Quantitative two-dimensional protein electrophoresis for studies of inborn errors of metabolism

High-resolution electrophoretic methods and sensitive protein-detection techniques permit new approaches to understanding and diagnosis of the inborn errors of metabolism. These approaches encompass: the search for protein alterations that represent primary mutations effects; observation of alterations in protein patterns due to secondary effects, as might occur in major metabolic pathway abnormalities; and identification of protein polymorphisms that are genetically linked to an inborn metabolic disease. With the aid of computer analysis of the electrophoretograms, all three approaches are being developed. Protein density and position are evaluated with an interactive computer program that requires that gel polypeptides be indexed by the investigator. Proteins on the gels are made visible with an inexpensive, rapid silver stain, which can be used quantitatively. The Lesch-Nyhan syndrome, one of a few neuropsychiatric diseases for which the molecular defect is known, was chosen for study with these techniques. Four hundred proteins were analyzed for positional or quantitative variation. Eleven significant (2p less than 0.01) quantitative differences were found in autoradiograms from gels of phytohemagglutinin-stimulated lymphocytes. Specific patterns of polypeptide variation are now being sought in an expanded clinical study primarily focusing on Huntington's disease. Large studies are required to establish the specificity of observed alterations. As the number and variety of analyses increase, a correlative catalog of molecular variation and polymorphism will be generated.