Blood

Background Thalassemia is one of the most common monogenic disorders worldwide, current screening strategies combining hematological testing with molecular assays still carry a risk of missed diagnoses and undesirable efficiency, particularly for complex structural variants and rare mutations. Methods In this prospective double-blind, multicenter cohort study of 3,842 participants (3,362 pregnant women and 480 male partners), we conducted a head-to-head comparison to systematically evaluate the incremental clinical value and detection performance of single-molecule nanopore sequencing in thalassemia (SMITH) against conventional hematological testing and next-generation sequencing (NGS). Findings The overall concordance rate between NGS and SMITH was 98.6% (3789/3842). The discrepant cases (n=53) were directly attributed to the superior detection capabilities of SMITH, which successfully identified complex structural rearrangements-including 45 -globin gene triplications and four HK alleles-that were missed by NGS. Furthermore, SMITH accurately detected four rare variants (c.134_135insT/, c.-22(C>T)/, {beta}N/{beta}c.316-290delinsAGGGCAATAATTT and {beta}3.5 kb deletion/{beta}N ) and resolved ten trans and three cis configurations within the globin gene allele. Clinically, these technical advantages translated to a 9.3% (5/54) increase in the detection rate of high-risk prenatal couples, effectively preventing one birth affected by moderate-to-severe thalassemia. Additionally, SMITH corrected a diagnostic discrepancy in one case (HK vs. -3.7), sparing the couple from an unnecessary invasive procedure. Interpretation Our findings demonstrate that SMITH provides a powerful platform for resolving globin gene rearrangements, detecting rare variants, and enabling direct haplotype phasing. By effectively eliminating diagnostic blind spots, SMITH is expected to become an optimal method for thalassemia prevention programs. Funding This study was supported by Chinese National Natural Science Foundation Projects 81760037 and 82271894.

The genetic risk factors of immune cytopenias are unclear. Immune cytopenias have been reported in various genetic contexts: 1) inherited error of immunity genes, mainly due to rare germline variants, 2) systemic lupus erythematosus, associated with common germline variants, 3) hematological malignancies, and 4) clonal hematopoiesis, the latter two due to somatic variants. However, the respective contribution and interaction of these variants remain to be investigated. Here, we used two large biobanks with whole genome sequencing data to systematically investigate the genetic contribution to immune cytopenia. We found that the four types of genetic variants independently contribute to immune cytopenia risk. We notably found that carriers of variants in some autosomal recessive genes of inherited error of immunity had an increased risk of immune cytopenia. Additionally, common variant-mediated risk of systemic lupus erythematosus also increased the risk of immune cytopenia. Overall, a third to a half of patients with immune cytopenia carried at least one of the four genetic risk variants investigated. Combining the four variants allowed stratifying the risk of immune cytopenia in both general and high-risk population. In general population, the 10-year incidence of immune cytopenia in the lowest and highest risk groups was 0.08% and 1.5%, respectively. In sum, this work identified that different genetic risk factors can lead to immune cytopenia. A large proportion of individuals with immune cytopenia carried an underlying genetic risk factor. Finally, combining these genetic risk factors enabled risk stratification.

Background Monoclonal gammopathy of thrombotic significance (MGTS) is a recently described chronic prothrombotic condition characterized by monoclonal anti-PF4 antibodies that are detected above the polyclonal antibody background in patient sera (i.e. present as monoclonal gammopathy of undetermined significance, MGUS). Due to conflicting data in the published literature on antibody clonality in heparin-induced thrombocytopenia (HIT), we evaluated clonality and abundance of anti-PF4 antibodies in HIT, including investigating whether an MGUS, if present in HIT, represents the causative anti-PF4 antibody. Methods Blood samples from 15 patients with HIT were subject to Platelet Factor 4-dependent antigen-based and functional tests. The unmanipulated serum antibody repertoire and isolated anti-PF4 antibodies were subjected to mass spectrometric evaluation. Results Two of the 15 HIT patients had an IgG MGUS. Notably, anti-PF4 antibodies were not synonymous with the MGUS antibody in either of the two patients. Eight of the 15 patients demonstrated monoclonal anti-PF4 antibodies, however, none of the anti-PF4 antibodies were detectable as an MGUS upon evaluation of the entire serum antibody repertoire, reflecting their low abundance. In the seven patients with multiple anti-PF4 antibodies, non-monoclonality was confirmed by analysis of deglycosylated antibody heavy chains. Conclusions Anti-PF4 HIT antibodies are monoclonal in approximately 50% of HIT patients, however, antibody abundance is low such that they are not detectable over the polyclonal IgG background (i.e. are MGUS-negative), differentiating HIT from MGTS. This observation helps explain the transient nature of HIT relative to the persistent prothrombotic state seen in MGTS.

