EMBO Molecular Medicine

Despite considerable advances, the emergence of treatment resistance to tyrosine kinase inhibitors (TKIs) therapy remains a significant challenge in chronic myeloid leukemia (CML). Here, we report the first clinical case of resistance to combined ponatinib and asciminib therapy in a CML patient who relapsed with B lymphoblastic blast crisis. While at presentation the patient harbored the canonical e13a2 BCR::ABL1 fusion, at relapse his disease harbored the T315I mutation together with a novel e6a3 BCR::ABL1 fusion, arisen by internal deletion in the original translocated allele. Structural modeling and biochemical analyses demonstrated that deletion of exon 2-encoded residues of ABL1 destabilizes the autoinhibited conformation, resulting in a hyperactive kinase with increased propensity for B-cell differentiation. Functional studies revealed that both BCR::ABL1e6a3 and BCR::ABL1e6a3/T315I conferred resistance to ponatinib and asciminib, alone or in combination. BCR::ABL1e6a3 demonstrated enhanced sensitivity to active-state selective inhibitors dasatinib and bosutinib, whereas BCR::ABL1e6a3/T315I remained resistant. Combined drug sensitivity assays showed that axitinib restored inhibitory activity when combined with ponatinib or asciminib. Strikingly, a combination of axitinib and asciminib with low dose ponatinib fully suppressed enzymatic activity of BCR::ABL1e6a3/T315I and cellular proliferation. These data show that treatment with asciminib and ponatinib can select for mutations with notably elevated enzymatic activity, effectively targeted by an axitinib-based triple combination. These data highlight the remarkable mutability of the BCR::ABL1 kinase, including through novel isoforms and provides a strong rationale for the clinical assessment of a triple inhibitor combination as a strategy to overcome resistance to dual ponatinib and asciminib therapy.

PrP lowering is a validated therapeutic hypothesis in prion disease. To identify small molecules that reduce PrP levels, we performed phenotypic screening in cultured cells. To prioritize PrP specificity in our primary screen, we generated mouse N2a cells stably expressing GFP and used high content imaging analysis to select compounds that lowered PrP without affecting GFP signal or cell viability. Screening a curated library of 3,492 compounds with annotated mechanisms of action identified two small molecules, EYH (PubChem CID: 71678945) and LCZ (PubChem CID: 24970350), that selectively and dose-dependently lowered PrP. Proteomics on whole cell lysates identified PrP as the #1 or #2 most potently downregulated out of 8,722 proteins detected. Both compounds minimally affected Prnp mRNA, reduced expression of exogenously transfected PrP, and remained potent in non-dividing primary cells, consistent with a post-translational mechanism. Co-treatment with the proteasome inhibitor MG132 yielded accumulation of unglycosylated PrP, demonstrating proteasome clearance of PrP. However, both compounds showed limited or no activity in human cell lines, and failed to reduce PrP in vivo after 14 days of treatment. These findings highlight the challenges associated with mechanism-agnostic phenotypic screening for PrP-lowering compounds and support prioritizing compounds with known mechanisms of action.

