Sequence analysis of the human tyrosinase promoter from a patient with tyrosinase-negative oculocutaneous albinism.

We examined the tyrosinase gene from a patient with tyrosinase-negative oculocutaneous albinism (OCA). First we studied the protein coding region, exon/intron junctions, and the proximal promoter region (positions -300 to +1) of her tyrosinase gene by direct sequencing. Although the results showed that she was heterozygote for the R77Q mutation, we could find no other mutation. To find a second mutation and compare the sequence in the 5'-flanking region of her tyrosinase gene between two OCA alleles, we amplified a 2422-bp stretch (positions -2065 to +357, including R77Q mutation site) by PCR, and cloned it into a plasmid vector. As a result, we discovered a difference between two OCA alleles in the GA repeat region. Therefore, we expect that the polymorphism in the GA repeat region of the tyrosinase gene will be used as a flanking marker of the OCA allele.