Molecular basis of feline beta-glucuronidase deficiency: An animal model of mucopolysaccharidosis VII

A family of domestic cats was found that exhibited clinical and biochemical abnormalities consistent with mucopolysaccharidosis VII, an autosomal rece ssive lysosomal storage disorder caused by beta-glucuronidase deficiency. b eta-Glucuronidase activity was undetectable in affected cat fibroblasts and restored by retroviral gene transfer of rat beta-glucuronidase cDNA. beta- Glucuronidase mRNA was normal in affected cat testis by Northern blot analy sis. Normal feline beta-glucuronidase cDNA was cloned and characterized, an d amplified from affected cat fibroblasts by reverse transcription coupled polymerase chain reaction. There was a G-to-A transition in the affected ca t cDNA that predicted an E351K substitution, destroyed a BssSI site, and el iminated GUSB enzymatic activity in expression studies. Multiple species co mparison and the crystal structure of human beta-glucuronidase indicated th at E351 is a highly conserved residue most likely essential in maintenance of the enzyme's conformation. BssSI digestion of polymerase chain reaction products amplified from genomic DNA indicated that affected cats were homoz ygous and cats with half-normal beta-glucuronidase activity were heterozygo us for the missense mutation. Carriers identified in this manner produced a ffected kittens in prospective breedings, and a feline MPS VII breeding col ony has been established. (C) 1999 Academic Press.