In southern Africa, brown oculocutaneous albinism (BOCA) maps to the OCA2 locus on chromosome 15q: P-gene mutations identified

In southern Africa, brown oculocutaneous albinism (BOCA) is a distinct pigm entation phenotype. In at least two cases, it has occurred in the same fami lies as tyrosinase-positive oculocutaneous albinism (OCA2), suggesting that it may be allelic, despite the fact that this phenotype was attributed to mutations in the TYRP1 gene in an American individual of mixed ancestry. Li nkage analysis in five families mapped the BOCA locus to the same region as the OCA2 locus (maximum LOD 3.07; theta = 0 using a six-marker haplotype). Mutation analysis of the human homologue of the mouse pink-eyed dilution g ene (P), in 10 unrelated individuals with BOCA revealed that 9 had one copy of the 2.7-kb deletion. No other mutations were identified. Additional hap lotype studies, based on closely linked markers (telomere to centromere: D1 5S1048, D15S1019, D15S1533, P-gene 2.7-kb deletion, D15S219, and D15S156) r evealed several BOCA-associated P haplotypes. These could be divided into t wo core haplotypes, suggesting that a limited number of P-gene mutations gi ve rise to this phenotype.