[Mutations and polymorphisms of the P gene associated with oculocutaneous albinism type II]

Oculocutaneous albinism typeII(OCA2), the most common type of albinism, is an autosomal recessive disorder. It is caused by mutations in the P gene, which is located on chromosome 15q11.1-q12 and divided into 24 exons and 23 introns. P gene codes for 838-amino-acid integral membrane protein with 12 putative transmembrane domains, but the exact function is not clear yet. There are at least 60 pathologic mutations and 43 non-pathologic polymorphisms have been found. Pathologic mutations include missense mutations, nonsense mutations, frameshift mutations and splice-sit mutations. But unlike TYR gene, most of P gene mutations are located on the C-terminal and don' t cluster in defined regions. It is difficult to define the pathologic mutations since many non-pathologic polymorphisms also lie in exons. Some non-pathologic missense mutations may be associated with phenotypic variation in normally pigmented individuals and need to further study.