Molecular cloning and variant analysis of the genes associated with Rh blood group antigens.

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Rhnull phenotypes, which lack all Rh antigens, were analyzed by molecular-genetic procedures and categorized into two groups by the genetic backgrounds; 'amorph type' results from abnormality of both RHCE and RHD genes and 'regulator type' results from abnormality of RH5O gene independent locus from RH. These results confirmed that Rh5O glycoprotein is an indispensable factor for the expression of Rh antigens on erythrocyte membrane. A erythroid cell line (KU812E) originally expressing Rh5O glycoprotein was transduced by retroviral vector encoding RhD or RhCE cDNAs. The cells transduced Rh cDNAs expressed the respective Rh antigens. On the contrary, non-erythroid cell line (HEK293) not expressing Rh5O glycoprotein failed to express Rh antigens on the plasma membrane despite the induction of both cDNAs of Rh and Rh5O. Immuno-electro-microscopic analysis of the induced cell lines revealed that the cell lines expressed Rh5O antigen on the cytoplasmic-organella membranes. It was suggested that non-erythroid cell lack the expression of erythroid specific factors other than Rh and Rh5O to express Rh antigens on the plasma membrane. Then, we have intended to induce further a human cDNA library established from bone marrow into the double transfected HEK293 and screen the induced cell stained by anti-Rh antibodies through cell-sorter. However, the cDNA clone which induce the expression of Rh antigens on the plasma membrane of non-erythroid is still under hunting. We also isolated the promoter region of RH50 gene and characterized it. Just 5' flanking sequence of RH5O gene has an inverse GATA motif which is critically involved in the erythroid specific promoter activity. An erythroid specific DNaseI hypersensitive site was identified in the further up-stream region, which also encoded an inverse GATA motif. These results support further the erythroid dominant expression of the RH5O gene.