A 4-bp deletion promoter variant (rs984225803) is associated with mild OCA4 among Japanese patients.

Oculocutaneous albinism (OCA) type 4 is one of the most common types of albinism among Japanese population. In some patients who were clinically diagnosed with OCA, we have found a heterozygous pathological mutation in the coding region of SLC45A2, the gene responsible for OCA4, not leading to a DNA-based diagnosis. In this study, we evaluated pathological variants in the promoter region of SLC45A2 in these patients. The results indicated that the majority of the patients had a 4-bp deletion in the said region (c.-492_489delAATG; GenBank accession number: NM_016180; rs984225803) in the contralateral allele. These patients displayed a mild phenotype, especially regarding eye manifestations. The results of the luciferase reporter assay and electrophoretic mobility shift assay supported the pathological role of the variant. In addition, four of 220 alleles in Japanese normal control subjects also showed the deletion variant, indicating that this variant could possibly be a skin color-associated variant.