Detection of Mutated Erythrocytes in Man
Two assay systems are being developed to measure the level of in vivo somatic mutations in human cells. Both are based on immunologic recognition and fluorescence-activated cell sorter enumeration of cells carrying variant proteins. The first assay is based on the detection of erythrocytes containing the single amino acid-substituted hemoglobins S or C. Frequencies of anti-hemoglobin S- and C-labeled red cells in the blood of normal hemoglobin A individuals were determined. In five samples, the S-frequencies ranged from 1.1 x 10-8 to 1.1 x 10-7. C-frequencies from 6.7 x 10-8 to 2.6 x 10-7 were observed in three samples. Methods to test the genetic validity of these results and to extend the measurements to additional point- and frameshift-mutant hemoglobins through the use of monoclonal antibodies are discussed. The second assay seeks to detect variant red cells arising as a result of “gene expression loss” and point mutations in the genes for the membrane-associated protein glycophorin A. Monoclonal antibodies, specific for the M and N allelic forms of the protein, have been produced and can be used to screen blood samples from MN heterozygotes for variant red cells which fail to present one of the glycophorin A forms. These antibodies may also be capable of detecting red cells in homozygotes expressing single amino acid-substituted glycophorin A.
KeywordsVariant Cell Globin Gene Single Amino Acid Substitution Flow Sorter Germinal Mutation
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