Major erythrocyte membrane protein genes in EKLF-deficient mice

Objectives Mice deficient in the transcription factor erythroid Krüppel-like factor, KLF1 (EKLF) die not, vert, similar14.5 days postcoitum of anemia, attributed to decreased expression of the β-globin gene. The objectives of this study were to rescue EKLF-deficient embryos with mice expressing γ-globin from β-spectrin or ankyrin promoters and to characterize expression of the major erythrocyte membrane genes in EKLF-deficient cells. Methods Transgenic β-spectrin/γ-globin or ankyrin/γ-globin mice were bred onto EKLF-deficient and wild-type backgrounds. Animals were genotyped, γ-globin mRNA levels measured, and hemoglobin electrophoresis performed. Steady-state mRNA levels and transcriptional rates of the major erythrocyte membrane protein genes were assayed. Results β-spectrin/γ-globin or ankyrin/γ-globin mice on EKLF-deficient and wild-type backgrounds had identical levels of γ-globin mRNA, indicating EKLF-independence of these promoters. γ-Globin expression improved globin chain imbalance, but hemolysis was not improved and no live-born EKLF-deficient/Aγ-globin mice were obtained. Circulating erythroid cells from EKLF-deficient/Aγ-globin embryos exhibited hemolysis reminiscent of that seen in patients with severe erythrocyte membrane defects. Levels of β-spectrin, ankyrin, and band 3 mRNA, but not α-spectrin, were decreased in EKLF-deficient fetal liver RNA. In a run-on assay, levels of transcription of the ankyrin and band 3 genes were decreased in EKLF-deficient fetal liver nuclei. Conclusions These results indicate that the EKLF-responsive regions of the ankyrin and β-spectrin genes are outside their promoters and that EKLF is necessary for full transcriptional activity of the ankyrin and band 3 genes; the results also provide additional evidence that defects in addition to β-globin deficiency, including an abnormal erythrocyte membrane, contribute to the anemia and embryonic lethality in EKLF-deficient mice.