Spatiotemporal immune atlas of a clinical-grade gene-edited pig-to-human kidney xenotransplant.

Pig-to-human xenotransplantation is rapidly approaching the clinical arena; however, it is unclear which immunomodulatory regimens will effectively control human immune responses to pig xenografts. Here, we transplant a gene-edited pig kidney into a brain-dead human recipient on pharmacologic immunosuppression and study the human immune response to the xenograft using spatial transcriptomics and single-cell RNA sequencing. Human immune cells are uncommon in the porcine kidney cortex early after xenotransplantation and consist of primarily myeloid cells. Both the porcine resident macrophages and human infiltrating macrophages express genes consistent with an alternatively activated, anti-inflammatory phenotype. No significant infiltration of human B or T cells into the porcine kidney xenograft is detectable. Altogether, these findings provide proof of concept that conventional pharmacologic immunosuppression may be able to restrict infiltration of human immune cells into the xenograft early after compatible pig-to-human kidney xenotransplantation.

ATAD2 is a driver and a therapeutic target in ovarian cancer that functions by upregulating CENPE.

Ovarian cancer is a complex disease associated with multiple genetic and epigenetic alterations. The emergence of treatment resistance in most patients causes ovarian cancer to become incurable, and novel therapies remain necessary. We identified epigenetic regulator ATPase family AAA domain-containing 2 (ATAD2) is overexpressed in ovarian cancer and is associated with increased incidences of metastasis and recurrence. Genetic knockdown of ATAD2 or its pharmacological inhibition via ATAD2 inhibitor BAY-850 suppressed ovarian cancer growth and metastasis in both in vitro and in vivo models. Transcriptome-wide mRNA expression profiling of ovarian cancer cells treated with BAY-850 revealed that ATAD2 inhibition predominantly alters the expression of centromere regulatory genes, particularly centromere protein E (CENPE). In ovarian cancer cells, changes in CENPE expression following ATAD2 inhibition resulted in cell-cycle arrest and apoptosis induction, which led to the suppression of ovarian cancer growth. Pharmacological CENPE inhibition phenotypically recapitulated the cellular changes induced by ATAD2 inhibition, and combined pharmacological inhibition of both ATAD2 and CENPE inhibited ovarian cancer cell growth more potently than inhibition of either alone. Thus, our study identified ATAD2 as regulators of ovarian cancer growth and metastasis that can be targeted either alone or in combination with CENPE inhibitors for effective ovarian cancer therapy.

Spatiotemporal immune atlas of the first clinical-grade, gene-edited pig-to-human kidney xenotransplant.

Pig-to-human xenotransplantation is rapidly approaching the clinical arena; however, it is unclear which immunomodulatory regimens will effectively control human immune responses to pig xenografts. We transplanted a gene-edited pig kidney into a brain-dead human recipient on pharmacologic immunosuppression and studied the human immune response to the xenograft using spatial transcriptomics and single-cell RNA sequencing. Human immune cells were uncommon in the porcine kidney cortex early after xenotransplantation and consisted of primarily myeloid cells. Both the porcine resident macrophages and human infiltrating macrophages expressed genes consistent with an alternatively activated, anti-inflammatory phenotype. No significant infiltration of human B or T cells into the porcine kidney xenograft was detected. Altogether, these findings provide proof of concept that conventional pharmacologic immunosuppression is sufficient to restrict infiltration of human immune cells into the xenograft early after compatible pig-to-human kidney xenotransplantation.

IL-4 receptor blockade is a global repressor of naïve B cell development and responses in a dupilumab-treated patient.