Clinical evidence demonstrates that ex vivo gene therapy and genome engineering of hematopoietic stem and progenitor cells (HSPCs) could represent one-time cures. However, while genome editing itself has become increasingly efficient and precise, the toxic conditioning required for hematopoietic stem cell transplantation remains a major barrier to broad clinical implementation of these otherwise curative therapies. In particular, the use of busulfan for myeloablative conditioning constitutes a major safety concern. While preclinical studies established CD117 as a promising target for antigen-specific therapy, clinical translation faced setbacks balancing efficacy and safety. To overcome current limitations, we generated a new CD117-blocking monoclonal antibody (CIM058) and demonstrate its potency to block wild-type HSPCs. To enable long-term blockade of host HSPCs even after transplantation, we used prime editing to engineer CIM058-resistant human CD34+ HSPCs. When combined, CIM058 and the epitope engineered CD34+ HSPCs ameliorated disease phenotype in a {beta}-thalassemia model. Our results suggest that this approach may overcome the reliance on busulfan or other myeloablative conditioning regimens with their associated morbidities, and by enabling toxin-free conditioning and in vivo selection of edited cells, may facilitate clinical implementation of these highly valuable genetic therapies.

LZTR1 negatively regulates RAS family proteins via proteasomal degradation. Germline loss-of-function variants cause Noonan syndrome, with emerging evidence implicating LZTR1 in predisposition to childhood acute lymphoblastic leukemia (ALL), though its role in hematopoiesis remains poorly defined. Screening 1,587 children with ALL identified LZTR1 variants in 44 patients (2.8%). Germline variants were detected in 32 patients (2.0%), a frequency comparable to that observed in the general population (1.75%; 1,925/110,017; p=0.50). Somatic LZTR1 alterations were identified in 22 patients (1.4%) and were predominantly bi-allelic, arising through either a germline-plus-somatic or dual somatic configuration. They persisted at relapse. Despite enrichment in favorable-risk subtypes (ETV6::RUNX1, high-hyperdiploid, ERG/DUX4), bi-allelic LZTR1-mutated cases showed delayed minimal residual disease clearance and higher late relapse risk, identifying a subgroup unsuitable for treatment de-escalation. LZTR1 expression was increased in most wild-type leukemias, consistent with a compensatory response to aberrant RAS pathway activation. Bi-allelic LZTR1 inactivation abolished RAS regulation, leading to deregulated canonical RAS expression and ectopic expression of the non-canonical RIT1 protein, whose involvement in ALL has not previously been reported. These findings establish LZTR1 as a classical tumor suppressor in ALL via a two-hit model. Monoallelic alterations show insufficient signaling perturbation and low germline penetrance, whereas bi-allelic inactivation acts as a driver event linked to a high risk of late relapse despite favorable genomics.

Purpose: Adults with high- or very high-risk acute leukemia (AL) or myelodysplastic syndrome (MDS) face substantial relapse risk after allogeneic hematopoietic stem-cell transplantation. We evaluated single-unit cord blood (CB) transplantation after ex vivo expansion with UM171 in this population. Patients and Methods: Two prospective, single-arm phase II trials at four centers enrolled 64 adults with high- or very high-risk AL or MDS; 60 received a UM171-expanded CB transplant and comprised the analysis population. CB units were preferentially selected at a 5/8 HLA match to maximize the graft versus leukemia effect. Patients received intermediate- or high-intensity conditioning with tacrolimus/mycophenolate mofetil graft-versus-host-disease (GVHD) prophylaxis. Endpoints included safety, feasibility, non-relapse mortality (NRM), relapse-free survival (RFS), overall survival (OS), GVHD, GVHD-free relapse-free survival (GRFS), chronic GVHD-free relapse free survival (CRFS). Results: Thirty-two percent of patients had undergone previous transplantation, 17% of patients with AL were not in remission and 24% of those with AML/MDS had TP53 mutations. Of 62 patients who remained eligible for transplantation, 60 had a graft successfully manufactured and infused. Median times to neutrophil and platelet engraftment were 17 and 38 days, respectively. NRM was 5.1% at day 100 and 15.2% at 1 year. Two-year cumulative incidence of relapse was 22.3%. Two-year OS and RFS were 63.9% and 60.4%, respectively. Grade III-IV acute GVHD incidence was 20.3% at 1 year and moderate-to-severe chronic GVHD incidence was 6.8% at 2 years. Conclusion: UM171-expanded CB transplantation was feasible and provided prompt engraftment, durable disease control, and infrequent clinically significant chronic GVHD in adults with high- and very high-risk AL/MDS. Comparative studies are warranted to define its role relative to contemporary donor platforms.

