Isoelectric focusing and immunoblotting reveals considerable biochemical and genetic variation in the C1R subcomponent of the first complement component. The nature of the intraindividual biochemical variation can be explained by differences in sialic acid content because after digestion with neuraminidase the terminal sialic acids are removed to yield a single major band corresponding to the C1R polypeptide. Plasma samples from a large number of different ethnic groups, consisting of U.S. whites, U.S. blacks, Nigerian blacks, and Inuit, Aleut, and Amerindian populations from the Western Hemisphere have revealed genetically determined charge variation with heterozygous phenotypes consisting of two major asialo bands, indicating that the underlying variation is not due to variation in sialic acid content. Two previously reported common alleles, C1R*1 and C1R*2, have been observed in all studied populations, the notable exception being the Dogrib Indian population, which is devoid of the C1R*2 allele. Several new alleles - designated C1R*3, C1R*4, C1R*5, C1R*6, and C1R*7 - have been observed, with variable frequencies ranging from the occurrence in a single individual and related family members to the polymorphic occurrence of certain alleles in several populations. Of these new alleles, the C1R*5 is of considerable interest in population and anthropological genetics studies. The C1R*5 allele is widely distributed, at a frequency of .03 to .17, in all of the North American aboriginal populations screened. This allele is not present in U.S. whites but is present at a polymorphic frequency in U.S. and Nigerian blacks. The occurrence of the electrophoretically identical C1R*5 allele at polymorphic frequency in North American aboriginals and sporadically in populations of African origin raises interesting questions regarding the origin and possible heterogeneity of this allele.
|Original language||English (US)|
|Number of pages||8|
|Journal||American Journal of Human Genetics|
|State||Published - 1989|
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