Here, we report a case of atopic dermatitis (AD) in a patient who received biweekly doses of dupilumab, an antibody against the IL-4 receptor α chain (IL-4Rα). Single cell RNA-sequencing showed that naïve B cells expressed the highest levels of IL4R compared to other B cell subpopulations. Compared to controls, the dupilumab-treated patient exhibited diminished percentages of IL4R+IGHD+ naïve B cells and down-regulation of IL4R, FCER2 (CD23), and IGHD. Dupilumab treatment resulted in upregulation of genes associated with apoptosis and inhibition of B cell receptor signaling and down-regulation of class-switch and memory B cell development genes. The dupilumab-treated patient exhibited a rapid decline in COVID-19 anti-spike and anti-receptor binding domain antibodies between 4 and 8 and 11 months post COVID-19 vaccination. Our data suggest that intact and persistent IL-4 signaling is necessary for maintaining robust survival and development of naïve B cells, and maintaining a long term vaccine response.

Methylation of dual-specificity phosphatase 4 controls cell differentiation.

Mitogen-activated protein kinases (MAPKs) are inactivated by dual-specificity phosphatases (DUSPs), the activities of which are tightly regulated during cell differentiation. Using knockdown screening and single-cell transcriptional analysis, we demonstrate that DUSP4 is the phosphatase that specifically inactivates p38 kinase to promote megakaryocyte (Mk) differentiation. Mechanistically, PRMT1-mediated methylation of DUSP4 triggers its ubiquitinylation by an E3 ligase HUWE1. Interestingly, the mechanistic axis of the DUSP4 degradation and p38 activation is also associated with a transcriptional signature of immune activation in Mk cells. In the context of thrombocytopenia observed in myelodysplastic syndrome (MDS), we demonstrate that high levels of p38 MAPK and PRMT1 are associated with low platelet counts and adverse prognosis, while pharmacological inhibition of p38 MAPK or PRMT1 stimulates megakaryopoiesis. These findings provide mechanistic insights into the role of the PRMT1-DUSP4-p38 axis on Mk differentiation and present a strategy for treatment of thrombocytopenia associated with MDS.

Exogenous sickle erythrocytes combined with vascular disruption trigger disseminated tumor vaso-occlusion and lung tumor regression.

Hypoxic tumor niches are chief causes of treatment resistance and tumor recurrence. Sickle erythrocytes' (SSRBCs') intrinsic oxygen-sensing functionality empowers them to access such hypoxic niches wherein they form microaggregates that induce focal vessel closure. In search of measures to augment the scale of SSRBC-mediated tumor vaso-occlusion, we turned to the vascular disrupting agent, combretastatin A-4 (CA-4). CA-4 induces selective tumor endothelial injury, blood stasis, and hypoxia but fails to eliminate peripheral tumor foci. In this article, we show that introducing deoxygenated SSRBCs into tumor microvessels treated with CA-4 and sublethal radiation (SR) produces a massive surge of tumor vaso-occlusion and broadly propagated tumor infarctions that engulfs treatment-resistant hypoxic niches and eradicates established lung tumors. Tumor regression was histologically corroborated by significant treatment effect. Treated tumors displayed disseminated microvessels occluded by tightly packed SSRBCs along with widely distributed pimidazole-positive hypoxic tumor cells. Humanized HbS-knockin mice (SSKI) but not HbA-knockin mice (AAKI) showed a similar treatment response underscoring SSRBCs as the paramount tumoricidal effectors. Thus, CA-4-SR-remodeled tumor vessels license SSRBCs to produce an unprecedented surge of tumor vaso-occlusion and infarction that envelops treatment-resistant tumor niches resulting in complete tumor regression. Strategically deployed, these innovative tools constitute a major conceptual advance with compelling translational potential.

Hemoglobin ß93 Cysteine Is Not Required for Export of Nitric Oxide Bioactivity From the Red Blood Cell.

