Severe anemia in theNanmutant mouse caused by sequence-selective disruption of erythroid Krüppel-like factor

Abstract

Studies of mouse models of anemia have long provided fundamental insights into red blood cell formation and function. Here we show that the semidominant mouse mutation Nan (“neonatal anemia”) carries a single amino acid change (E339D) within the second zinc finger of the erythroid Krüppel-like factor (EKLF), a critical erythroid regulatory transcription factor. The mutation alters the DNA-binding specificity of EKLF so that it no longer binds promoters of a subset of its DNA targets. Remarkably, even when mutant Nan and wild-type EKLF alleles are expressed at equivalent levels, the mutant form selectively interferes with expression of EKLF target genes whose promoter elements it no longer binds. This interference yields a distorted genetic output and selective protein deficiencies that differ from those seen in EKLF-heterozygous and EKLF-null red blood cells and presents a unique and unexpected mechanism of inherited disease.

Erythroid phenotypes associated with KLF1 mutations

“…Remarkably, an ethylnitrosourea-induced mutation in the homologous position in mouse KLF1 causes the dominant Nan (neonatal anemia) phenotype. [16][17] Heterozygous Nan/+ mice displayed hereditary spherocytosis and severe hemolytic anemia. Expression of erythrocyte membrane skeleton proteins and β-globin was reduced, but embryonic globins were present at aberrantly high levels (Figures 1 and 3).…”

“…The mutation, p.E339D, reduced binding to a subset of KLF1 binding sites, and this selectively affected activation of KLF1 target genes. 17 The variant residues have opposite charges: positive in the CAD patients (p.E325K, lysine) and negative in the Nan mouse (p.E339D, aspartic acid). These mutants have different DNA binding properties that determine the impact on the expression of KLF1 target genes.…”

“…These mutants have different DNA binding properties that determine the impact on the expression of KLF1 target genes. 15,17 Thus, different KLF1 missense mutations that affect DNA binding properties could well lead to distinct red cell disorders 15 ( Figure 3). …”

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

“…23 The ethylnitrosurea-induced mouse mutant Nan (neonatal anemia) carries a missense mutation, p.E339D, in the homologous position of mouse KLF1. 39,40 This mutation causes a dominant hemolytic anemia, with markedly increased expression of embryonic globins in adult Nan animals. 40 Collectively, these data support a model in which KLF1 activates b-globin expression and suppresses the embryonic/fetal b-like globin genes.…”

“…39,40 This mutation causes a dominant hemolytic anemia, with markedly increased expression of embryonic globins in adult Nan animals. 40 Collectively, these data support a model in which KLF1 activates b-globin expression and suppresses the embryonic/fetal b-like globin genes. Recently, it has been shown that expression of BCL11A is regulated by KLF1, suggesting an intricate mechanism for the developmental regulation of the b-like globin genes coordinately mediated by KLF1 and BCL11A.…”