Changes in alpha-globin gene expression in mice of two alpha-globin haplotypes during development.

Adult alpha-globin in mice is synthesized in large amounts during development, first in the primitive, nucleated erythrocytes of yolk sac origin and later in the definitive, nonnucleated erythrocytes that differentiate in the fetal liver, spleen, and bone marrow. Isoelectric focusing analysis of hemoglobins of mice with the Hbag2 and Hbac haplotypes shows that the ratios of alpha chain 1 to chain 5m and alpha chain 1 to chain 4 in adult hemoglobins from Hbag2 and Hbac mice, respectively, change between day 11.5 and day 16.5 of gestation in nucleated red cells, while no change occurs in nonnucleated red cells. The percentage ratios of the two different alpha-globin chains are different in Hbag2 and Hbac mice for EII, EIII, and adult hemoglobin. In nucleated red cells of yolk sac origin, differences and changes in alpha-globin ratios are a composite of changing globin gene transcription and posttranslational competitive affinities among globins to form embryonic and adult hemoglobin tetramers.