BACKGROUND: Nitrosation of a conserved cysteine residue at position 93 in the hemoglobin ß chain (ß93C) to form S-nitroso (SNO) hemoglobin (Hb) is claimed to be essential for export of nitric oxide (NO) bioactivity by the red blood cell (RBC) to mediate hypoxic vasodilation and cardioprotection. METHODS: To test this hypothesis, we used RBCs from mice in which the ß93 cysteine had been replaced with alanine (ß93A) in a number of ex vivo and in vivo models suitable for studying export of NO bioactivity. RESULTS: In an ex vivo model of cardiac ischemia/reperfusion injury, perfusion of a mouse heart with control RBCs (ß93C) pretreated with an arginase inhibitor to facilitate export of RBC NO bioactivity improved cardiac recovery after ischemia/reperfusion injury, and the response was similar with ß93A RBCs. Next, when human platelets were coincubated with RBCs and then deoxygenated in the presence of nitrite, export of NO bioactivity was detected as inhibition of ADP-induced platelet activation. This effect was the same in ß93C and ß93A RBCs. Moreover, vascular reactivity was tested in rodent aortas in the presence of RBCs pretreated with S-nitrosocysteine or with hemolysates or purified Hb treated with authentic NO to form nitrosyl(FeII)-Hb, the proposed precursor of SNO-Hb. SNO-RBCs or NO-treated Hb induced vasorelaxation, with no differences between ß93C and ß93A RBCs. Finally, hypoxic microvascular vasodilation was studied in vivo with a murine dorsal skin-fold window model. Exposure to acute systemic hypoxia caused vasodilatation, and the response was similar in ß93C and ß93A mice. CONCLUSIONS: RBCs clearly have the fascinating ability to export NO bioactivity, but this occurs independently of SNO formation at the ß93 cysteine of Hb.

Defining the epigenetic status of blood cells using a cyanine-based fluorescent probe for PRMT1.

Dynamic regulation of histone modification enzymes such as PRMT1 (protein arginine methyltransferase 1) determines the ordered epigenetic transitions in hematopoiesis. Sorting cells according to the expression levels of histone modification enzymes may further define subpopulations in hematopoietic lineages with unique differentiation potentials that are presently defined by surface markers. We discovered a vital near infrared dye, E84, that fluoresces brightly following binding to PRMT1 and excitation with a red laser. The staining intensity as measured by flow cytometry is correlated with the PRMT1 expression level. Importantly, E84 staining has no apparent negative effect on the proliferation of the labeled cells. Given that long-term hematopoietic stem cells (LT-HSCs) produce low levels of PRMT1, we used E84 to sort LT-HSCs from mouse bone marrow. We found that SLAM (the signalling lymphocyte activation molecule family) marker-positive LT-HSCs were enriched in the E84low cell fraction. We then performed bone marrow transplantations with E84high or E84low Lin-Sca1+Kit+ (LSK) cells and showed that whole blood cell lineages were successfully reconstituted 16 weeks after transplanting 200 E84low LSK cells. Thus, E84 is a useful new tool to probe the role of PRMT1 in hematopoiesis and leukemogenesis. Developing E84 and other small molecules to label histone modification enzymes provides a convenient approach without modifying gene loci to study the interaction between hematopoietic stem/progenitor cell epigenetic status and differentiation state.

Bone Marrow Transplantation after Nonmyeloablative Treosulfan Conditioning Is Curative in a Murine Model of Sickle Cell Disease.

Allogeneic hematopoietic stem cell transplantation (HSCT) can be curative for patients with sickle cell disease (SCD). However, morbidity associated with myeloablative conditioning and graft-versus-host disease has limited its utility. To this end, autologous HSCT for SCD using lentiviral gene-modified bone marrow (BM) or peripheral blood stem cells has been undertaken, although toxicities of fully ablative conditioning with busulfan and incomplete engraftment have been encountered. Treosulfan, a busulfan analog with a low extramedullary toxicity profile, has been used successfully as part of a myeloablative conditioning regimen in the allogeneic setting in SCD. To further minimize toxicity of conditioning, noncytotoxic monoclonal antibodies that clear stem cells from the marrow niche, such as anti-c-Kit (ACK2), have been considered. Using a murine model of SCD, we sought to determine whether nonmyeloablative conditioning followed by transplantation with syngeneic BM cells could ameliorate the disease phenotype. Treosulfan and ACK2, in a dose-dependent manner, decreased BM cellularity and induced cytopenia in SCD mice. Conditioning with treosulfan alone at nonmyeloablative dosing (3.6 g/kg), followed by transplantation with syngeneic BM donor cells, permitted long-term mixed-donor chimerism. Level of chimerism correlated with improvement in hematologic parameters, normalization of urine osmolality, and improvement in liver and spleen pathology. Addition of ACK2 to treosulfan conditioning did not enhance engraftment. Our data suggests that pretransplant conditioning with treosulfan alone may allow sufficient erythroid engraftment to reverse manifestations of SCD, with clinical application as a preparative regimen in SCD patients undergoing gene-modified autologous HSCT.

