Project description:Boontanrart et al model the cellular stress that occurs upon reduction in β-globin in human erythroid cells. Decrease in β-globin attenuates the eIF2aP-ATF4 pathway and results in upregulating fetal -globin. Down-regulation of ATF4 leads to decreased levels of the -globin repressor MYB through direct binding at the HBS1L-MYB intergenic region.
Project description:Boontanrart et al model the cellular stress that occurs upon reduction in β-globin in human erythroid cells. Decrease in β-globin attenuates the eIF2aP-ATF4 pathway and results in upregulating fetal g-globin. Down-regulation of ATF4 leads to decreased levels of the g-globin repressor MYB through direct binding at the HBS1L-MYB intergenic region.
Project description:Through a CRISPR-Cas9 guided loss-of-function screen in human erythroid cells we identified transcription factor ATF4, a known HRI-regulated protein, as a novel γ-globin repressor. ATF4 binds to a BCL11A enhancer to augment promoter contacts, stimulates BCL11A transcription to repress γ-globin expression. Notably, mice deficient for HRI displayed normal Bcl11a levels, suggesting species selective regulation that we explain here by demonstrating that the analogous ATF4 motif at the murine Bcl11a enhancer is largely dispensable. This illustrates potential limits of commonly used murine models of globin gene regulation.
Project description:Through a CRISPR-Cas9 guided loss-of-function screen in human erythroid cells we identified transcription factor ATF4, a known HRI-regulated protein, as a novel γ-globin repressor. ATF4 binds to a BCL11A enhancer to augment promoter contacts, stimulates BCL11A transcription to repress γ-globin expression. Notably, mice deficient for HRI displayed normal Bcl11a levels, suggesting species selective regulation that we explain here by demonstrating that the analogous ATF4 motif at the murine Bcl11a enhancer is largely dispensable. This illustrates potential limits of commonly used murine models of globin gene regulation.
Project description:MYB plays a critical role as a regulator of erythropoieisis. We have shown that MYB silences epsilon and gamma-globin expression in erythroid progenitors. We here examine erythroid cells at the basophilic erythroblast stage of differentiation with MYB shRNA or control lentiviral transduction prior to differentiation.
Project description:MYB plays a critical role as a regulator of erythropoieisis. We have shown that MYB silences epsilon and gamma-globin expression in erythroid progenitors. We here examine erythroid cells at the basophilic erythroblast stage of differentiation with MYB shRNA or control lentiviral transduction prior to differentiation. We have cultured CD34 cells and transduced the cells with lentiviruses harboring shRNAs targeting MYB or controls and then allowed the cells to differentiate down the erythroid lineage. At the basophilic erythroblast stage of differentiation, the cells were harvested and total RNA was extracted. This was used to hybridize to Affymetrix expression arrays using the HG-U133 Plus 2.0 platform to ascertain expression differences that occur with the knockdown of MYB.
Project description:Human embryonic stem cells provide an alternative to using human embryos for studying developmentally regulated gene expression. The co-expression of high levels of embryonic epsilon and fetal gamma globin by the hESC-derived erythroblasts allows the interrogation of epsilon globin regulation at the transcriptional and epigenetic level which could only be attained previously by studying cell lines or transgenic mice. In this study, we compared the histone modifications across the beta globin locus of the undifferentiated hESCs and hESC-, FL-, and mobilized PB CD34+ cells-derived erythroblasts, which have distinct globin expression patterns corresponding to their developmental stages. We demonstrated that the histone codes employed by the beta globin locus are conserved throughout development. Furthermore, in spite of the close proximity of the epsilon globin promoter, as compared to the gamma or beta globin promoter, with the LCR, a chromatin loop was also formed between the LCR and the active epsilon globin promoter, similar to the loop that forms between the gamma or beta globin promoters and the LCR, in contrary to the previously proposed tracking mechanism. Human embryonic stem cells, hESC-, FL-, and PB derived erythroblasts were studied. The enrichment of H3K4me3 and AcH3 acrossed the beta globin locus was studied using ChIP-seq.