The KLF1 transcription factor regulates nearly all aspects of erythroid differentiation including heme synthesis and globin regulation.Previously,in collaborative studies with Dr.James Bieker (New York,NY),we showed that the inbred mouse model Nan (neonatal anemia) carries a missense mutation (E339D) in the second zinc finger of KLF1 that causes severe lifelong anemia in heterozygotes accompanied by a striking failure of hemoglobin switching.