Restriction fragment analysis of duplication of the fourth component of complement (C4A)

Robert H. McLean, Patricia A. Donohoue, Nicholas Jospe, Wilma B. Bias, Cornelis Van Dop, Claude J. Migeon

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Abstract

The two genes encoding the fourth component of complement (C4A and C4B) reside between HLA-B and HLA-DR on human chromosome 6. Two kilobases downstream from each C4 gene lies a 21-hydroxylase gene (CA21HA and CA21HB, respectively). Utilizing the method of Southern blotting and a 5′-end 2.4-kb BamHI KpnI fragment of the C4 cDNA, we have analyzed TaqI-digested DNA from four pedigrees with one or more extended haplotypes containing a C4A duplication, as demonstrated by protein electrophoresis and segregation analysis. Two C4A protein duplications (C4A*2,A*3,C4B*QO and C4A*3,A*5,C4B*QO) segregated with two large TaqI DNA restriction fragments (7.0 and 6.0). In pedigree Fi, one individual homozygous for HLA-A3,B35,C4,DR1,DQ1,BFF,C2C,C4A2,3,C4BQO had TaqI 7.0- and 6.0-kb restriction fragments with equal hybridization intensities as measured by two-dimensional densitometry ( 7.0 6.0 kb = 0.83, SD = 0.12, N = 7). A hybridization probe for the 21-hydroxylase gene also demonstrated equal gene dosage ( CA21HA CA21HB = 1.01). DNA from another individual (Ma I-2) with a different C4A gene duplication (C4A*3,A*5,C4B*QO) also had equal densitometry measurements ( 7.0 6.0 kb = 1.07). We conclude that two extended haplotypes from unrelated pedigrees have two C4 genes and both C4 genes encode separate C4A alleles. These findings are compatible with a gene conversion event of C4B to C4A.

Original languageEnglish (US)
Pages (from-to)76-85
Number of pages10
JournalGenomics
Volume2
Issue number1
DOIs
StatePublished - Jan 1988

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ASJC Scopus subject areas

  • Genetics

Cite this

McLean, R. H., Donohoue, P. A., Jospe, N., Bias, W. B., Van Dop, C., & Migeon, C. J. (1988). Restriction fragment analysis of duplication of the fourth component of complement (C4A). Genomics, 2(1), 76-85. https://doi.org/10.1016/0888-7543(88)90111-5