Murine mucopolysaccharidosis type VII is a heritable disease caused by a spontaneous mutation, gusmps, closely linked to the β-glucuronidase structural gene on chromosome 5. Mice homozygous for the mutation have a >200-fold decrease in β-glucuronidase mRNA levels and virtually no enzyme activity detectable by a sensitive fluorometric assay. Approximately 20 kb of genomic DNA containing the β-glucuronidase gene Gus and >2 kb of 5′ and 3′ flanking sequences were cloned from both a gusmps/gusmps mouse and a +/+ mouse of the progenitor strain. Restriction enzyme digests containing DNA fragments 20-400 bp in length were generated from each of the two Gus alleles and then compared by using nondenaturing polyacrylamide DNA-sequencing gels. This method rapidly identified a large number of restriction sites and was sensitive enough to detect a restriction fragment length variation resulting from a 1-bp deletion in the gusmps allele. DNA-sequence analysis of the mutant genomic fragment showed that the 1-bp deletion created a frameshift mutation within exon 10. Insertion of the deleted nucleotide by oligonucleotide site-directed mutagenesis restored function to the corrected mutant gene when transfected into gusmps/gusmps fibroblasts. We concluded that the frameshift mutation, which introduces a premature stop codon at codon 497 in exon 10, accounts for the molecular, biochemical, and pathological abnormalities associated with the gusmps phenotype.
|Number of pages
|Proceedings of the National Academy of Sciences of the United States of America
|Published - Jul 15 1993
- Animal models
- Restrictton fragment length variation detection
- Translation termination
- mRNA metabolism