Loss-of-function mutations in the ABCA4 gene cause Stargardt disease (STGD1), the most common inherited macular dystrophy leading to progressive central vision loss. Here, we generated hiPSC-derived retinal organoids harboring a premature stop codon in exon-24 of ABCA4 to evaluate the impact of this mutation on mRNA and protein levels in a human model. Immunofluorescence analysis revealed the absence of ABCA4 protein in the mutant photoreceptor outer segment discs, while single-cell RNA sequencing detected no major transcriptional alterations in rods and cones. Unexpectedly, differential gene expression and pathway enrichment analyses of Muller glial cells (MGCs) and astrocytes highlighted disruption of neuronal development, microenvironment of glial cells, intercellular communication, and programmed cell death pathways. These findings suggest that ABCA4 might play a role in maintaining the retinal microenvironment homeostasis, and that the early transcriptomic response of MGCs and astrocytes preceding photoreceptor degeneration could contribute to Stargardt disease development. Significance StatementHuman induced pluripotent stem cell (hiPSC)-derived retinal organoids provide a powerful platform to investigate inherited retinal diseases. In this study, we generated ABCA4-mutant hiPSC lines and differentiated them into retinal organoids to model Stargardt disease. Despite complete loss of ABCA4 protein from the photoreceptor outer segment discs, rods and cones exhibited minimal transcriptional alterations. In contrast, the ABCA4 variant triggered changes in the glial cell homeostasis, suggesting that Muller glial cells and astrocytes might exhibit an early response to photoreceptor dysfunction in the absence of ABCA4. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/718110v1_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@1d8dbf6org.highwire.dtl.DTLVardef@51239corg.highwire.dtl.DTLVardef@f8fbdborg.highwire.dtl.DTLVardef@5f0b44_HPS_FORMAT_FIGEXP M_FIG Human induced pluripotent stem cells (hiPSCs) were engineered to generate ABCA4-mutant cell lines, later differentiated into retinal organoids as a model of Stargardt disease. The organoids showed loss of ABCA4 from the outer segment discs of rod and cone photoreceptors, while the mutant Muller glial cells and astrocytes exhibited transcriptional changes in pathways involved in neuronal development, microenvironment, and programmed cell death. C_FIG

Sickle cell disease (SCD) is caused by the production of an abnormal adult hemoglobin that generates sickle-shaped red blood cells (RBCs). Transplantation of autologous genetically corrected hematopoietic stem/progenitor cells (HSPCs) represents a promising therapy. Persistent fetal hemoglobin expression improves SCD. Here, we engineered the fetal HBG1/2 promoters by replacing the BCL11A repressor binding site (BS) with a TAL1:GATA1 motif recognized by transcriptional activators. We exploited the prime editing nuclease (PEn) that efficiently installed the TAL1:GATA1 motif in K562 cells, outperforming the original PE. Non-homologous end joining (NHEJ) and/or alternative-end joining (alt-EJ) pathway inhibition enhanced precise editing. However, this strategy was poorly efficient in patients HSPCs. Alternatively, we used CRISPR/Cas9 nuclease to either disrupt the BCL11A BS via NHEJ and/or alt-EJ or to replace it with the TAL1:GATA1 motif via homology-directed repair (HDR) using a donor ssODN template. NHEJ and alt-EJ inhibition improved product purity, reducing InDels and achieving superior precise editing efficiency compared to PEn in K562 and HSPCs. HDR-edited HSPCs preserved clonogenic capacity and differentiated into RBCs showing elevated HBG expression and correction of the sickling phenotype. These results demonstrate that replacing the BCL11A BS with a TAL1:GATA1 motif is a potent strategy for reactivating HBG1/2 to treat SCD.

Understanding age-related cellular dysfunction in the brain is essential for developing strategies to promote healthy ageing. Towards this aim, we took advantage of a previously established mild dissociation method to profile cells in the cerebral cortex grey matter of adult and aged mice. This revealed glial cells with largely up-regulated and other glia and neurons with largely down-regulated gene expression upon ageing. Astrocytes were involved in increased interactions with microglia and decreased interaction with neurons, high-lighting potent age-induced changes in their regulatory roles. Single cell RNA-seq and single nuclei multiome analysis of astrocytes uncovered down-regulation of Wnt-signalling with increased expression of its inhibitors and reduced RNA and protein levels of its effectors JunB/D, acting downstream of Wnt signalling in ageing. This was confirmed by RNA-scope and immunostainings, as well as in human data. Notably, injection of JunD-expressing viral vectors in astrocytes increased their proliferation and HMGB1 levels in the aged brain, indicative of a more youthful astrocyte state. Main pointsO_LITranscriptomic analysis uncovers cell type-specific impact of ageing in the cortical grey matter, including altered intercellular communication networks. C_LIO_LIMultiomic profiling identifies dysregulated Wnt signalling in ageing cortical astrocytes. C_LIO_LIAgeing astrocytes exhibit upregulation of the Wnt signalling regulators Maml2 and Daam2, accompanied by downregulation of the AP-1 transcriptional complex component JunD. C_LIO_LIOverexpression of JunD increases proliferation after mild injury in aged astrocytes. C_LI

