Hemoglobin-expressing erythrocytes (red blood cells) act as fundamental metabolic regulators by providing oxygen to cells and tissues throughout the body. Whereas the vital requirement for oxygen to ...support metabolically active cells and tissues is well established, almost nothing is known regarding how erythrocyte development and function impact regeneration. Furthermore, many questions remain unanswered relating to how insults to hematopoietic stem/progenitor cells and erythrocytes can trigger a massive regenerative process termed 'stress erythropoiesis' to produce billions of erythrocytes. Here, we review the cellular and molecular mechanisms governing erythrocyte development and regeneration, and discuss the potential links between these events and other regenerative processes.
Given the complexity of intracellular RNA ensembles and vast phenotypic remodeling intrinsic to cellular differentiation, it is instructive to consider the role of RNA regulatory machinery in ...controlling differentiation. Dynamic post-transcriptional regulation of protein-coding and non-coding transcripts is vital for establishing and maintaining proteomes that enable or oppose differentiation. By contrast to extensively studied transcriptional mechanisms governing differentiation, many questions remain unanswered regarding the involvement of post-transcriptional mechanisms. Through its catalytic activity to selectively process or degrade RNAs, the RNA exosome complex dictates the levels of RNAs comprising multiple RNA classes, thereby regulating chromatin structure, gene expression and differentiation. Although the RNA exosome would be expected to control diverse biological processes, studies to elucidate its biological functions and how it integrates into, or functions in parallel with, cell type-specific transcriptional mechanisms are in their infancy. Mechanistic analyses have demonstrated that the RNA exosome confers expression of a differentiation regulatory receptor tyrosine kinase, downregulates the telomerase RNA component TERC, confers genomic stability and promotes DNA repair, which have considerable physiological and pathological implications. In this review, we address how a broadly operational RNA regulatory complex interfaces with cell type-specific machinery to control cellular differentiation.
Developmental-regulatory networks often include large gene families encoding mechanistically-related proteins like G-protein-coupled receptors, zinc finger transcription factors and solute carrier ...(SLC) transporters. In principle, a common mechanism may confer expression of multiple members integral to a developmental process, or diverse mechanisms may be deployed. Using genetic complementation and enhancer-mutant systems, we analyzed the 456 member SLC family that establishes the small molecule constitution of cells. This analysis identified SLC gene cohorts regulated by GATA1 and/or GATA2 during erythroid differentiation. As >50 SLC genes shared GATA factor regulation, a common mechanism established multiple members of this family. These genes included Slc29a1 encoding an equilibrative nucleoside transporter (Slc29a1/ENT1) that utilizes adenosine as a preferred substrate. Slc29a1 promoted erythroblast survival and differentiation ex vivo. Targeted ablation of murine Slc29a1 in erythroblasts attenuated erythropoiesis and erythrocyte regeneration in response to acute anemia. Our results reveal a GATA factor-regulated SLC ensemble, with a nucleoside transporter component that promotes erythropoiesis and prevents anemia, and establish a mechanistic link between GATA factor and adenosine mechanisms. We propose that integration of the GATA factor-adenosine circuit with other components of the GATA factor-regulated SLC ensemble establishes the small molecule repertoire required for progenitor cells to efficiently generate erythrocytes.
Abstract
Cellular differentiation requires vast remodeling of transcriptomes, and therefore machinery mediating remodeling controls differentiation. Relative to transcriptional mechanisms governing ...differentiation, post-transcriptional processes are less well understood. As an important post-transcriptional determinant of transcriptomes, the RNA exosome complex (EC) mediates processing and/or degradation of select RNAs. During erythropoiesis, the erythroid transcription factor GATA1 represses EC subunit genes. Depleting EC structural subunits prior to GATA1-mediated repression is deleterious to erythroid progenitor cells. To assess the importance of the EC catalytic subunits Dis3 and Exosc10 in this dynamic process, we asked if these subunits function non-redundantly to control erythropoiesis. Dis3 or Exosc10 depletion in primary murine hematopoietic progenitor cells reduced erythroid progenitors and their progeny, while sparing myeloid cells. Dis3 loss severely compromised erythroid progenitor and erythroblast survival, rendered erythroblasts hypersensitive to apoptosis-inducing stimuli and induced γ-H2AX, indicative of DNA double-stranded breaks. Dis3 loss-of-function phenotypes were more severe than those caused by Exosc10 depletion. We innovated a genetic rescue system to compare human Dis3 with multiple myeloma-associated Dis3 mutants S447R and R750K, and only wild type Dis3 was competent to rescue progenitors. Thus, Dis3 establishes a disease mutation-sensitive, cell type-specific survival mechanism to enable a differentiation program.
