The analysis of Rh antigen (polypeptide) function and the molecular evolution of orthologous RH genes in various species.

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The Rh blood group discovered by Levine and Stetson is clinically one of the most important blood groups similar to ABO system. It is indicated that the Rh system was encoded on two genes termed RHCE and RHD, which are closely linked, highly homologous and consist of ten exons each. The RH genes are located in chromosome 1p 34.3-36.1. Many serological investigations have revealed and a lot of variants such as D--, partial D and antigens from forty up were identified. The RHD and RHCE genes totalled 57295 bp and 57831 bp in length, respectively. It is thought that multiple recombination (and/or gene conversion), nucleotide substitutions, small nucleotide gaps, replication slippage of microsatellite, large nucleotide gaps (due to Alu sequence) and the high level of the homology(%) between both RH genes is the important factors in the formation and evolution of both RH genes and Rh variants.We analyzed weakD phenotypes, which are Rh variant, and reported the molecular genetic background of them. Due to the findings obtained by the analysis of these Rh variants(weakD), we speculated the mechanism of the expression of Rh antigen(polypeptide).It is presumed that human Rh family (superfamily) consists of the RH (RHCE and RHD), RHAG (RH5O), RHBG and RHGK (RHCG) genes. It is speculated that Rh superfamily is associated with ammonium transporter by biochemical evidence and Genbank search. The RH, RHAG and RHBG/RHGK genes derived from ammonium transporter might have independently followed different evolutionary pathways by our phylogenetic tree analysis(the neighbor-joining method).By analyzing the orthologous RH gene superfamily in pig, we determined the porcine RH and RHBG genes are mapped in pig chromosomes 6q22-q23 and 4q21-q22, respectively.