Comparison of polymerase chain reaction-restriction fragment length polymorphism assay and enzyme assay for diagnosis of GM1- gangliosidosis in Shiba dogs

Abstract

In the present study, diagnostic methods for canine GM1- gangliosidosis were examined by comparing a DNA mutation assay with an enzyme assay. Sixty-two Shiba dogs of a pedigree with GM1-gangliosidosis were differentiated into 3 genotypes, i.e., normal, heterozygous, and homozygous affected dogs, using a DNA mutation assay, which consists of polymerase chain reaction amplification and the determination of restriction fragment length polymorphisms. The β-galactosidase activity in leukocytes, umbilical cords, and plasma was measured using 4-methylumbelliferyl β-D-galactoside and p-nitrophenyl β-D-galactoside as artificial substrates and compared among the 3 genotypes. The results showed that it was possible to identify homozygous dogs with the enzyme assay using leukocytes and umbilical cords. When using leukocytes, heterozygous carriers could be differentiated from normal dogs in many cases. However, the use of the DNA mutation assay is essential for a complete determination of heterozygous carriers because of the overlap in the distribution of enzyme activity between these 2 groups. When umbilical cords were used, heterozygous carriers could not be differentiated from normal dogs because of no significant difference in enzyme activity between these 2 groups. The β-galactosidase activity in plasma was not applicable to the diagnosis and genotyping of GM1-gangliosidosis in Shiba dogs.