Hematopoietic development requires the transcription factor GATA-2, and GATA-2 mutations cause diverse pathologies, including leukemia. GATA-2-regulated enhancers increase Gata2 expression in ...hematopoietic stem/progenitor cells and control hematopoiesis. The +9.5-kb enhancer activates transcription in endothelium and hematopoietic stem cells (HSCs), and its deletion abrogates HSC generation. The −77-kb enhancer activates transcription in myeloid progenitors, and its deletion impairs differentiation. Since +9.5−/− embryos are HSC deficient, it was unclear whether the +9.5 functions in progenitors or if GATA-2 expression in progenitors solely requires −77. We further dissected the mechanisms using −77;+9.5 compound heterozygous (CH) mice. The embryonic lethal CH mutation depleted megakaryocyte-erythrocyte progenitors (MEPs). While the +9.5 suffices for HSC generation, the −77 and +9.5 must reside on one allele to induce MEPs. The −77 generated burst-forming unit-erythroid through the induction of GATA-1 and other GATA-2 targets. The enhancer circuits controlled signaling pathways that orchestrate a GATA factor-dependent blood development program.
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•Gata2 enhancers are required to generate megakaryocyte-erythocyte progenitors•Gata2 −77 enhancer is required to generate burst-forming unit-erythroid•GATA-2 target gene ensemble confers vital developmental signaling•Enhancer integration establishes the hematopoietic hierarchy
Mutations of GATA2 and its enhancers cause immunodeficiency, myelodysplastic syndrome, and leukemia. Mehta et al. report that enhancers linked to these pathologies function collectively to generate a vital blood precursor, while a single enhancer generates a distinct blood precursor.
Targeting the genome with sequence-specific DNA-binding molecules is a major goal at the interface of chemistry, biology, and precision medicine. Polyamides, composed of N-methylpyrrole and ...N-methylimidazole monomers, are a class of synthetic molecules that can be rationally designed to “read” specific DNA sequences. However, the impact of different chromatin states on polyamide binding in live cells remains an unresolved question that impedes their deployment in vivo. Here, we use cross-linking of small molecules to isolate chromatin coupled to sequencing to map the binding of two bioactive and structurally distinct polyamides to genomes directly within live H1 human embryonic stem cells. This genome-wide view from live cells reveals that polyamide-based synthetic genome readers bind cognate sites that span a range of binding affinities. Polyamides can access cognate sites within repressive heterochromatin. The occupancy patterns suggest that polyamides could be harnessed to target loci within regions of the genome that are inaccessible to other DNA-targeting molecules.
In this study, degradation of a pharmaceutical drug, Phenazone (PNZ) has been carried out via heterogeneous photocatalysis, photo-Fenton and in-situ dual process (photocatalysis + photo-Fenton) in ...suspension and fixed-mode under artificial UV-A as well as under natural solar radiations. Waste material such as foundry sand (FS) was exploited as a supplement for iron in case of photo-Fenton reaction. The distinct processes including photocatalysis and photo-Fenton were found to be competent for the degradation of PNZ as both processes revealed an almost 90–95% removal of PNZ after 180 min of UV irradiations. The degradation was improved to a great extent with remarkable reduction in treatment time of PNZ to almost 105 min when these two individual processes were combined together within the same unit. An almost 14% synergy of dual process over distinct processes was obtained. For fixed-bed studies, TiO2 immobilized hollow circular composite disc already containing FS was utilized which yielded an almost 96% reduction in the concentration of PNZ after 4 h of solar irradiations. The disc was recycled 10 times and its stability and activity was confirmed through XRD, SEM/EDS, and DRS. The mineralization of PNZ was confirmed through significant reduction in COD and generation of anions during the treatment process. The transformation products were examined through GC-MS analysis. The novel technique of in-situ dual process especially in fixed-mode visualized in this study by employing renewable energy and durable catalyst can represent a viable solution to various industries for the treatment of wastewater comprising of bio-recalcitrant pollutants.
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•An economically viable process has been studied for the treatment of wastewater.•Waste foundry sand was used as an iron source.•Synergistic results over discrete processes were obtained through dual process.•Treatment time of phenazone was significantly reduced via dual process.•Fe-TiO2 composite disc was recycled 10 times.
A novel concept of integrated process by coupling photocatalysis and photo-Fenton especially in fixed mode has been presented in the current study for the removal of recalcitrant pharmaceuticals like ...cephalexin (CEX) from aqueous solution in reduced treatment time. Waste materials like foundry sand (FS) was used as a substitute for iron along with TiO
2
. The parametric optimization was carried out in slurry mode using Box–Behnken design model (BBD) and response surface methodology. For fixed-bed studies, support materials of varying shapes (hollow circular disk, rectangular slabs, spherical beads) were prepared using clay in conjunction with FS for TiO
2
immobilization. Different supports were compared on the basis of degradation efficiency, exposed surface area of catalyst as well as their recyclability capacity for the degradation of CEX. Iron was leaching by default from the supports during the degradation process which contributed simultaneously to photo-Fenton process along with photocatalysis. Spherical beads with 0.0265 m
2
exposed surface area of catalyst and better recyclability efficiency (10 cycles) yielded best degradation efficiency (80%) of CEX after 240 min of treatment time. The presence of iron along with TiO
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on the surface of beads was confirmed through TGA, SEM/EDS, XRD, DRS and FTIR. The mineralization of CEX was validated through quantification of nitrite, nitrate and sulfate ions along with reduction in COD. A tentative pathway for the degradation of CEX was also proposed based on the identification of intermediates through GC–MS analysis.
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