Sickle cells produce functional immune modulators and cytotoxics.

Sickle erythrocytes' (SSRBCs) unique physical adaptation to hypoxic conditions renders them able to home to hypoxic tumor niches in vivo, shut down tumor blood flow and induce tumoricidal responses. SSRBCs are also useful vehicles for transport of encapsulated drugs and oncolytic virus into hypoxic tumors with enhanced anti-tumor effects. In search of additional modes for arming sickle cells with cytotoxics, we turned to a lentiviral ß-globin vector with optimized Locus Control Region/ß-globin coding region/promoter/enhancers. We partially replaced the ß-globin coding region of this vector with genes encoding T cell cytolytics, perforin and granzyme or immune modulating superantigens SEG and SEI. These modified vectors efficiently transduced Sca+ ckit- Lin- hematopoietic stem cells (HSCs) from humanized sickle cell knockin mice. Irradiated mice reconstituted with these HSCs displayed robust expression of transgenic RNAs and proteins in host sickle cells that was sustained for more than 10 months. SSRBCs from reconstituted mice harboring SEG/SEI transgenes induced robust proliferation and a prototypical superantigen-induced cytokine reaction when exposed to human CD4+/CD8+ cells. The ß-globin lentiviral vector therefore produces a high level of functional, erythroid-specific immune modulators and cytotoxics that circulate without toxicity. Coupled with their unique ability to target and occlude hypoxic tumor vessels these armed SSRBCs constitute a potentially useful tool for treatment of solid tumors.

Induced Pluripotent Stem Cell-Derived Endothelial Cells Overexpressing Interleukin-8 Receptors A/B and/or C-C Chemokine Receptors 2/5 Inhibit Vascular Injury Response.

Recruitment of neutrophils and monocytes/macrophages to the site of vascular injury is mediated by binding of chemoattractants to interleukin (IL) 8 receptors RA and RB (IL8RA/B) C-C chemokine receptors (CCR) 2 and 5 expressed on neutrophil and monocyte/macrophage membranes. Endothelial cells (ECs) derived from rat-induced pluripotent stem cells (RiPS) were transduced with adenovirus containing cDNA of IL8RA/B and/or CCR2/5. We hypothesized that RiPS-ECs overexpressing IL8RA/B (RiPS-IL8RA/B-ECs), CCR2/5 (RiPS-CCR2/5-ECs), or both receptors (RiPS-IL8RA/B+CCR2/5-ECs) will inhibit inflammatory responses and neointima formation in balloon-injured rat carotid artery. Twelve-week-old male Sprague-Dawley rats underwent balloon injury of the right carotid artery and intravenous infusion of (a) saline vehicle, (b) control RiPS-Null-ECs (ECs transduced with empty virus), (c) RiPS-IL8RA/B-ECs, (d) RiPS-CCR2/5-ECs, or (e) RiPS-IL8RA/B+CCR2/5-ECs. Inflammatory mediator expression and leukocyte infiltration were measured in injured and uninjured arteries at 24 hours postinjury by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, respectively. Neointima formation was assessed at 14 days postinjury. RiPS-ECs expressing the IL8RA/B or CCR2/5 homing device targeted the injured arteries and decreased injury-induced inflammatory cytokine expression, neutrophil/macrophage infiltration, and neointima formation. Transfused RiPS-ECs overexpressing IL8RA/B and/or CCR2/5 prevented inflammatory responses and neointima formation after vascular injury. Targeted delivery of iPS-ECs with a homing device to inflammatory mediators in injured arteries provides a novel strategy for the treatment of cardiovascular diseases. Stem Cells Translational Medicine 2017;6:1168-1177.