Antipsychotic drugs are the first-line treatment for psychosis yet their mechanism of action remains poorly understood, largely due to the challenge to faithfully model psychosis preclinically. Here, we focus on the emerging concept that psychosis can be caused by brain autoimmunity and present a novel mouse model of anti-N-methyl-D-aspartate-receptor (anti-NMDAR) encephalitis, a condition that manifests with psychosis and autoanti-bodies against the NMDAR. We devised a new mRNA-based approach to immunize mice against the NMDAR. Immunized mice developed psychosis-like behaviors that were caused by anti-NMDAR autoantibodies leading to phagocytosis of NMDARs by brain microglia. The antipsychotic drug clozapine rescued psychosis-like behaviors and, remarkably, reduced anti-NMDAR autoantibody levels and antibody-mediated phagocytosis of NMDARs. The immunomodulatory effects of clozapine were confirmed in a mouse model of systemic lupus erythematosus. Our results demonstrate that clozapine suppresses autoimmunity driving psychosis-like behaviors, raising the possibility that immunomodulation contributes to antipsychotic drug action. HIGHLIGHTSO_LImRNA immunization against the NMDAR induces psychosis-like behavior in mice C_LIO_LIAnti-NMDAR autoantibodies are sufficient for psychosis-like behavior C_LIO_LIMicroglial phagocytosis of NMDARs mediates psychosis-like behavior induced by anti-NMDAR autoanti-bodies. C_LIO_LIClozapine reduces anti-NMDAR autoantibodies, microglial phagocytosis and psychosis-like behavior, consistent with immunomodulation as a potential mechanism of antipsychotic drug action. C_LI

Type 2 diabetes and prediabetes affect hundreds of millions of people globally, yet the metabolic networks underlying disease development remain poorly understood. Using untargeted liquid chromatography-mass spectrometry (LC-MS/MS), we profiled a total of 15,470 (900 known) serum metabolite features across the human diabetes spectrum (the most comprehensive coverage reported to date). Weighted coexpression network analysis of samples from people with normal glucose tolerance, prediabetes, and type 2 diabetes, collected at baseline and 2 hours after an oral glucose tolerance test, revealed tightly coregulated modules strongly associated with glycemic dysregulation, insulin resistance, and islet dysfunction. Notably, short-chain organic acids, particularly crotonic acid, emerged as hubs of the diabetes-associated networks, accumulating progressively with disease severity. Reanalysis of extracellular vesicle proteomics from the same cohort showed that 16.5% of circulating proteins were crotonylated, with 47.6% correlated with crotonic acid and other hub metabolites, establishing a metabolome-crotonylome axis as a novel mechanism in diabetes development.

