Krüppel-Like Transcription Factor KLF1 Is Required for Optimal γ- and β-Globin Expression in Human Fetal Erythroblasts. 2016

Divya S Vinjamur, and Yousef N Alhashem, and Safa F Mohamad, and Parth Amin, and David C Williams, and Joyce A Lloyd
Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America.

In human adult erythroid cells, lower than normal levels of Krüppel-like transcription factor 1 (KLF1) are generally associated with decreased adult β- and increased fetal γ-globin gene expression. KLF1 also regulates BCL11A, a known repressor of adult γ-globin expression. In seeming contrast to the findings in adult cells, lower amounts of KLF1 correlate with both reduced embryonic and reduced fetal β-like globin mRNA in mouse embryonic erythroid cells. The role of KLF1 in primary human fetal erythroid cells, which express both γ- and β-globin mRNA, is less well understood. Therefore, we studied the role of KLF1 in ex vivo differentiated CD34+ umbilical cord blood cells (UCB erythroblasts), representing the fetal milieu. In UCB erythroblasts, KLF1 binds to the β-globin locus control region (LCR), and the β-globin promoter. There is very little KLF1 binding detectable at the γ-globin promoter. Correspondingly, when cultured fetal UCB erythroblasts are subjected to lentiviral KLF1 knockdown, the active histone mark H3K4me3 and RNA pol II recruitment are diminished at the β- but not the γ-globin gene. The amount of KLF1 expression strongly positively correlates with β-globin mRNA and weakly positively correlates with BCL11A mRNA. With modest KLF1 knockdown, mimicking haploinsufficiency, γ-globin mRNA is increased in UCB erythroblasts, as is common in adult cells. However, a threshold level of KLF1 is evidently required, or there is no absolute increase in γ-globin mRNA in UCB erythroblasts. Therefore, the role of KLF1 in γ-globin regulation in fetal erythroblasts is complex, with both positive and negative facets. Furthermore, in UCB erythroblasts, diminished BCL11A is not sufficient to induce γ-globin in the absence of KLF1. These findings have implications for the manipulation of BCL11A and/or KLF1 to induce γ-globin for therapy of the β-hemoglobinopathies.

UI MeSH Term Description Entries
D009687 Nuclear Proteins Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus. Nucleolar Protein,Nucleolar Proteins,Nuclear Protein,Protein, Nuclear,Protein, Nucleolar,Proteins, Nuclear,Proteins, Nucleolar
D012097 Repressor Proteins Proteins which maintain the transcriptional quiescence of specific GENES or OPERONS. Classical repressor proteins are DNA-binding proteins that are normally bound to the OPERATOR REGION of an operon, or the ENHANCER SEQUENCES of a gene until a signal occurs that causes their release. Repressor Molecules,Transcriptional Silencing Factors,Proteins, Repressor,Silencing Factors, Transcriptional
D002352 Carrier Proteins Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes. Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D004900 Erythroblasts Immature, nucleated ERYTHROCYTES occupying the stage of ERYTHROPOIESIS that follows formation of ERYTHROID PRECURSOR CELLS and precedes formation of RETICULOCYTES. The normal series is called normoblasts. Cells called MEGALOBLASTS are a pathologic series of erythroblasts. Erythrocytes, Nucleated,Normoblasts,Proerythroblasts,Pronormoblasts,Erythroblast,Erythrocyte, Nucleated,Normoblast,Nucleated Erythrocyte,Nucleated Erythrocytes,Proerythroblast,Pronormoblast
D005312 Fetal Blood Blood of the fetus. Exchange of nutrients and waste between the fetal and maternal blood occurs via the PLACENTA. The cord blood is blood contained in the umbilical vessels (UMBILICAL CORD) at the time of delivery. Cord Blood,Umbilical Cord Blood,Blood, Cord,Blood, Fetal,Blood, Umbilical Cord,Bloods, Cord,Bloods, Fetal,Bloods, Umbilical Cord,Cord Blood, Umbilical,Cord Bloods,Cord Bloods, Umbilical,Fetal Bloods,Umbilical Cord Bloods
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D017578 Immunoglobulin Class Switching Gene rearrangement of the B-lymphocyte which results in a substitution in the type of heavy-chain constant region that is expressed. This allows the effector response to change while the antigen binding specificity (variable region) remains the same. The majority of class switching occurs by a DNA recombination event but it also can take place at the level of RNA processing. Class Switching,Ig Class Switching,Isotype Switching,Class Switching, Ig,Class Switching, Immunoglobulin,Class Switchings,Class Switchings, Ig,Class Switchings, Immunoglobulin,Ig Class Switchings,Immunoglobulin Class Switchings,Isotype Switchings,Switching, Class,Switching, Ig Class,Switching, Immunoglobulin Class,Switching, Isotype,Switchings, Class,Switchings, Ig Class,Switchings, Immunoglobulin Class,Switchings, Isotype
D051741 Kruppel-Like Transcription Factors A family of zinc finger transcription factors that share homology with Kruppel protein, Drosophila. They contain a highly conserved seven amino acid spacer sequence in between their ZINC FINGER MOTIFS. Kruppel-Like Factor,Kruppel-Like Transcription Factor,Kruppel-Like Factors,Factor, Kruppel-Like,Factor, Kruppel-Like Transcription,Kruppel Like Factor,Kruppel Like Factors,Kruppel Like Transcription Factor,Kruppel Like Transcription Factors,Transcription Factor, Kruppel-Like,Transcription Factors, Kruppel-Like
D055544 beta-Globins Members of the beta-globin family. In humans, they are encoded in a gene cluster on CHROMOSOME 11. They include epsilon-globin, gamma-globin, delta-globin and beta-globin. There is also a pseudogene of beta (theta-beta) in the gene cluster. Adult HEMOGLOBIN is comprised of two ALPHA-GLOBIN chains and two beta-globin chains. beta-Globin,Non-alpha Globin Chain, Unspecified,Non alpha Globin Chain, Unspecified,beta Globin,beta Globins
D055545 gamma-Globins Members of the beta-globin family. In humans, two non-allelic types of gamma-globin - A gamma and G gamma are encoded in the beta-globin gene cluster on CHROMOSOME 11. Two gamma-globin chains combine with two ZETA-GLOBIN chains to form the embryonic hemoglobin Portland. Fetal HEMOGLOBIN F is formed from two gamma-globin chains combined with two ALPHA-GLOBIN chains. gamma-Globin,A gamma-Globin,G gamma-Globin,A gamma Globin,G gamma Globin,gamma Globin,gamma Globins

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