Analysis of HLA class II haplotypes in the Cayapa Indians of Ecuador: a novel DRB1 allele reveals evidence for convergent evolution and balancing selection at position 86.

摘要: Abstract PCR amplification, oligonucleotide probe typing, and sequencing were used to analyze the HLA class II loci (DRB1, DQA1, DQB1, DPB1) of an isolated South Amerindian tribe. Here we report variation, including identification a new DRB1 allele, several novel DR/DQ haplotypes, unusual distribution DPB1 alleles, among Cayapa Indians (N = 100) Ecuador. A general reduction allelic variation in is consistent with population bottle-neck during colonization Americas. The DRB1*08042, which arose by G-->T point mutation parental DRB1*0802, contains Val codon (GTT) at position 86. generation DRB1*08042 (Val-86) from DRB1*0802 (Gly-86) Cayapa, different mechanism than (GT-->TG) change creation DRB1*08041 Africa, implicates selection convergent evolution 86 DR beta variants. allele has not been found > 1,800 haplotypes thus presumably after separated other American Amerindians. Selection pressure for increased haplotype diversity can be inferred maintenance three this population. also extraordinary, two DPB1*1401, very rare North populations, DPB1*0402, most common constituting 89% DPB1.(ABSTRACT TRUNCATED AT 250 WORDS)