Advisory Committee Chair
Thomas M Ryan
Advisory Committee Members
Christopher A Klug
Anupam Agarwal
Ching-Yi Chen
Tim M Townes
Document Type
Dissertation
Date of Award
2011
Degree Name by School
Doctor of Philosophy (PhD) Heersink School of Medicine
Abstract
The mammalian erythrocyte is a highly specialized blood cell that differentiates via an orderly series of committed progenitors in the bone marrow in a process termed erythropoiesis. During erythroid development, hemoglobin synthesis increases from early erythroid progenitors to mature enucleated red blood cells (RBCs). Although hemoglobin is the most extensively studied protein in history, the role, if any, that hemoglobin plays in erythroid development remains obscure. In this study, I ask the question what happens during erythropoiesis in the absence of hemoglobin. I demonstrate that my original hypothesis that excess free heme would accumulate in the absence of globin chain production resulting in the early death of erythroid progenitors is incorrect. To test this hypothesis, mouse embryos and embryonic stem (ES) cells that have all their adult &alpha and &beta globin genes deleted (Hb Null) are generated and the Hb Null ES cells are used to produce Hb Null chimeric mice. I demonstrate that Hb Null embryos are extremely anemic, have a defect in their primitive erythropoiesis, and die in midgestation. Surprisingly, in Hb Null chimeric mice all stages of nucleated definitive erythroid development is normal, and Hb Null erythroid cells can even enucleate and form reticulocytes. Furthermore, the level of total heme in Hb Null erythoblasts is dramatically reduced. In chimeric mice the number of Hb Null reticulocytes is reduced more than 90%. Expression of the heme binding protein, human myoglobin, in Hb Null erythroid cells does not prevent reticulocyte loss. Bone marrow transplantation of donor Hb Null derived hematopoietic cells into lethally irradiated wild type mice results in reconstituted mice with pure Hb Null derived erythropoietic tissues and up to 1% Hb Null reticulocytes in the peripheral blood. These data suggest that hemoglobin reduction in erythroid cells unlikely causes free heme level elevation. This novel Hb Null model provides a unique experimental system to test future hypotheses on the role played by hemoglobin in erythroid cell enucleation, cytoskeleton maturation, and heme and iron regulation.
Recommended Citation
Liu, Shanrun, "ERYTHROPOIESIS IN THE ABSENCE OF ADULT HEMOGLOBIN" (2011). All ETDs from UAB. 2309.
https://digitalcommons.library.uab.edu/etd-collection/2309