The replacement of a single codon in the human prion gene, causing the substitution of glycine with valine at position 127 (G127V) of the prion protein (PrP), prevents development of prion disease. We set out to explore if prion disease survival extension manifests in mice if the V127 mutant is delivered through a recombinant adeno-associated virus (rAAV) packaged as a self-complementary DNA. The notorious delivery limitations of rAAVs were overcome using a cross-correction approach that relied on the expression of the mutation in the context of glycosylphosphatidylinositoI-anchorless ({Delta}GPI) PrP. In this proof-of-concept study, we inoculated Rocky Mountain Laboratory (RML) prions into knock-in mice, in which the endogenous murine prion protein gene (Prnp) was replaced with the bank vole prion protein gene (BvPrnp). Prion-inoculated mice that were retro-orbitally transduced with a protective rAAV vector encoding BvPrnpV127{Delta}GPI survived [~]50 days longer than control mice that were unprotected. A deep proteomic analysis revealed that BvPrnpV127{Delta}GPI was protective by slowing perturbations to the proteome observed in late-stage RML prion disease. In addition to capturing details of synaptic decay and depletion of proteins in proximity to PrP, the proteomic dataset revealed the identity of proteins of potential diagnostic value that may be central to the brains attempt to fight prion disease by contributing to astrocytosis or microgliosis, by coping with calcium influx, or by enhancing the endoplasmic reticulum processing of essential proteins. Taken together, our results demonstrate that a gene therapy based on a GPI-anchorless PrP containing the G127V mutation can delay the onset of prion disease in mice, providing a framework for development of a corresponding therapy in humans. AUTHOR SUMMARYA rare change in the human prion protein, involving a single building block, has been linked to strong protection against prion diseases--fatal neurodegenerative disorders. This study tested whether that protective effect could be reproduced using gene therapy in mice. To this end, we exposed the animals to infectious prions and then delivered the protective version of the protein into mice using a viral carrier. Treated mice survived about seven weeks longer than untreated animals, showing that the approach can meaningfully slow disease progression. To understand why, we examined changes in brain proteins during disease and found that treatment helped preserve the normal protein levels of cellular proteins, particularly those involved in communication between nerve cells. The analysis also identified proteins altered in the disease that are linked to the brains defense responses, including inflammation, stress handling, and protein processing, some of which may serve as future disease markers. Importantly, the limited protection observed was not due to poor delivery of the therapy but likely reflects biological limits of the model used. Overall, the findings support the idea that gene therapies based on naturally protective human variants could help slow prion diseases and improve understanding of how the brain responds to them.

Background: Genetic variants impacting red blood cell biology disrupt the relationship between glycaemia and glycated haemoglobin (HbA1c), with implications for diagnosis and management of type 2 diabetes (T2D). Thalassaemia trait is estimated to affect 350 million people globally, but its impact on T2D and related outcomes is not clear. Methods: We explored associations between thalassaemia trait, HbA1c, and T2D diagnosis and complications in 43,088 British Bangladeshi and Pakistani participants in the Genes & Health study with linked multisource England National Health Service (NHS) electronic health record data and whole exome sequencing. Findings: 2,490 participants (5.8%) were heterozygous carriers of ClinVar pathogenic / likely pathogenic thalassaemia variants, however 3 in 4 of these were not diagnosed with thalassaemia in their NHS health records. rs33950507, a common variant causal for HbE thalassaemia, was associated with increased HbA1c (beta=0.13, 95%CI:0.08-0.18, p=7.8x10-8), but not glucose levels (beta=0.01, 95%CI:-0.04-0.06, P=0.72). rs33950507 was associated with increased hazards of prediabetes (HR=1.38, 95%CI:1.26-1.52, p=2.2x10-6) and T2D (HR=1.11, 95%CI:1.01-1.22, p=0.03), and reduced hazards of diabetic eye disease (HR=0.74, 95%CI:0.56-0.96, p=0.02) and cerebrovascular disease (HR=0.44, 95%CI:0.20-0.94, p=0.03). Sensitivity analyses suggested mediation by overdiagnosis and overtreatment of T2D. Interpretation: Alternatives to HbA1c, and/or precision medicine approaches to defining and managing hyperglycaemia, are needed, particularly on a global scale. This may be particularly relevant to individuals from ancestral groups among whom erythrocytic traits are more common but often undiagnosed. Funding: Wellcome Trust, MRC, NIHR, Barts Charity, Genes & Health Industry Consortium

