Two spontaneous mutant beige rats, with phenotypes resembling human Chediak- 
Higashi syndrome (CHS), were found independently in two inbred strains. Both 
beige mutations were identified to be recessive alleles in the Lyst locus on rat 
chromosome 17 and the alleles were denoted Lyst(bg) and Lyst(bg-Kyo). As it is 
almost impossible to discriminate these mutations phenotypically, we developed 
an allele-specific genotyping method for the Lyst gene. The nested PCR 
amplification was followed by restriction fragment length polymorphism (RFLP) 
analysis. By this method, we could discriminate the mutant Lyst(bg), 
Lyst(bg-Kyo) alleles, and the normal Lyst allele, easily and accurately.