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Available from: Joseph Borg, Mar 19, 2014
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    • "transcription factor genes in both primitive and definitive erythroid cells (Siatecka and Bieker, 2011; Tallack and Perkins, 2010; Yien and Bieker, 2013). Relatedly, links have been established between mutant or haploinsufficient levels of EKLF and altered human hematology and anemia (Borg et al., 2011; Helias et al., 2013; Siatecka and Bieker, 2011; Singleton et al., 2012). Comparative analysis of expression arrays between EKLF wildtype and EKLF-null fetal liver cells show that a number of genes involved in execution of the terminal erythroid differentiation program are downregulated in the absence of EKLF (Drissen et al., 2005; Hodge et al., 2006; Pilon et al., 2006, 2011; Tallack et al., 2012, 2010). "
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    ABSTRACT: KLF1 is an erythroid specific transcription factor that is involved in erythroid lineage commitment, globin switching and terminal red blood cell maturation. Various mutations of KLF1 have been identified in humans, which have led to both benign and pathological phenotypes. The E325K mutation, within the second zinc finger of the KLF1 gene, has been shown to cause a new form of congenital dyserythropoietic anemia (CDA) now labeled as CDA type IV. We report the fourth documented case of this mutation, and propose a clinical diagnostic model to better identify this disease in other patients. Our patient is a Taiwanese child who presented to us at 8years of age with severe hemolytic anemia, splenomegaly, elevated fetal hemoglobin (HbF), iron overload, and dyserythropoiesis in the bone marrow. KLF1 sequence analysis revealed a G-to-A transition in one allele of exon 3, which resulted in the substitution of a glutamate 325 by a lysine. Flow cytometry analysis revealed decreased protein expression of CD44 on the red blood cells, and decreased red blood cell deformability as measured using an ektacytometer. Blood typing revealed his red blood cells to be Co(a-b-), In(b-), LW(ab-) and Lu(b+), even though DNA testing predicted that he would be Co(a+b-) and LW(a+b-). This newly discovered CDA combines features of a hemoglobinopathy, RBC membrane defect and hereditary persistence of HbF (HPFH) which are not seen in the previous types of CDA. Increased awareness of this phenotype may improve the more prompt and accurate diagnosis of these patients.
    Blood Cells Molecules and Diseases 03/2013; 51(2). DOI:10.1016/j.bcmd.2013.02.006 · 2.65 Impact Factor
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    • "Extensive studies have correlated expression of KLF1 and that of numerous erythroid-restricted genes required for progenitor proliferation and differentiation, including cell cycle regulators, synthetic enzymes, and components of the unique membrane and cytoskeletal structures of the mature erythrocyte [13], [14], [15], [16], [17]. Structure-function studies of naturally occurring and experimental KLF1 mutants reveal variable effects on these KLF1-dependent non-globin promoters, that differ significantly from those observed at the β-globin gene [18], [19], [20], [21], [22]. Together, these observations suggest that studies of KLF1 action at non-globin genes may delineate context-specific mechanism(s) of action of this factor, and provide insights into key targets required for effective erythropoiesis. "
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    ABSTRACT: Krüppel-like factor 1(KLF1) is a hematopoietic-specific zinc finger transcription factor essential for erythroid gene expression. In concert with the transacting factor GATA1, KLF1 modulates the coordinate expression of the genes encoding the multi-enzyme heme biosynthetic pathway during erythroid differentiation. To explore the mechanisms underpinning KLF1 action at the gene loci regulating the first 3 steps in this process, we have exploited the K1-ERp erythroid cell line, in which KLF1 translocates rapidly to the nucleus in response to treatment with 4-OH-Tamoxifen (4-OHT). KLF1 acts as a differentiation-independent transcriptional co-regulator of delta-aminolevulinic acid dehydratase (Alad), but not 5-aminolevulinate synthase gene (Alas2) or porphobilinogen deaminase (Pbgd). Similar to its role at the β-globin promoter, KLF1 induces factor recruitment and chromatin changes at the Alad1b promoter in a temporally-specific manner. In contrast to these changes, we observed a distinct mechanism of histone eviction at the Alad1b promoter. Furthermore, KLF1-dependent events were not modulated by GATA1 factor promoter co-occupancy alone. These results not only enhance our understanding of erythroid-specific modulation of heme biosynthetic regulation by KLF1, but provide a model that will facilitate the elucidation of novel KLF1-dependent events at erythroid gene loci that are independent of GATA1 activity.
    PLoS ONE 10/2012; 7(10):e46482. DOI:10.1371/journal.pone.0046482 · 3.23 Impact Factor
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    ABSTRACT: Erythropoiesis is dependent on the activity of transcription factors, including the erythroid-specific erythroid Kruppel-like factor (EKLF). ChIP followed by massively parallel sequencing (ChIP-Seq) is a powerful, unbiased method to map trans-factor occupancy. We used ChIP-Seq to study the interactome of EKLF in mouse erythroid progenitor cells and more differentiated erythroblasts. We correlated these results with the nuclear distribution of EKLF, RNA-Seq analysis of the transcriptome, and the occupancy of other erythroid transcription factors. In progenitor cells, EKLF is found predominantly at the periphery of the nucleus, where EKLF primarily occupies the promoter regions of genes and acts as a transcriptional activator. In erythroblasts, EKLF is distributed throughout the nucleus, and erythroblast-specific EKLF occupancy is predominantly in intragenic regions. In progenitor cells, EKLF modulates general cell growth and cell cycle regulatory pathways, whereas in erythroblasts EKLF is associated with repression of these pathways. The EKLF interactome shows very little overlap with the interactomes of GATA1, GATA2, or TAL1, leading to a model in which EKLF directs programs that are independent of those regulated by the GATA factors or TAL1.
    Blood 09/2011; 118(17):e139-48. DOI:10.1182/blood-2011-05-355107 · 10.45 Impact Factor
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