Transactive response DNA binding protein 43 kDa (TDP-43) pathology, is a central molecular hallmark of amyotrophic lateral sclerosis (ALS). However, the underlying triggers are incompletely understood. Here, we show that infection with herpes simplex virus (HSV) induces molecular hallmarks of ALS in various in vitro and in vivo models and is associated with an increased risk of ALS in human population data. German healthcare provider data (n = 238,440) and herpesvirus serology of an ALS patient and control cohort (n = 1,100) showed that HSV infection elevated the ALS risk by 210% and odds by [~]65%, respectively. On a molecular level, HSV infection promoted TDP-43 pathology in neuronal cell models, human iPSC-derived motoneurons and cerebral organoids, mice, and human tissue sections. This effect was triggered by HSV-1 or 2, but not by several other related herpesviruses. Mechanistically, the infected cell protein 0 (ICP0) of HSV-1/2 drives TDP-43 pathology by disturbance of promyelocytic leukemia nuclear bodies (PML-NBs), thereby abrogating TDP-43 SUMO2/3ylation. Taken together, we reveal a previously unrecognized association between HSV infection and ALS and clarify the underlying molecular mechanism that drives TDP-43 pathology. Our data may guide future studies into therapeutic and prophylactic interventions against ALS.

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease with a heterogeneous clinical presentation, complicating early diagnosis and therapeutic monitoring. To identify disease-specific biomarkers, we performed an unbiased cerebrospinal fluid (CSF) proteomic analysis in 87 ALS patients, 89 healthy controls, and 61 neurological controls using mass spectrometry. Across all quantified proteins, 399 were significantly dysregulated in ALS, including established neurodegeneration (NEFL, NEFM, UCHL1) and neuroinflammatory (CHIT1, CHI3L1, CHI3L2) markers. Correlation and pathway analyses uncovered dysregulation of immune, synaptic, and metabolic processes, with aberrant complement activation emerging as a hallmark. Complement proteins increased progressively with declining ALS Functional Rating Scale-Revised and longer disease duration, whereas early-stage markers (CLSTN3, CHAD, RELN) indicated pre symptomatic neuronal and synaptic disruptions. Machine learning identified a minimal five protein CSF panel (MB, ITLN1, YWHAG, FCGR3A, PGAM1) that accurately distinguished ALS patients from healthy controls, capturing disease-specific pathophysiology beyond general neurodegeneration. Our findings define a robust ALS-specific CSF proteomic signature, reveal prognostic protein candidates across disease stages, and provide a framework for diagnostic biomarker development, enabling earlier intervention and monitoring.

Owing to pivotal roles in CNS debris clearance and homeostasis, microglia are central targets for the therapy of neurodegenerative diseases. Intricate proximity to neurons, the inherent danger of neuroimmune toxicity, and intrinsically high plasticity and adaptability, impose high hurdles on microglia modulation. Attenuated viruses are being tested extensively against CNS malignancies (i.e., cancer virotherapy); yet, aside from viral vector-mediated payload delivery, virotherapy for non-neoplastic CNS disease remains unexplored. Here we report disseminated targeting of microglia with the highly attenuated polio:rhinovirus chimera, PVSRIPO, that culminated in profound, durable microglia reprogramming. This phenotype, rooted in extended cytoplasmic viral (v)RNA replication, was non-cytopathogenic and did not yield virus progeny or dissemination. vRNA replication in microglia triggered selective interferon (IFN) regulatory factor (IRF) 3/IRF7 transcriptional programs in the relative absence of NF{kappa}B-driven proinflammatory cytokine responses and elicited robust phagocytosis of both tumor cells and amyloid-beta. Targeting of microglia with PVSRIPO mediated immunotherapy in a mouse glioma model and the clearance of oligomeric amyloid-beta deposits in an injectable model of neurotoxic amyloid accumulation. This work identifies attenuated virotherapy as an approach to safely and effectively invigorate microglia function in immune surveillance and neurotoxic debris clearance.

