The proposed research seeks to isolate DNA regions important in the genetic control of the differential synthesis of human fetal and adult hemoglobins and of the distribution of fetal hemoglobin in red cell populations. Heterozygotes for the Hb Lepore deletion chromosome G gamma A gamma delta-(Deletion)-beta, have thalassemia minor-like red cells with HbF, (G gamma and A gamma), in a minority red cell population. Heterozygotes for the Hb Kenya deletion, G gamma gamma-(Deletion)-beta, have normal red cells with HbF, (G gamma), in all their cells. This strongly suggests the existence of important and different cis-acting control elements in the DNA between these several structural genes. Consequently we plan to isolate, by molecular cloning, the DNA corresponding to the G gamma A gamma delta beta region of the human genome and to compare the structures of the intergenic control regions. Embryonic human DNA will be randomly sheared or digested with restriction enzymes and the globin gene-containing fragments will be enriched by recycling chromatography over a column of cloned mouse beta-globin cDNA isolated in our preliminary work. A method of cloning these globin-enriched genomic fragments with a specially constructed bacteriophage lambda will be used which requires that the cloned DNA contains globin gene sequences before the phage will grow. Further selectivity will be built into the system by using a cloned probe that will give positive results only when a new clone is longer than the starting clone. In this way, overlapping clones covering the desired genomic region will be accumulated. The structure of the cloned intergenic regions will be compare by restriction mapping, electron-microscopic heteroduplexing, cross-hybridization testing and by partial DNA sequencing. The general structure of DNA from this globin region will also be examined in patients with genetic abnormalities in hemoglobin synthesis.
NIH ExPorter
NIH ExPorter