The c.[833C; 844_845ins68] is a common haplotype of the human cystathionine beta-synthase gene among healthy individuals. This polymorphism (5-40% allelic frequency in different populations) consists of the c.844_845ins68 insertion that segregates in cis with the pathogenic c.833T>C substitution (p.I278T). Through genotyping of primates, we have found that gorillas, chimpanzees and bonobos are homozygous for the 68bp insertion, c.844_845ins68. In gorillas and bonobos, the c.844_845ins68 lesion segregates in cis with the wild-type c.833T variant, whilst chimpanzees present the human haplotype. These genetic evidences suggest that the origin of the 68bp insertion might be dated back to 6-8 million years ago, and that the c.833T>C substitution occurred within the allele carrying the insertion. The evolutionary conservation of this peculiar haplotype supports the hypothesis of its protective effects against cardiovascular diseases.