Targeting Porcupine (PORCN), a key regulator of the WNT-signalling pathway, has shown therapeutic potential in multiple cancers. Despite strong target engagement and acceptable safety profiles through human phase I clinical trials, low phase II efficacy has stalled further clinical development. Given that aberrant WNT signalling can drive tumorigenesis by inducing chromosomal instability (CIN), we hypothesised that genomic CIN signatures might serve as a predictive biomarker to help improve response rates. Using a controlled in vitro model and single-cell whole-genome sequencing, we demonstrate that acute WNT-activation directly induces three distinct types of CIN: whole genome duplication, replication stress, and impaired homologous recombination. We translated these observations into a composite CIN signature biomarker that significantly correlated with both genetic dependency and pharmacological inhibition of PORCN across 195 and 24 cell lines, respectively. Through a large-scale meta-analysis of patient-derived and cell line xenografts, we established that this composite CIN signature biomarker quantitatively predicts in vivo PORCN inhibitor sensitivity (R=-0.71, p<0.002). By applying an optimised biomarker threshold, refined through modelling of human patient data, to the The Cancer Genome Atlas dataset, we successfully retrospectively modelled previous trial results and identified gastroesophageal cancers as a high-prevalence (36.6%) indication for future development. We validated this strategy in a mouse clinical trial of gastric and esophageal xenografts, where biomarker-guided stratification achieved an objective response rate of 60% and significantly decreased risk of progression (HR=0.21, p=0.0345). These data establish an actionable, trail-ready framework for further PORCN inhibitor clinical development.

Type 2 diabetes (T2D) is a heterogeneous disease shaped by genetic pathways related to insulin resistance and beta cell dysfunction, but how this heterogeneity is reflected molecularly remains unclear. We integrated partitioned polygenic scores (pPS) with proteomic and metabolomic profiling to define molecular signatures of T2D and their clinical relevance. We analyzed UK Biobank participants with genomic, proteomic, and metabolomic data. In a disease-free training subset, we used LASSO regression to identify multi-omic signatures associated with each pPS by jointly modeling proteins and metabolites. In an independent testing set, we constructed multi-omic scores and examined their associations with clinical traits and diabetes-related outcomes. Mediation analyses were used to investigate putative causal pathways. Key findings were evaluated in the Multi-Ethnic Study of Atherosclerosis (MESA). We identified distinct multi-omic signatures that capture the molecular architecture of T2D genetic risk across physiological subtypes. Compared with genetic scores alone, multi-omic pPS showed larger effect sizes and better disease discrimination. These scores recapitulated subtype-specific physiology and were associated with T2D risk. The Beta-Cell 2 multi-omic score showed marked stratification for insulin use, which was replicated in MESA, where it also predicted future insulin use. Mediation analyses implicated lipoprotein remodeling and fatty acid metabolism in the Lipodystrophy 1 cluster, accounting for up to 45% of the total effect of pPS on T2D risk. Integrating process-specific genetic risk with circulating multi-omic profiles reveals biologically distinct endotypes of T2D and supports a framework for improved patient stratification and risk assessment.

Cerebral malaria is a severe neurological complication of Plasmodium falciparum infection. Damage of the blood-brain barrier (BBB) and endothelial dysfunction are established drivers of the disease pathology, however, whether astrocytes, a major constituent of the BBB, influence the disease outcome remains unclear. Using the murine model of experimental cerebral malaria (ECM), we show that astrocytes decisively regulate the outcome of ECM and the deubiquitinating enzyme OTUD7B in astrocytes fosters the disease. Mice lacking astrocytic OTUD7B showed reduced brain pathology and were protected from ECM compared with wildtype littermate controls. Transcriptomic profiling of ex vivo-isolated astrocytes revealed reduced proinflammatory chemokines and cytokines in the absence of OTUD7B. Plasmodium infection-associated microvesicles triggered a pro-inflammatory response in astrocytes, which was dependent on OTUD7B. Mechanistically, OTUD7B cleaved K48-linked ubiquitin chains from TRAF3 and TRAF6 upon stimulation with microvesicles or activation of TLR3/TLR9 by plasmodial nucleic acids. The OTUD7B-dependent TRAF3 and TRAF6 stabilization led to sustained NF-{kappa}B and p38 MAP kinase signaling and CXCL10 expression. Therapeutic silencing of CNS Otud7b or Cxcl10 expression after disease onset protected mice from ECM, identifying the cerebral OTUD7B-Cxcl10 axis as an attractive therapeutic target.

