MIGRATION OF A NOVEL DQA1-ASTERISK ALLELE (DQA1-ASTERISK-0502) FROM AFRICAN ORIGIN TO NORTH AND SOUTH-AMERICA

A PCR-based strategy termed DHDA has recently been developed which rev eals DQA1 and DQB1 allelic polymorphism through gel retardation follow ing electrophoresis. This HLA-typing strategy improves the efficiency of identifying previously undetected DNA sequence polymorphisms. DHDA has been utilized to perform DQA1 genotypic analysis in non-Caucasian populations and has resulted in the identification of a novel allele, DQA10502 (designated by the WHO nomenclature committee). This new all ele has been found in Africans and South and North Americans of black racial ancestry and is geographically consistent with the African dias pora during the 15th-19th centuries. DQA10502 represents a single C-t o-G transversion in codon 59 (exon 2) and results in an amino acid cha nge from proline to arginine. Although MHC genes are highly polymorphi c, this DQA10502 substitution is unique, as it represents an amino ac id change at a position assessed previously to be conserved in the hum an DQ alpha polypeptides.