Acute myeloid leukemia (AML) is a clinically heterogeneous disease. Although the genetic abnormalities associated with poor prognosis are well defined, how they drive unfavorable outcomes remains unclear. Using published gene-expression and dependency datasets, we searched for cell-surface protein-coding genes associated with poor survival and required for AML growth, prioritizing this class of proteins for its accessibility to biologics. This search identified CD59, a GPI-anchored protein with a canonical role in complement regulation, whose high mRNA expression correlates with adverse-risk genetics and stemness signatures. CD59 silencing impaired proliferation across genetically diverse AML cell lines, reduced leukemic burden, and extended survival in cell xenograft models. Moreover, CD59 expression was enriched on leukemic stem cells (LSCs), and its depletion impaired LSC self-renewal and primary AML engraftment in vivo while sparing normal hematopoiesis. Mechanistically, these effects reflected a non-canonical role for CD59 in sustaining Ras-MAPK signaling, whereby its loss depleted inner-leaflet phosphatidylserine and impaired Ras and c-Raf membrane recruitment and activation. rILYd4, a recombinant fragment of the bacterial toxin intermedilysin that binds and degrades CD59, recapitulated these effects and sensitized cells to venetoclax in vivo. These findings reveal CD59 as a critical regulator of Ras-MAPK signaling required for AML growth and nominate its rILYd4-mediated degradation as a therapeutic strategy.

Erythroferrone (ERFE) is an erythroblast-secreted hormone that suppresses hepatic hepcidin expression to increase iron availability for erythropoiesis, ensuring recovery from anaemia. ERFE excess drives iron overload in disorders of ineffective erythropoiesis. Despite its pivotal role in systemic iron homeostasis and diseases of erythropoiesis, ERFEs molecular regulation has remained undefined. Here, we applied a genomic approach to characterise the molecular mechanisms governing ERFE expression. Using the HUDEP-2 human erythroid progenitor model, integrative ATAC-seq, CUT&RUN and micro capture-C analysis we identified a stage-specific accessible chromatin region within the ERFE 3 UTR that interacts with the promotor. We also identified enhancer-associated chromatin marks including H3K4me1 and H3K27ac in this region, and demonstrate that this cis-regulatory element is bound by key erythroid transcription factors KLF1, GATA1, TAL1 and STAT5. Functional dissection using CRISPR-Cas9-mediated deletion of the central 3 UTR enhancer element led to marked reduction in ERFE mRNA expression, and we show a corresponding reduction in nascent mRNA, confirming a key role for this region in transcriptional regulation. We define the transcriptional regulatory mechanism by which maturing human erythroblasts activate ERFE, the endocrine signal that coordinates erythropoietic demand with systemic iron mobilisation.

Chronic myelomonocytic leukemia (CMML) is an aggressive hematologic malignancy characterized by excess inflammatory signaling and clonal myeloproliferation. The relative contribution of neutrophils (PMNs) to the inflammatory milieu in CMML is poorly understood. In this study we sought to understand whether neutrophil extracellular trap (NET) formation, a key mediator of neutrophilic inflammation, is dysregulated in CMML and can be therapeutically targeted with a novel peptide inhibitor of NETosis called neonatal NET-inhibitory factor (nNIF). Here, we demonstrate that baseline NET formation is aberrantly increased in primary CMML PMNs transcriptionally primed for NETosis, and that soluble factors produced during CMML NET formation promote clonogenicity in CMML CD34+ hematopoietic cells matched to the same patient. Further, we show that nNIF and clinical agents under investigation in CMML effectively inhibit NETosis, warranting further study of NET inhibitory agents in this rare disease with limited treatment options.

