Extensive studies during the last 30 years have led to considerable understanding of cellular
and molecular control of hemoglobin switching. Cell biology studies in the 1970s defined the
control of globin genes during erythroid differentiation and led to development of therapies
for sickle cell disease. Molecular investigations of the last 20 years have delineated the two
basic mechanisms that control globin gene activity during development—autonomous
silencing and gene competition. Studies of hemoglobin switching have provided major …