HUMAN-C4 HAPLOTYPES WITH DUPLICATED C4A OR C4B

  • 1 January 1984
    • journal article
    • research article
    • Vol. 36  (1) , 72-79
Abstract
In the course of study of families for the 6th chromosome markers HLA-A, C, B, D/DR, and C2, the 2 loci for C4, C4A and C4B, and glyoxalase I [GLO1], 5 examples of probable duplication of one or the other of the 2 loci for C4 were encountered. In one of these, both parents and 1 sib expressed 2 different structural genes for C4B, 1 sib expressed one, and 1 sib expressed none, suggesting that 2 C4B alleles were carried on a single haplotype: HLA-A2, B7, DR3, BFS1, C2C, C4A2, C4B1, C4B2, GLO1. In a 2nd case, 2 siblings inherited C4B*1 and C4B*2 from 1 parent and C4B*Q0 from the other. This duplication appeared on the chromosomes HLA-AW33, B14, DR1, BFS, C2C, C4A2, C4B1, C4B1, C4B2, GLO2. In a 3rd, very large family with 3 generations, a duplication of the C4B locus occurred which was followed in 2 generations. In 1 individual, there were 3 C4B alleles and 2 C4A alleles. One of the C4B alleles had a hemolytically active product with electrophoretic mobility near C4B2 and was designated C4B*22. It segregated with C4B1 in the family studied. The complete haplotype was HLA-A11, CW1, BW56, DR5, BFS, C2C, C4A3, C4B22, C4B1, GLO2. In another family with 12 siblings, 1 parent and 8 children expressed 2 C4A alleles on the haplotype HLA-AW30, BW38, DR1, BBF, C2C, C4A3, C4A2, C4BQ0, GLO1. In a 5th family, a duplication of the C4A locus was found on the haplotype HLA-A3, CW4, BW35, DR1, BFF, C2C, C4A3, C4A2, C4BQ0, GLO2. Thus, duplications of C4A and C4B loci were found on several different haplotypes. These are postulated to have arisen by unequal crossing over between the tandemly duplicated loci of C4.