Pathogenesis and Treatment of beta-Galactosidase-Deficient Knockout Mice

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We succeeded in producing a mouse model of human G_<M1>-gangliosidosis by disruption of the murin beta-galactosidase gene, in order to analyze its pathogenesis and to try therapeutic approaches. Clinically the mutant mouse developed a progressive neurological disease 4 months after birth, manifesting itself as spastic diplegia. They died of severe nervous system dysfunction and extreme emaciation at 7-11 months of age. Neuronal cytoplasmic swelling due to storage of undigested substrates was observed in every area of the central nervous system, and the storage material appeared as membranous cytoplasmic bodies electron microscopically. This morphological change progerssed rapidly between 4 and 8 weeks of age. beta-Galactosidase activity was almost compeltely deficient in all tissues and body fluids examined.Biochemical analysis revealed a marked storage of ganglioside G_<M1> and its asialo derivative G_<A1>D in the central nervous system and some solid tissues, such as liver and spleen. G_<A1> storage was more remarkable as compared to that in human patients. These results indicated that this model animal is an authentic murine counterpart of human G_<M1>-gangliosidosis. However, there was no bone dysplasia or keratan sulfaturia in these disease mice. Urinary oligosaccharides showed an abnormal pattern on thin-layr chromatography which was similar to that in infantile G_<M1>-gangliosidosis. As an experimental trial, an adenovirus-mediated intravenous injection of beta-galactosidase cDNA was preformed into the mutant newborn mouse. The beta-galactosidase activity was expressed in the central nervous system 2 weeks after injection at the 10% normal lavel. At this stage, storage of G_<M1> and G_<A1> was significantly reduced as compared to animals without treatment. We concluded that the gene introduced in the vascular system has reached the central nervous system through the undeveloped blood-brain barrier in the neonatal period.