Modeling of the Pathogenic Effect of Copper Transporter Mutations That Cause Menkes and Wilson Diseases, Motor Neuropathy, and Susceptibility to Alzheimer's Disease.

Copper is an essential biometal, and several inherited diseases are directly associated with a disruption to normal copper homeostasis. The best characterized are the copper deficiency and toxicity disorders Menkes and Wilson diseases caused by mutations in the p-type Cu-ATPase genes and , respectively. Missense mutations in the C-terminal portion of have also been shown to cause distal motor neuropathy, whereas polymorphisms in are associated with increased risk of Alzheimer's disease. We have generated a single, model for studying multiple pathogenic mutations in ATP7 proteins using , which has a single orthologue of ATP7A and ATP7B. Four pathogenic mutations and two mutations were introduced into a genomic rescue construct containing an in-frame C-terminal GFP tag. Analysis of the wild type transgene confirmed that ATP7 is expressed at the basolateral membrane of larval midgut copper cells and that the transgene can rescue a normally early lethal deletion allele to adulthood. Analysis of the transgenes containing pathogenic mutations showed that the function of ATP7 was affected, to varying degrees, by all six of the mutations investigated in this study. Of particular interest, the ATP7B Alzheimer's disease susceptibility allele was found, for the first time, to be a loss of function allele. This system allows us to assess the severity of individual / mutations in an invariant genetic background and has the potential to be used to screen for therapeutic compounds able to restore function to faulty copper transport proteins.