Background: Promoters have been traditionally seen as contiguous gene-adjacent cis-regulatory elements. Yet, substantial studies corroborate that Epromoters (promoters with enhancer activity) engage in distal forms of gene regulation. Although in the three-dimensional (3D) space enhancer-promoter networks have been well studied, the contribution of the circuits of promoter-promoter (P-P) interactions is poorly understood. Furthermore, whether the regulatory aspects of P-P interactions in cancer may be controlled by physical 3D-mediated Epromoter interactions remains elusive. Results: We show that Epromoter-mediated 3D interactions regulate target genes and participate in cluster co-regulation, playing a critical role in T-cell acute Lymphoblastic Leukemia (T-ALL). To achieve this, we first leveraged survival CRISPR screenings in T-ALL model cells (Jurkat) to identify potential Epromoters. By integrating these findings with an H3K27ac HiChIP dataset from T-ALL cells, we characterized a set of Epromoters that establish 3D genome interactions with other promoters. We observed that promoters organize into dense, promoter-rich genomic clusters, and that among them, the clusters enriched with Epromoters actively regulate complex gene expression networks. To investigate gene coregulation, we integrated transcriptomic data from T-ALL patients and found that promoter-promoter (P-P) pairs exhibit positive correlation at multiple levels, and that several Jurkat Epromoter candidate clusters are significantly co-regulated in the patient cohort. To experimentally validate these candidates, we utilized CRISPRi to inhibit Epromoters, which revealed direct transcriptional regulation of multiple target genes within each hub. Finally, we performed cell competition assays to confirm that these Epromoters are vital for T-ALL cell survival. Conclusions: Our analysis provides support for the role of Epromoters in the regulation of 3D P-P interactions and co-regulation of promoter hubs, and how these interactions play a critical part in T-ALL cell survival.

T-cell acute lymphoblastic leukemia (T-ALL) is a heterogeneous hematologic malignancy in which LMO2 {gamma}{delta}-like T-ALL represents a rare but clinically aggressive subtype associated with poor treatment response and inferior survival. Integrated transcriptomic analyses identified high SOX11 expression as a defining feature of high-risk LMO2 {gamma}{delta}-like T-ALL, where elevated SOX11 levels correlated with refractory disease and poor clinical outcome. To investigate the functional role of SOX11 in {gamma}{delta} T-cell biology and leukemogenesis, we generated a conditional R26-SOX11 mouse model enabling lineage-specific SOX11 overexpression in T-cell progenitors. SOX11 expression promoted expansion of the innate {gamma}{delta} T-cell compartment in thymus, spleen, and bone marrow, accompanied by transcriptional activation of {gamma}{delta} T-cell differentiation, activation, and cytotoxicity programs. However, SOX11 overexpression alone was insufficient to induce leukemia or confer thymocyte self-renewal capacity. In contrast, combined SOX11 and LMO2 overexpression markedly accelerated T-ALL development and strongly increased the incidence of {gamma}{delta}-like leukemias, thereby recapitulating the human high-risk LMO2 {gamma}{delta}-like T-ALL subtype. Mechanistically, SOX11 expanded the pre-leukemic DN3 thymocyte compartment in LMO2-driven mouse model while promoting differentiation toward the {gamma}{delta} lineage. Transcriptomic profiling identified activation of MYCN-associated transcriptional programs in SOX11/LMO2 pre-leukemic thymocytes. Consistently, MYCN was highly expressed in human LMO2 {gamma}{delta}-like T-ALL, and recurrent stabilizing MYCN P44L mutations were enriched in this subtype. Functional validation using genetic and transplantation-based mouse models demonstrated that SOX11 cooperates with MYCN to accelerate T-ALL onset. Together, these findings establish a cooperative SOX11-MYCN oncogenic axis driving {gamma}{delta}-like T-ALL and provide a novel preclinical model for investigating therapeutic vulnerabilities in this high-risk leukemia subtype.

