Erythropoiesis and globin switching in compound Klf1::Bcl11a mutant mice.

B-cell lymphoma 11A (BCL11A) downregulation in human primary adult erythroid progenitors results in elevated expression of fetal γ-globin. Recent reports showed that BCL11A expression is activated by KLF1, leading to γ-globin repression. To study regulation of erythropoiesis and globin expression by KLF1 and BCL11A in an in vivo model, we used mice carrying a human β-globin locus transgene with combinations of Klf1 knockout, Bcl11a floxed, and EpoR(Cre) knockin alleles. We found a higher percentage of reticulocytes in adult Klf1(wt/ko) mice and a mild compensated anemia in Bcl11a(cko/cko) mice. These phenotypes were more pronounced in compound Klf1(wt/ko)::Bcl11a(cko/cko) mice. Analysis of Klf1(wt/ko), Bcl11a(cko/cko), and Klf1(wt/ko)::Bcl11a(cko/cko) mutant embryos demonstrated increased expression of mouse embryonic globins during fetal development. Expression of human γ-globin remained high in Bcl11a(cko/cko) embryos during fetal development, and this was further augmented in Klf1(wt/ko)::Bcl11a(cko/cko) embryos. After birth, expression of human γ-globin and mouse embryonic globins decreased in Bcl11a(cko/cko) and Klf1(wt/ko)::Bcl11a(cko/cko) mice, but the levels remained much higher than those observed in control animals. Collectively, our data support an important role for the KLF1-BCL11A axis in erythroid maturation and developmental regulation of globin expression.