The RUNX1 transcription factor is a critical regulator of hematopoiesis and frequently mutated in myeloid malignancies. In the myeloproliferative neoplasm, chronic myeloid leukemia (CML), secondary somatic RUNX1 mutations and RUNX1::MECOM/EVI1, are associated with tyrosine kinase inhibitor (TKI) resistance and progression to the blast-phase (BP-CML). Research has predominantly focussed on transcriptional dysregulation mediated by RUNX1 mutations in myeloid malignancies, whilst post-transcriptional dysregulation remains comparatively unexplored. To address this, we used orthogonal organic phase separation (OOPS), to characterise the RNA-binding proteome of RUNX1 deficient BP-CML cells. RUNX1 depleted BP-CML cells exhibited significant alterations to RBP abundance involved in stress response pathways and translation/ribosome-biogenesis (RiBi). Furthermore, RUNX1 depletion or expression of RUNX1::EVI1 in BP-CML cells induced expression and RNA binding activity of SPATS2L, a component of stress granules (SG); membraneless cytoplasmic condensates protecting mRNAs from degradation, promoting survival under stress. Whilst RUNX1 depletion increased SG-assembly, SPATS2L depletion reduced SG-assembly in BP-CML cells and inhibited the growth and survival of multiple BP-CML cell lines. The translation inhibitor homoharringtonine (HHT), used historically in TKI-resistant CML, ablated SG-assembly in BP-CML cells with RUNX1 depletion, and, primary BP-CML cells with LOF/hypomorphic RUNX1 mutations (characterised by defective DNA-binding/CBF{beta}-interaction) were preferentially sensitised to HHT. Finally, suppressing SPATS2L expression induced by RUNX1 depletion, increased the HHT-sensitivity of RUNX1 depleted BP-CML cells, suggesting SPATS2L contributes to therapeutic resistance in CML with RUNX1 mutations. This study suggests that SPATS2L and SG induction could be critical to RUNX1-mutant leukemias, and, provides preliminary evidence for a mutationally-targeted approach in CML with RUNX1 aberrations.

The autosomal dominant p.Ala165Val mutation in LIM Domain Binding Protein 3 (LDB3) causes myofibrillar myopathy marked by Z-disc disruption, accumulation of filamin-C (FLNc) and chaperone proteins, and progressive muscle weakness. We previously showed that this mutation interferes with the LDB3-protein kinase C alpha (PKC)-FLNc mechanosensing axis and impairs chaperone-assisted selective autophagy (CASA), establishing a gain-of-function mechanism. In this study, we examined whether mutant allele-specific knockdown could reverse the disease or mitigate disease progression in-vivo. A single intramuscular-injection of an AAV9-delivered microRNA-based shRNA produced substantial knockdown of mutant Ldb3 transcripts and protein in Ldb3Ala165Val/+ knock-in mice treated either before or after the onset of pathology. Treatment after disease onset reduced filamin-C and CASA protein aggregates and improved muscle strength, whereas early intervention prevented development of molecular and histological features of myopathy. Phosphoproteomic profiling further showed broad remodeling of dysregulated phosphorylation networks, including restoration of PKC-responsive sites and normalization of altered sarcomeric and cytoskeletal signaling observed in Ldb3Ala165Val/+ mice. These findings identify disruption of the LDB3-PKC-FLNc mechanosensing pathway as a central disease driver and suggest that restoring this signaling axis may complement mutant allelespecific RNA interference (RNAi). Overall, our results support RNAi as a promising therapeutic strategy for dominant LDB3-related myofibrillar myopathy.

