Polymorphism of C4 and CYP21 genes in various primate species.

To study the genetic heterogeneity of the C4 and CYP21 genes in selected primate species we used the technique of restriction fragment length polymorphism (RFLP). Genomic DNA was digested using several restriction endonucleases and filters were hybridized with a 500 bp BamHI/KpnI fragment derived from the 5' section of a human C4-cDNA and with a 1700 bp BamHI obtained from a human CYP21 gene. Abundant RFLP heterogeneity was observed for the C4 genes within a rhesus monkey population but not for the chimpanzee colony analyzed. Duplicated C4-CYP21 clusters can be traced back in humans, but also in chimpanzees, orang-utans and rhesus monkeys. Thus, duplication of the basic C4-CYP21 cluster in primates may have happened more than 30 million years ago. Non-duplicated C4-CYP21 regions were found for the gorilla and orang-utan. Apart from this, shortened C4A and C4B genes were observed in chimpanzees, orang-utans and rhesus monkeys, whereas the so-called long variety of the C4A gene appears to be present in humans and orang-utans. This ancestral modification, resulting from an insertion of a 6.5 kb intron in the C4A gene, therefore predates at least speciation of human and orang-utan which is estimated to have taken place more than 12 million years ago.