Genetic polymorphism in normal human fibroblasts as analyzed by two-dimensional polyacrylamide gel electrophoresis

Two dimensional gel electrophoresis has been used to measure the degree of genetic polymorphism among the proteins of normal human fibroblasts. Autoradiographic analysis of the gel protein profiles from radioactively labeled cells allowed comparison of as many as 300 discrete polypeptides at a time. In addition, a newly developed technique for double label autoradiography was used to increase the sensitivity of the system for detection of small differences in the protein profiles of different cell lines. Only about 1.2% of the proteins of different cell lines were found to differ in their electrophoretic mobility. This corresponds to an average heterozygosity of approximately 0.6%. Previous studies of genetic polymorphism using different methods of one-dimensional electrophoretic analysis have estimated the average heterozygosity of the human population at about 6.7%. Detailed mathematical analysis shows the variation of the observed from the expected number of differences to be statistically highly significant. While the reasons for this difference are not clear, the observation of low levels of genetic polymorphism on two-dimensional gels should enhance the usefulness of this technique for detection of altered proteins in inherited disease.