title: Krüppel-Like Transcription Factor KLF1 Is Required for Optimal γ- and β-Globin Expression in Human Fetal Erythroblasts.
abstract: 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.
authors: Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America.
authors: Divya S
authors: DS
authors: Vinjamur
authors: Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America.
authors: Yousef N
authors: YN
authors: Alhashem
authors: Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America.
authors: Safa F
authors: SF
authors: Mohamad
authors: Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America.
authors: Parth
authors: P
authors: Amin
authors: Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia, United States of America.|Department of Pathology, Virginia Commonwealth University, Richmond, Virginia, United States of America.
authors: David C
authors: DC
authors: Williams
authors: Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America.|Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia, United States of America.
authors: Joyce A
authors: JA
authors: Lloyd
mesh_terms: D002352:Carrier Proteins / Q000502:physiology; D004900:Erythroblasts / Q000378:metabolism*; D005312:Fetal Blood; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D006801:Humans; D017578:Immunoglobulin Class Switching / Q000235:genetics; D051741:Kruppel-Like Transcription Factors / Q000502:physiology*; D009687:Nuclear Proteins / Q000502:physiology; D012097:Repressor Proteins; D055544:beta-Globins / Q000235:genetics*; D055545:gamma-Globins / Q000235:genetics*
chemical_list: C486563:BCL11A protein, human; D002352:Carrier Proteins; D051741:Kruppel-Like Transcription Factors; D009687:Nuclear Proteins; D012097:Repressor Proteins; D055544:beta-Globins; C080774:erythroid Kruppel-like factor; D055545:gamma-Globins