A yeast system for analysis of intracellular trafficking defects in niemann-pick C disease

The regulated trafficking of lipids between cellular compartments is an essential but poorly understood process. The importance of this regulation is highlighted in Niemann-Pick C (NPC) disease, a lethal neurodegenerative disorder characterized by defective intracellular trafficking of lipids and other metabolites. Mutation of the NPC1 gene is responsible for most cases of NPC disease. Our approach to understanding NPC1 is to investigate the single yeast NPC1-related gene, NCR1. Yeast has pathways of intracellular transport, lipid synthesis and regulation similar to those in human cells. We have shown that NCR1 is required for efficient intracellular trafficking while its over-expression is toxic. Ordered arrays of yeast strains, each containing a different gene deletion, will be robotically screened to identify all yeast genes that either enhance or alleviate the toxicity caused by excess NCR1 protein. Biochemical and molecular genetic analyses of these genetic interactions will determine how the normal NCR1 protein functions within the cell. The availability of genomic and protein data through online databases, the ease of genetic manipulation, and the rapid growth rate, all facilitate analyses in yeast. The availability of the complete sequence of both the yeast and human genome allows for a rapid transition from yeast to direct tests of the functions of the mammalian versions of any genes identified in our study. This research will help determine the basis for NPC disease and is therefore of direct relevance to hundreds of people with the disease and their families. The findings, by providing a better understanding of lipid regulation, will also have broader relevance for many common human disorders, such as hypercholesterolemia, atherosclerosis and coronary heart disease.