THE GENE FOR LYSOSOMAL PROTEIN CD63 IS NORMAL IN PATIENTS WITH HERMANSKY-PUDLAK-SYNDROME

Hermansky-Pudlak syndrome (HPS) is one of the few genetic disorders as sociated with severe pulmonary fibrosis. Fifty percent of affected pat ients die as a result of respiratory insufficiency. Fibrosis is though t to be caused by the accumulation of ceroid, an insoluble fluorescent lipoprotein, both extracellularly and in the lysosomes of alveolar ma crophages. In addition to pulmonary fibrosis, HPS is characterized by oculocutaneous albinism and a reduction in the number of platelet dens e bodies. CD63 is a protein that was described originally in platelet lysosomes, It localizes to the membranes of melanosomes and platelet d ense bodies. CD63 is decreased dramatically in the lysosomes and dense bodies of patients with HPS. We theorized that CD63, a membrane prote in common to lysosomes, melanosomes, and platelet dense bodies, may pl ay a role in HPS. We sought to characterize the gene coding for this p rotein in HPS lymphoid cell lines. The coding region for CD63 was sequ enced in control and HPS cell lines. Messenger RNA from HPS and normal cell Lines was examined by Northern analysis. Genomic DNA from the sa me cell lines was examined by Southern analysis and polymerase chain r eaction (PCR). CD63 protein in lymphoid cell lines and peripheral bloo d monocytes was compared by Western analysis. We found no mutations in the coding region of CD63 in an HPS cell line. We also found no dimin ution in the quantity of CD63 RNA by Northern analysis and no gross de fects in the structural gene by PCR and Southern analysis, suggesting that the CD63 structural gene, promoter, and untranslated regions were normal. Western analysis showed that the 43-kDa protein was present i n control and HPS lymphoid cell lines and peripheral blood monocytes i n equivalent amounts. Although CD63 is an attractive candidate for the primary defect of HPS, the disease is probably not caused by a mutati on in the CD63 gene.