Novel HDAd/EBV Reprogramming Vector and Highly Efficient Ad/CRISPR-Cas Sickle Cell Disease Gene Correction.

CRISPR/Cas enhanced correction of the sickle cell disease (SCD) genetic defect in patient-specific induced Pluripotent Stem Cells (iPSCs) provides a potential gene therapy for this debilitating disease. An advantage of this approach is that corrected iPSCs that are free of off-target modifications can be identified before differentiating the cells into hematopoietic progenitors for transplantation. In order for this approach to be practical, iPSC generation must be rapid and efficient. Therefore, we developed a novel helper-dependent adenovirus/Epstein-Barr virus (HDAd/EBV) hybrid reprogramming vector, rCLAE-R6, that delivers six reprogramming factors episomally. HDAd/EBV transduction of keratinocytes from SCD patients resulted in footprint-free iPSCs with high efficiency. Subsequently, the sickle mutation was corrected by delivering CRISPR/Cas9 with adenovirus followed by nucleoporation with a 70 nt single-stranded oligodeoxynucleotide (ssODN) correction template. Correction efficiencies of up to 67.9% (ß(A)/[ß(S)+ß(A)]) were obtained. Whole-genome sequencing (WGS) of corrected iPSC lines demonstrated no CRISPR/Cas modifications in 1467 potential off-target sites and no modifications in tumor suppressor genes or other genes associated with pathologies. These results demonstrate that adenoviral delivery of reprogramming factors and CRISPR/Cas provides a rapid and efficient method of deriving gene-corrected, patient-specific iPSCs for therapeutic applications.

Peroxiredoxin-2 recycling is inhibited during erythrocyte storage.

AIMS: Transfusion with stored red blood cells (RBCs) is associated with increased morbidity and mortality. Peroxiredoxin-2 (Prx-2) is a primary RBC antioxidant that limits hydrogen peroxide (H2O2)-mediated toxicity. Whether Prx-2 activity is altered during RBC storage is not known. RESULTS: Basal and H2O2-induced Prx-2 activity was measured in RBCs (stored for 7-35 days). Basal Prx-2 thiol oxidation increased with RBC age, whereas H2O2-dependent formation of dimeric Prx-2 was similar. However, reduction of Prx-2 dimers to monomers became progressively slower with RBC storage, which was associated with increased H2O2-induced hemolysis. Surprisingly, no change in the NADPH-dependent thioredoxin (Trx)/Trx-reductase system, which recycles dimeric Prx-2, was observed in stored RBCs. Using mouse RBCs expressing human wild type (ß93Cys) or hemoglobin (Hb) in which the conserved ß93Cys residue is replaced by Ala (ß93Ala), a role for this thiol in modulating Prx-2 reduction was demonstrated. Specifically, Prx-2 recycling was blunted in ß93Ala RBC, which was reversed by carbon monoxide-treatment, suggesting that heme autoxidation-derived H2O2 maintains Prx-2 in the oxidized form in these cells. Moreover, assessment of the oxidative state of the ß93Cys in RBCs during storage showed that while it remained reduced on intraerythrocytic Hb in stored RBC, it was oxidized to dehydroalanine on hemolyzed or extracellular Hb. INNOVATION: A novel mechanism for regulated Prx-2 activity in RBC via the ß93Cys residue is suggested. CONCLUSION: These data highlight the potential for slower Prx-2 recycling and ß93Cys oxidation in modulating storage-dependent damage of RBCs and in mediating post-transfusion toxicity.

Role of the b93cys, ATP and adenosine in red cell dependent hypoxic vasorelaxation.