Sphingolipid homeostasis is critical for neuronal structural and functional integrity in the central and peripheral nervous systems. The rate-limiting enzyme of this pathway, serine-palmitoyltransferase (SPT), establishes the metabolic entry point into sphingolipid biosynthesis. Mutations in the SPT subunits, SPTLC1 and SPTLC2 lead to contrasting disease phenotypes in patients, including amyotrophic lateral sclerosis (ALS) and hereditary sensory neuropathy (HSAN1). A third mixed sensory-motor phenotype is attributed to distinct mutation sets in SPTLC1 and SPTLC2. However, a direct comparison of the metabolic consequences of mutations spanning these disease conditions has not been performed. Here, we demonstrate that SPTLC1- and SPTLC2-ALS variants contribute to enhanced sphingolipid flux while the ceramide-mediated homeostatic control is impaired. In contrast, HSAN1-associated variants display altered substrate selectivity, shifting flux towards non-canonical 1-deoxysphingolipid (1-deoxySL) production but decreasing canonical synthesis. The variant associated with a mixed sensory-motor phenotype exhibit a third metabolic state with elevated 1-deoxySL formation and, in contrast to HSAN1-variants, increased canonical sphingolipid synthesis. Sphingolipid profiling reveals that ALS variants are characterized by preferential accumulation of dihydro- and intermediate chain sphingolipid species. Notably, the separation of lipid species between ALS and HSAN1 is robust, with canonical sphingolipids enriched in ALS variants, while long-chain 1-deoxySL dominate in HSAN1. The SPT-variants associated with mixed sensory and motor symptoms are associated with elevated levels of both types. The data support the view that segregated shifts in sphingolipid flux underlie divergence of clinical phenotypes in SPT-variants and offer guidance for therapeutic interventions. Importantly, therapeutic strategies must account for these metabolic configurations, as L-serine supplementation may benefit HSAN1 but exacerbate pathology in ALS and sensory-motor disease conditions.

Myostatin (MSTN) is a TGF{beta} family ligand that restricts muscle growth. Genetic loss-of-function in MSTN increases muscle mass, reduces fat accumulation, and improves metabolic health in mice and humans, with no known adverse phenotypes. Thus, depleting MSTN has therapeutic potential for obesity, sarcopenia, and other muscle wasting conditions. Recently developed monoclonal antibodies (mAbs) targeting MSTN or its receptors are expensive, require frequent injections/infusions, and risk a loss of efficacy from the development of anti-drug antibodies. Here, we report a comparatively inexpensive and durable alternative to mAbs, a virus-like particle (VLP)-based active immunotherapy, termed "MS2.87-97", that elicits an antibody response against a discrete and unique epitope in mature MSTN protein, with no cross-reactivity to GDF11. Compared to controls, MS2.87-97-treated mice had less age-associated weight gain and exhibited significantly reduced body fat by DEXA scan. MS2.87-97-treated mice also had significantly improved bodyweight-adjusted grip strength, and upon dissection, they were found to have increased muscle mass. No major safety concerns were identified. Echocardiography revealed no evidence of functional impairment of the heart, and histological analysis showed no change in myocardial collagen deposition (fibrosis). These initial findings support the continued preclinical development of MS2.87-97 as an immunotherapeutic for treating obesity, sarcopenia, and muscle wasting.

Protein degrader drugs such as PROTACs are being advanced as therapeutics targeted against oncogenic proteins. During tumorigenesis, oncogenic proteins can become constitutively activated via mechanisms including gene amplification, which increases protein production, and point mutations, which can extend protein half-life. Few experimental studies have addressed how disease-associated changes in target protein homeostasis influence PROTAC activity. We developed orthogonal methods to increase production or enhance stability of {beta}-catenin, an important oncoprotein and target for degrader therapeutics, and used the dTAG system to evaluate the consequences for PROTAC activity. Stabilising oncogenic missense mutations increased protein expression up to 5-fold but do not alter the PROTAC-imposed minimal steady-state level. In contrast, transcriptional upregulation increases both pre- and post-treatment target levels, revealing a synthesis-dependent ceiling on achievable depletion. Our results highlight distinct constraints on PROTAC activity arising from different mechanisms of oncogene activation, with potential implications for preclinical modelling, drug resistance and personalised medicine.