A mutant allele common to the type I adenine phosphoribosyltransferase deficiency in Japanese subjects.

Adenine phosphoribosyltransferase (APRT) deficiency is a genetic disorder which causes 2,8-dihydroxy-adenine urolithiasis. The estimated incidence of heterozygosity in Caucasian and Japanese populations is 1%. Mutant alleles responsible for the disease have been classified as APRTQ0 (type I) and APRT (type II). In our previous study, we demonstrated in APRTJ a single common base change which accounts for 70% of the Japanese mutants. The present report describes the analysis of an APRTQ0 mutation in Japanese subjects. Two nucleotide substitutions common to all seven affected alleles from four unrelated subjects (three homozygotes and a heterozygote) were identified: G----A at nucleotide position 1453 and C----T at 1456. The G----A altered the amino acid Trp98 to a stop codon. The C----T did not alter Ala99. These point mutations were demonstrated by sequence analysis of polymerase chain reaction (PCR)-amplified genomic DNA and cDNA. The G----A change at 1453 results in the elimination of a PflMI site in the APRT gene. PflMI digests, which were used to confirm the G----A transition, can be useful in screening for this specific mutation.