Acute myeloid leukemia (AML) is an aggressive blood cancer characterized by high rates of relapse and poor outcomes, especially in elderly or unfit patients, who cannot tolerate intensive chemotherapy. While the BCL2 inhibitor venetoclax has improved initial responses in this high-risk population, relapses remain nearly universal, highlighting the need for novel therapeutic strategies. Here, we identify the RNA-binding protein PTBP1 as a critical dependency in AML. PTBP1 depletion impairs leukemic growth in vitro and in vivo, and is associated with widespread splicing alterations and global disruption of protein synthesis. Integrative transcriptomic and iCLIP analyses reveal that PTBP1 orchestrates a splicing program centered on Rho GTPase signaling, with CDC42 as a key downstream effector. Mechanistically, PTBP1 loss triggers a splicing switch from CDC42-v1 to CDC42-v2, leading to reduced GTPase activity and impaired protein synthesis. Pharmacological inhibition of CDC42 selectively induces cytotoxicity in AML cells, while sparing healthy hematopoietic cells. Importantly, CDC42 inhibition markedly enhances venetoclax anti-leukemic efficacy. These findings establish PTBP1 as a critical regulator of AML cell fitness and identify a clinically actionable therapeutic combination that exploits AML dependency on PTBP1-CDC42 signaling to enhance the efficacy of venetoclax-based regimens.

Adult T-cell leukemia/lymphoma (ATL) is a highly aggressive leukemia driven by Human T-cell Leukemia Virus type 1 (HTLV-1) and remains largely refractory to current therapies. Although hbz is the only viral transcript consistently expressed in acute ATL, the extent to which its alternative splicing shapes disease biology remains unknown. Here, we demonstrate that the splicing of hbz plays a key role in driving cancer development in ATL. Quantitative analyses in HTLV-1-infected cell lines and primary samples revealed a striking enrichment of the spliced isoform HBZ_SP1 (over 200-fold) in CD4 T cells from ATL patients, whereas the unspliced transcript (usHBZ) predominates in CD8 T cells. Despite robust transcription, the usHBZ protein was undetectable, whereas HBZ_SP1 accumulated rapidly, identifying it as the main isoform in CD4 T cells from ATL patients. Furthermore, only HBZ_SP1 drove cellular transformation and conferred marked resistance to chemotherapeutic stress. Mechanistically, we identify a splicing regulatory axis centered on hnRNPA1 and hnRNPH1. Both proteins bind hbz pre-mRNA, but exert opposing effects: hnRNPA1 represses splicing, whereas hnRNPH1 promotes production of the oncogenic HBZ_SP1 isoform. Perturbation of this balance reprograms HBZ isoform expression and alters leukemic cell fitness. Collectively, our findings establish that HBZ inhibits hnRNPA1 transcription, therefore allowing HTLV-1 to hijack host RNA splicing and to generate an oncogenic isoform that drives transformation and chemoresistance. These results uncover a previously unrecognized post-transcriptional mechanism of viral leukemogenesis and position HBZ splicing and its regulators as therapeutic targets in ATL. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/739521v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@dad81forg.highwire.dtl.DTLVardef@1a2f134org.highwire.dtl.DTLVardef@898fd0org.highwire.dtl.DTLVardef@140a71e_HPS_FORMAT_FIGEXP M_FIG C_FIG Mechanistic model of HBZ splicing regulation. This simplified graphical abstract summarizes the highlights of our study. Here, we hypothesize that in CD4+ T cells infected by HTLV-1, transcription and splicing reprogramming lead to a preferential expression of the HBZ_SP1 oncogenic isoform, specifically due to an overexpression of the splicing activator hnRNP H1and repression of hnRNP A1 by HBZ itself via C/EBP. HBZ_SP1 is consistently expressed and then drives cell transformation and chemoresistance. In contrast, in CD8+ T cells infected with HTLV-1, the HBZ-mediated downregulation of hnRNP A1 is overcome, leading to inhibition of HBZ splicing and increased expression of the less oncogenic isoform usHBZ.

