The Human Complement Component C1R Gene: The Exon-intron Structure and the Molecular Basis of Allelic Diversity

Human C1r is a component of the complement system, which is a major mediator of innate immunity. In this study we investigated the exon‐intron organization of the human C1R gene, which spans 11 kb from the initiation codon to the stop codon, and is very similar in exon‐intron structure to the C1S gene. Six common and rare alleles, C1R*1, C1R*2, C1R*5, C1R*8, C1R*9, and C1R*13, were characterized by five mutations at amino acid positions 114, 135, 146, 167 and 244, in exons 4, 5 and 7 where the CUB1, EGF and CUB2 domains are encoded, respectively. A comparison with the cDNA of the mouse C1r gene showed that C1R*2is likely to be an ancestral allele. In addition, nine nucleotide substitutions and one length polymorphism were found in introns 2, 3, 4, 8 and 10.