Detection of the nt230[del4] MDR1 mutation in dogs by a fluorogenic 5′ nuclease TaqMan allelic discrimination method

For detection of the nt230[del4] MDR1 mutation, a 4-bp deletion in the canine MDR1 (ABCB1) gene, a TaqMan allelic discrimination assay was designed that allows for MDR1 genotyping without post-PCR processing. Directly after completion of the PCR amplification, the MDR1 genotype can be assigned based on selective fluorescence measurement. For primer selection the locus of a potential 265A > G single nucleotide polymorphism was omitted; this locus is covered by the oligonucleotide PCR primers from most of the hitherto established MDR1 genotyping methods. Dogs homozygous for the nt230[del4] MDR1 mutation show highly increased susceptibility to many drugs commonly used in veterinary medicine including ivermectin. As more than 10 dog breeds are predisposed to this mutation, reliable genotyping methods are necessary to identify affected dogs before drug treatment. This study provides a new allelic discrimination method that detects the MDR1 mutation with high specificity and reliability and is useful for routine diagnostics.