In human acute myeloid leukemia (AML), a sub-population of leukemia stem cells (LSCs) drive disease initiation, therapeutic resistance, and relapse. However, the lack of reliable markers to distinguish LSCs from bulk leukemia cells has impeded progress in studying LSC pathogenesis and developing meaningful LSC-specific diagnostics and therapeutics. Existing LSC gene signatures, derived from bulk populations, cannot definitively identify LSCs at single-cell resolution. To address this, we analyzed large patient cohorts with bulk gene expression data and single-cell multi-omic assays to identify a prognostic gene signature that is specifically enriched in a clinically adverse AML sub-population. Using this signature, we defined and prospectively isolated CD34+CD90-CLL1-CD69+CD53- immunophenotypic LSCs that are significantly enriched for LSC content based on limiting dilution xenotransplantation assays. Our findings demonstrate the power of single-cell multi-omics to precisely identify a clinically relevant LSC population and establish a clear framework for future translational research in AML. Key PointsO_LISingle cell multi-omics identifies human AML LSCs at high resolution. C_LIO_LIHOPX and SOCS2 co-expression (hrLSC2) defines a prognostic gene signature in de novo acute myeloid leukemia. C_LIO_LIhrLSC2 marks an AML subpopulation (iLSCs) with a distinct immunophenotype. C_LIO_LIiLSCs can be purified using flow cytometry and are significantly enriched for LSCs. C_LI

Myelofibrosis (MF) originates from the stepwise acquisition of somatic mutations in Hematopoietic Stem and Progenitor Cells (HSPCs). Alongside driver events triggering JAK-STAT pathway hyperactivation, several additional mutations, usually affecting the epigenetic machinery, contribute defining therapeutic response. Specifically, JAK-inhibition (JAKi) relieves MF symptoms but rarely eradicates the neoplastic clone. To elucidate clonal dynamics associated with JAKi, we conducted a longitudinal single-cell proteogenomic study on 6 responders and 6 non-responders MF patients. Mutational analysis revealed that the mutation acquisition order determines JAKi sensitivity. Indeed, driver-only clones are highly sensitive to JAKi, while co-mutated clones persist after treatment. JAKi response is mainly limited to the differentiated myeloid compartment, while mutant HSPCs are often maintained in JAKi-responders. Co-mutated clones may evade JAKi and outcompete other neoplastic cell populations, thus contributing to disease persistence.

The circulating blood proteome provides a systemic readout of disease biology and holds promise for advancing diagnostics and disease monitoring in pediatric leukemia. Here, we profiled 3072 proteins in diagnostic serum from 54 children with acute lymphoblastic leukemia (ALL), 21 with acute myeloid leukemia (AML), and 12 healthy controls using the Olink Proximity Extension Assay. We observed profound alterations in circulating protein levels in leukemia patients compared with controls and identified immunophenotype-specific proteins, including SIGLEC15 in B-cell precursor ALL (BCP-ALL), NOTCH1 in T-ALL, and CEBPA in AML, all which remained high even in patients with low (<20%) or no peripheral blood blasts. Within BCP-ALL, molecular subtypes were reflected in the circulating proteome; for example, DSC2 and PTPRK were elevated in ETV6::RUNX1-positive cases, while IL-6R and ADAM8 were higher in High Hyperdiploid cases. Angiogenic growth factors decreased across all leukemia patients compared with controls, suggesting a fragile peripheral vasculature at diagnosis. Integration with external datasets revealed the likely cellular source of abundant proteins and examination of an external cohort validated our subtype-specific findings. Together, these results define shared and distinct proteomic signatures across pediatric acute leukemias and highlight candidate biomarkers for diagnostics and disease monitoring.

Sickle-hemoglobin-C (HbSC) sickle cell disease is characterized by RBC dehydration (xerocytosis), which promotes polymerization of HbS. HbSC causes substantial morbidity despite lower sickling potential than HbSS, suggesting a critical detrimental role of HbC in the disease pathophysiology. We derived HbCC mice by interbreeding our HbSC mice, which demonstrated a similar RBC phenotype of xerocytosis as humans with HbCC. We compared RBCs from HbCC, HbSC, and HbSS mice. Oxidized ferryl (Fe4+)-Hb, and its oxidative-denaturation, which results in hemichrome formation (Heinz-bodies), was most pronounced in HbCC>HbSC>HbSS, despite significantly higher reactive oxygen species in HbSS, illustrating a higher propensity of HbC to denaturation than HbS. RBC deformability followed a similar pattern, with Elongation Index lowest in HbCC<HbSC<HbSS. Next, we determined if RBC from HbSC patients on hydroxyurea showed improved membrane damage. Hydroxyurea treatment reduced Heinz-body formation and improved RBC deformability, despite negligible/modest fetal hemoglobin (HbF) induction, compared to non-hydroxyurea HbSC controls. The antioxidant quercetin showed a similar reduction in Heinz-body burden and improvement in RBC deformability as hydroxyurea, without affecting Hb or HbF concentration, reticulocyte count, or RBC xerocytosis. HbC-driven oxidative denaturation and membrane damage represent important contributors of RBC dysfunction in HbSC disease; hence, oxidative membrane injury could be targeted besides antisickling approaches.

