MUTANT HEMOGLOBINS THAT ALLOW HBS TO SICKLE

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A colony of mice will be produced that has hemoglobin with oxygen association-dissociation properties that are similar to human sickle cell hemoglobin (HbS). This will be done by breeding a stock of mice that carry two mutations at the hemoglobin loci. Mice that are homozygous for the Hbag2 alpha-globin haplotype will be mated with mice that are homozygous for the Hbbs2 beta-globin haplotype. F2 progeny will be screened to identify mice that are doubly homozygous for the alpha- and beta-globin gene mutations. The hemoglobin of Hbag2/Hbag2;Hbbs2/Hbbs2 mice will have oxygen association-dissociation properties similar to that of Hbs. The mice will be called MHOAH. MHOAH mice will be made transgenic for the human alpha- and sickle cell or sickle cell Antilles beta- globin genes to produce a transgenic mouse model for sickle cell disease. The transgenes will be introduced into MHOAH mice directly by breeding with stocks of mice that carry the transgenes or directly by microinjecting minilocus constructs of DNA into the male pronucleus of fertilized eggs of MHOAH mice. Mice that carry the transgenes will be identified by Southern blotting. Transgenic mice that express high levels of the transgenes will be identified by electrophoresis of blood hemolysates. The oxygen association- dissociation and gelation properties of hemoglobins in MHOAH mice that express high levels of HbS or HbS Antilles will be studied. Transgenic mice that express high levels of HbS Antilles are very likely to be an animal model for sickle cell disease. HbS Antilles has a lower solubility and a lower oxygen affinity than HbS. About 60 percent of the HbS Antilles will be deoxygenated at 40 mm of Hg oxygen tension; only 25 percent of the high oxygen affinity hemoglobin of MHOAH mouse would be deoxygenated at the same oxygen tension. These conditions produce sickle cell disease in HbA/S Antilles heterozygotes and are likely to produce gelation of HbS Antilles and sickling of erythrocytes in transgenic MHOAH mice. The mouse model for sickle cell anemia would facilitate research on the pathophysiology of the disease and on the development and testing of anti-sickling drugs.