Two of the proposed mechanisms by which red blood cells (RBC) mediate hypoxic vasorelaxation by coupling hemoglobin deoxygenation to the activation of nitric oxide signaling involve ATP-release from RBC and S-nitrosohemoglobin (b93C(SNO)Hb) dependent bioactivity. However, different studies have reached opposite conclusions regarding the aforementioned mechanisms. Using isolated vessels, hypoxic vasorelaxation induced by human, C57BL/6 or mouse RBC which exclusively express either native human hemoglobin (HbC93) or human hemoglobin in which the conserved b93cys was replaced with Ala (HbC93A) were compared. All RBCs stimulated hypoxic vasodilation to similar extents suggesting the b93cys is not required for this RBC-mediated function. Hypoxic vasorelaxation was inhibited by co-incubation of ATP-pathway blockers including L-NAME (eNOS inhibitor) and Apyrase. Moreover, we tested if modulation of adenosine-dependent signaling affected RBC-dependent vasorelaxation using pan- or subtype specific adenosine receptor blockers, or adenosine deaminase (ADA). Interestingly, ADA and adenosine A2 receptor blockade, but not A1 receptor blockade, inhibited HbC93, HbC93A dependent hypoxic vasorelaxation. Equivalent results were obtained with human RBC. These data suggest that using isolated vessels, RBC do not require the presence of the b93cys to elicit hypoxic vasorelaxation and mediate this response via ATP- and a novel adenosine-dependent mechanism.

Antioxidant functions for the hemoglobin ß93 cysteine residue in erythrocytes and in the vascular compartment in vivo.

The ß93 cysteine (ß93Cys) residue of hemoglobin is conserved in vertebrates but its function in the red blood cell (RBC) remains unclear. Because this residue is present at concentrations more than 2 orders of magnitude higher than enzymatic components of the RBC antioxidant network, a role in the scavenging of reactive species was hypothesized. Initial studies utilizing mice that express human hemoglobin with either Cys (B93C) or Ala (B93A) at the ß93 position demonstrated that loss of the ß93Cys did not affect activities nor expression of established components of the RBC antioxidant network (catalase, superoxide dismutase, peroxiredoxin-2, glutathione peroxidase, GSH:GSSG ratios). Interestingly, exogenous addition to RBCs of reactive species that are involved in vascular inflammation demonstrated a role for the ß93Cys in hydrogen peroxide and chloramine consumption. To simulate oxidative stress and inflammation in vivo, mice were challenged with lipopolysaccharide (LPS). Notably, LPS induced a greater degree of hypotension and lung injury in B93A versus B93C mice, which was associated with greater formation of RBC reactive species and accumulation of DMPO-reactive epitopes in the lung. These data suggest that the ß93Cys is an important effector within the RBC antioxidant network, contributing to the modulation of tissue injury during vascular inflammation.

Background mutations in parental cells account for most of the genetic heterogeneity of induced pluripotent stem cells.

To assess the genetic consequences of induced pluripotent stem cell (iPSC) reprogramming, we sequenced the genomes of ten murine iPSC clones derived from three independent reprogramming experiments, and compared them to their parental cell genomes. We detected hundreds of single nucleotide variants (SNVs) in every clone, with an average of 11 in coding regions. In two experiments, all SNVs were unique for each clone and did not cluster in pathways, but in the third, all four iPSC clones contained 157 shared genetic variants, which could also be detected in rare cells (<1 in 500) within the parental MEF pool. These data suggest that most of the genetic variation in iPSC clones is not caused by reprogramming per se, but is rather a consequence of cloning individual cells, which "captures" their mutational history. These findings have implications for the development and therapeutic use of cells that are reprogrammed by any method.

Heme-regulated eIF2α kinase activated Atf4 signaling pathway in oxidative stress and erythropoiesis.

