Regulation of globin gene switch by nuclear transport processes of transcription factors

Sickle cell anemia is one of the most common genetic diseases worldwide and currently, cure can only be achieved with bone marrow transplantation when histocompatible donors are available. Here, we explore the possibility of correcting the defect of this disease by using embryonic stem (ES) cells. We have previously constructed a transgenic/knockout sickle cell anemia mouse that carries a 240 kb human h-globin gene cluster containing the sickle cell mutation (hS). We generated ES cells from this mouse and used homologous recombination with DNA constructs that contained the hA-globin gene to produce ES cells in which the hS globin genewas converted tohA sequence in one allele. Hematopoietic cells differentiated in vitro from these ES cells produced both hemoglobin A and hemoglobin S. By injecting the corrected ES cells into blastocysts of C57B/6 mice, we generated several chimeras in which various fractions of human Hb could be detected with the endogenous mouse Hb in their peripheral blood. One of the chimeras expressed the human Hb at a level of approximately 20% of the total Hb, and upon deoxygenation, 20% of the red cells showed sickling. However, at the ambient atmosphere, no sickle cells were visible in this chimeric mouse, suggesting that the introduced hA sequence was able to correct sickle cell anemia phenotype. Production of mice with the corrected hA genotype and attempt to cure the sickle cell disease by transplantation in our mouse model are in progress.