Mice homozygous for the Gusmps-2J allele exhibit a phenotype similar to Gusmps homozygotes including skeletal deformities, lysosomal storage disease and elevated levels of the lysosomal enzymes alpha-galactosidase and beta-hexosaminidase (Gwynn et al., 1998). Like the Gusmps heterozygote, Gusmps-2J heterozygotes have a 26-85% reduction in beta-glucuronidase activity depending on tissue type (Gwynn et al., 1998, Birkenmeier et al., 1989). Homozygotes of both alleles have beta-glucuronidase activity levels at 1% of the control level. Unlike the Gusmps homozygote, Gusmps-2J homozygotes on the C3H background live longer, are fertile and can raise litters to weaning age (Gwynn et al., 1998). In addition to a difference in the nature of the mutations between these two alleles, it is also likely that the phenotypic differences are the result of strain background. C3H/HeOuJ mice carry a different set of alleles at the Gus complex than C57BL/6J mice. Beta-glucuronidase activity in C3H/HeOuJ mice is 10-38% that of C57BL/6J mice (Gwynn et al., 1998). The Gus complex alleles determine the rate of enzyme synthesis and may modulate the expression of the beta-glucuronidase deficiency. This strain is a model for the human lysosomal storage disease, mucopolysaccharidosis type VII.
In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. This is the case for the strain above. It should be noted that the phenotype could vary from that originally described.