Chromatin regulation critically influences gene expression and cancer progression, yet the functions of chromatin adaptors remain incompletely defined. Using focused CRISPR screening, we identified TRIM28, a multi-domain chromatin adaptor, as a dependency in acute leukemia, where its depletion impaired leukemia cell proliferation in vitro and in vivo, while activating neutrophil differentiation programs. Integrative transcriptomic and chromatin profiling revealed that TRIM28 acts as a co-repressor of neutrophil-associated loci independently of H3K9 methylation, and that TRIM28 loss drives terminal differentiation of leukemia cells into functionally mature neutrophil-like cells with reduced leukemic potential. We developed a selective small-molecule TRIM28 inhibitor that binds the TRIM28 PHD-bromodomain, phenocopies TRIM28 loss across biochemical and cellular assays, exhibits low micromolar anti-leukemia activity, induces neutrophil differentiation, and synergizes with Menin inhibition. Together, these findings, spanning target discovery, mechanism of action, and chemical probe development, establish TRIM28 as a regulator of myeloid cell fate and a promising pro-differentiation therapeutic target in acute leukemia.

Adult long-term hematopoietic stem cells (LT-HSCs) are classically defined by self-renewal, multilineage regenerative capacity, and relative quiescence, but how and when lifelong LT-HSCs are established during development remains unclear. Here, we demonstrate that Hoxb5 fetal liver HSCs exhibit bona fide LT-HSC activity, including long-term multilineage reconstitution and serial transplantation capacity, whereas Hoxb5- fetal liver HSCs display limited regenerative potential. Embryonic lineage tracing further demonstrates that E14.5 Hoxb5-expressing hematopoietic cells contribute broadly to adult hematopoiesis, including the adult HSC compartment, and give rise to functional adult LT-HSCs. Across developmental stages, single-cell transcriptional profiling revealed that fetal Hoxb5 HSCs remain highly proliferative while maintaining canonical LT-HSC transcriptional programs and superior repopulating activity relative to predominantly quiescent adult Hoxb5 HSCs. Fetal Hoxb5 HSCs also exhibited elevated ITGA4-mediated adhesion programs, and disruption of the ITGA4-VCAM1 axis impaired engraftment following transplantation. Together, these findings establish a developmental continuum linking fetal and adult LT-HSCs and identify enhanced ITGA4-mediated adhesion as a defining feature of fetal LT-HSCs.

Molecular testing in hematology requires different assays for disease subgroup identification, risk stratification and selection of appropriate treatment regimens. Yet, molecular tests are not necessarily standardized between diagnostic laboratories, resulting in varying turnaround times and potentially divergent results. To resolve this issue and enable single-assay molecular testing, we have developed a hierarchical classification framework that combines epigenetic and genetic data from whole genome nanopore sequencing (WGNS) with machine learning to determine disease entities, epigenetic subgroups (epitypes) and genetic aberrations in hematopoietic neoplasms. We curated DNA methylation data from 5,420 samples and trained a classifier allowing entity-level diagnostics featuring 21 conditions, including healthy controls, acute and chronic myeloid and lymphoid neoplasms. This classifier was subsequently combined with entity-specific epitype classifiers predicting 44 therapeutically or prognostically relevant states, followed by integration of genetic data. Benchmarking of the combined (epi-)genetic testing strategy using WGNS confirmed high accuracy in the detection of diagnostic groups and risk stratification, and identified diagnosis-defining molecular alterations that were not reported by standard-of-care work-up.