ANALYSIS OF COMPLEMENT RECEPTOR-TYPE-1 (CRI) EXPRESSION ON ERYTHROCYTES AND OF CR-1 ALLELIC MARKERS IN CAUCASIAN AND AFRICAN-AMERICAN POPULATIONS

CR1 expression on erythrocytes (E) is regulated by an element that is tightly linked in Caucasians to the site of an RFLP of the CR1 gene. G enomic HindIII fragments of 7.4 and 6.9 kb identify alleles that are e xpressed in high (H allele) or low (L allele) amounts, respectively. W hen age-fractionated E of donors heterozygous for both the H and L all eles and for CR1 allotypes of differing molecular weights were analyze d in Western blots, the product of the L allele appeared to have an in creased rate of loss during cell aging A coding sequence polymorphism of CR1 predicted to cause a Pro --> Arg substitution in its proximal e xtramembranous region was tightly linked in Caucasians to the site of the HindIII RFLP. However, neither this polymorphism nor the HindlII R FLP correlated with CR1 expression among African Americans, Relative i nstability of CR1 encoded by the L allele thus may derive from another coding sequence polymorphism, or may require both the Pro --> Arg sub stitution and epistatic effects of another polymorphic gene. (C) 1998 Academic Press.