Heme-regulated eIF2α kinase (Hri) is necessary for balanced synthesis of heme and globin. In addition, Hri deficiency exacerbates the phenotypic severity of ß-thalassemia intermedia in mice. Activation of Hri during heme deficiency and in ß-thalassemia increases eIF2α phosphorylation and inhibits globin translation. Under endoplasmic reticulum stress and nutrient starvation, eIF2α phosphorylation also induces the Atf4 signaling pathway to mitigate stress. Although the function of Hri in regulating globin translation is well established, its role in Atf4 signaling in erythroid precursors is not known. Here, we report the role of the Hri-activated Atf4 signaling pathway in reducing oxidative stress and in promoting erythroid differentiation during erythropoiesis. On acute oxidative stress, Hri(-/-) erythroblasts suffered from increased levels of reactive oxygen species (ROS) and apoptosis. During chronic iron deficiency in vivo, Hri is necessary both to reduce oxidative stress and to promote erythroid differentiation. Hri(-/-) mice developed ineffective erythropoiesis during iron deficiency with inhibition of differentiation at the basophilic erythroblast stage. This inhibition is recapitulated during ex vivo differentiation of Hri(-/-) fetal liver erythroid progenitors. Importantly, the Hri-eIF2αP-Atf4 pathway was activated and required for erythroid differentiation. We further demonstrate the potential of modulating Hri-eIF2αP-Atf4 signaling with chemical compounds as pharmaceutical therapies for ß-thalassemia.

PRC2 complexes with JARID2, MTF2, and esPRC2p48 in ES cells to modulate ES cell pluripotency and somatic cell reprogramming.

Polycomb repressive complex two (PRC2) has been implicated in embryonic stem (ES) cell pluripotency; however, the mechanistic roles of this complex are unclear. It was assumed that ES cells contain PRC2 with the same subunit composition as that identified in HeLa cells and Drosophila embryos. Here, we report that PRC2 in mouse ES cells contains at least three additional subunits: JARID2, MTF2, and a novel protein denoted esPRC2p48. JARID2, MTF2, and esPRC2p48 are highly expressed in mouse ES cells compared to differentiated cells. Importantly, knockdowns of JARID2, MTF2, or esPRC2p48 alter the level of PRC2-mediated H3K27 methylation and result in the expression of differentiation-associated genes in ES cells. Interestingly, expression of JARID2, MTF2, and esPRC2p48 together, but not individually, enhances Oct4/Sox2/Klf4-mediated reprogramming of mouse embryonic fibroblasts (MEFs) into induced pluripotent stem cells, whereas knockdown or knockout of JARID2, MTF2, or esPRC2p48 significantly inhibits reprogramming. JARID2, MTF2, and esPRC2p48 modulate H3K27 methylation and facilitate repression of lineage-associated gene expression when transduced into MEFs, and synergistically stimulate the histone methyltransferase activity of PRC2 in vitro. Therefore, these studies identify JARID2, MTF2, and esPRC2p48 as important regulatory subunits of PRC2 in ES cells and reveal critical functions of these subunits in modulating PRC2's activity and gene expression both in ES cells and during somatic cell reprogramming.

Negative regulation of IRF7 activation by activating transcription factor 4 suggests a cross-regulation between the IFN responses and the cellular integrated stress responses.

Cells react to viral infection by exhibiting IFN-based innate immune responses and integrated stress responses, but little is known about the interrelationships between the two. In this study, we report a linkage between these two host-protective cellular mechanisms. We found that IFN regulatory factor (IRF)7, the master regulator of type I IFN gene expression, interacts with activating transcription factor (ATF)4, a key component of the integrated stress responses whose translation is induced by viral infection and various stresses. We have demonstrated that IRF7 upregulates ATF4 activity and expression, whereas ATF4 in return inhibits IRF7 activation, suggesting a cross-regulation between the IFN response and the cellular integrated stress response that controls host innate immune defense against viral infection.

KLF1 regulates BCL11A expression and gamma- to beta-globin gene switching.

We show that knockdown of KLF1 in human and mouse adult erythroid progenitors markedly reduces BCL11A levels and increases human gamma-globin/beta-globin expression ratios. These results suggest that KLF1 controls globin gene switching by directly activating beta-globin and indirectly repressing gamma-globin gene expression. Controlled knockdown of KLF1 in adult erythroid progenitors may provide a method to activate fetal hemoglobin expression in individuals with beta-thalassemia or sickle cell disease.