BACKGROUND: Oculocutaneous albinism (OCA) is a heterogeneous congenital 
disorder. Tyrosinase is a key enzyme in melanin biosynthesis, and tyrosinase 
gene mutations cause the OCA1 subtype.
OBJECTIVE: This study was intended evaluate the frequency and details of 
tyrosinase gene mutations in Japanese OCA patients.
PATIENTS AND METHODS: We examined nine non-consanguineous OCA families, 
sequenced the tyrosinase gene of the patients and also confirmed a splicing site 
mutation using exon trapping system.
RESULTS: Tyrosinase gene mutations were identified in five out of nine OCA 
families (55%). IVS2-10deltt-7t-a was present in 3 out of 18 alleles in three 
families (16%), P310insC was present in three alleles in three families (16%) 
and R278X was found in three alleles (16%), including those in one heterozygous 
and one compound homozygous patient. G97V (290 G-T) was found in 1 out of 18 
alleles, and we could not find G97V in the mutation database. We have added this 
mutation as 9th mutation of Japanese OCA1 patients. In 8 of 18 alleles, four 
families, no tyrosinase mutations were identified. They were presumed not to be 
OCA1, but other subtypes of OCA. Exon trapping system demonstrated 
IVS2-10deltt-7t-a mutation generated the abnormal splicing site, and inserted 
the codon 4 bases in mRNA level resulting in premature termination codon 
downstream.
CONCLUSION: This study provided new information about OCA1 mutations, and 
highlights the requirement of broader detailed search to make precise diagnosis 
of OCA.