double knock-out mutants generated from the two mutants described above, definite neuronal degeneration was found even in the young mice ; and refractory skin lesions appeared at faces and necks at 12 weeks after birth. Based on the peripheral nerve degeneration, lowered function of pain sensation might induce frequent repeated scratching toward the wound site, and might trigger the skin lesions. Although we have tried to identify genes which show big differences in the expression levels between the null mutant and wild type mice using a DNA array or cDNA subtraction, no definitely important genes have not yet identified. With RNA extraction from specific sites of tissues or expression analysis with minimal levels of RNA, we will identify the genes involved in the degeneration and regeneration, and clarify the original molecular function of those gene products in the near future.