Lymphocyte proteins in Huntington's disease: Quantitative analysis by use of two-dimensional electrophoresis and computerized densitometry

Abstract

We used quantitative two-dimensional electrophoresis to study lymphocyte proteins in Huntington's disease. Three hundred and six polypeptides from 14C-labeled, phytohemagglutinin-stimulated lymphocytes were measured for variation in relative spot density and 186 for variation in spot position by use of a computer program requiring operator interaction. Each polypeptide was measured in a total of 30 electrophoretograms from 28 individuals, including 13 with Huntington's disease, 2 at risk for it, and 13 controls. The study included two sets of identical twins and, as neurological controls, individuals with neurofibromatosis, Alzheimer's disease, or Shy-Drager syndrome. Seven protein polymorphisms were identified among the 186 most dense polypeptides of each gel, corresponding to a minimum average heterozygosity of 1.4%. Stringent criteria were used to define polymorphic proteins, including observation of at least one individual with each of two homozygous phenotypes and one with the heterozygous phenotype, demonstration of the expected gene dosage relationship by quantitative densitometry, consistency with genetic relationships, and reproducibility. One polymorphic protein showed three electrophoretically variant alleles. Our identification of seven polymorphisms among the 186 proteins measured on a single electrophoretogram illustrates the potential of this technique for performing linkage analysis in diseases of genetic origin. However, we observed no quantitative or positional protein variations that were characteristic of (i.e., specific for) Huntington's disease.