Complementation studies in human and feline Niemann-Pick type C disease.

Complementation studies were performed to determine if the gene responsible for the major form of human Niemann-Pick type C disease (NPC) and a feline model of NPC are orthologous. Cell fusions between human NPC and feline NPC fibroblasts were conducted to assess whether the multinucleated heterokaryons that were formed showed a reversal of the NPC phenotype. Cultured fibroblasts from NPC-affected humans and NPC-affected cats were hybridized and then analyzed for complementation by challenging the cells with low-density lipoprotein (LDL) and subsequently staining with the fluorescent antibiotic filipin to visualize any abnormal accumulation of unesterified cholesterol. All of the multinucleated cells formed from these fusions retained the NPC staining phenotype, indicating an absence of complementation and suggesting that the underlying defect in the major form of human NPC and this feline model of NPC involve orthologous genes.