Heterochromatin proteins play a key role in establishing local chromatin structure to control the transcription of target genes. Here we uncover a surprising segregation between regions of high DNA- and high heterochromatin protein 1 β (HP1 β )-density in mouse ES cells. DNA-low/HP1 β -high foci retain freely diffusing HP1 β , and form via condensation through a multitude of weak interactions on top of HP1 β that is bound stably to chromatin. DNA-high/HP1 β -low foci exclude freely diffusing HP1 β and display reduced chromatin mobility, suggesting a higher degree of chromatin self-interaction and a more repressive environment. Finally, the two types of environments are intertwined in DNA-high/HP1 β -high foci, where HP1 β maintains heterochromatin in a more compact yet dynamic chromatin state. During the exit from naïve pluripotency HP1 β is lost from regions of high DNA density as cells transition through the formative state, which might facilitate the reconfiguration of genome structure accompanying a change in cell state that we observed previously. Subsequently, as cells enter primed pluripotency, canonical heterochromatin is established.

Abstract Herein, we investigated the role of an essential transcription factor in the human T-cell leukemia virus type 1 (HTLV-1) provirus, the HTLV-1 basic zip factor (HBZ), in HTLV-1 infections and adult T-cell leukemia/lymphoma (ATL). We designed five synthetic guide RNAs (sgRNAs) targeting HBZ and introduced them into ATL and HTLV-1 infected cell lines using clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9 (CRISPR/Cas9). Of all sgRNAs, sgRNA 171 was the most efficient in introducing mutations at the target site as 70–80% of Cas9/sgRNA 171-transfected host cells contained mutations. Various types of mutations, including deletions, substitutions, insertion, and combinations, were detected in the Cas9/sgRNA 171-treated cells. Based on the predicted peptide sequence, most mutant clones were assumed to inactivate the HBZ mRNA. The mRNA levels of the transactivator from the X-gene region ( tax ) increased after HBZ editing by Cas9/sgRNA 171. No off-target effects were observed in the four human genome regions partially homologous to the sgRNA 171 target sequence. Furthermore, ST-1 cells transfected with Cas9/sgRNA 171 displayed significantly reduced proliferation. These findings suggest that the HBZ mRNA might be crucial for the survival of HTLV-1-infected cells, including ATL, providing insights into the molecular pathogenesis of the HTLV-1 provirus.

Abstract Mutations in ABCA4 gene causes Stargardt macular degeneration, which manifests with toxic lipofuscin deposits in the outer retina, gradual atrophy of RPE cells, followed by photoreceptor cell loss. The cone-enriched retina, with macula-like ‘area-temporalis’ of zebrafish are better models than rodents for studying human macular dystrophies. Here, we generated abca4b knockout zebrafish model using CRISPR/Cas9 editing and evaluated the early and late-stage retinal changes. In adult abca4b −/− mutants, the RPE cells exhibited hyperpigmentation, altered retinomotor behaviour and lipofuscin accumulation, but they remained viable. However, the photoreceptors underwent progressive degeneration, with a sequential loss of blue and UV cones, followed by red and green cones and finally the rod cells. This triggered the chronic activation and early depletion of retinal stem cells at the ciliary marginal zone of mutants and resulted in accelerated outer-retinal degeneration and severe visual defects, despite them retaining the Müller glia-dependant retinal repair potential.

ABSTRACT Marek’s disease (MD), a highly contagious avian immunosuppressive disorder caused by the α-herpesvirus MDV-1, poses a significant threat to poultry health. The development of rapid visual detection methods capable of distinguishing epidemic MDV-1 strains from vaccine strains is crucial for early disease warning, vaccine efficacy evaluation, and precise disease control. We developed a novel isothermal detection system that integrates recombinase polymerase amplification (RPA) with CRISPR/Cas14a technology for the visual identification of epidemic MDV-1 strains. This method operates at a constant temperature of 37°C and allows for either real-time analysis or endpoint visual readout without the need for complex instrumentation. Our results showed no cross-reactivity with Newcastle disease virus (NDV), infectious bursal disease virus (IBDV), MDV-1 vaccine strains, or herpesvirus of turkeys (HVT). Plasmid DNA standards were used to determine the sensitivity of the assay and the detection limit was 24.6 copies/μL. Clinical evaluation using 24 field samples confirmed that the method successfully identified all MDV-positive cases, demonstrating its diagnostic reliability. In conclusion, we have developed a rapid, instrument-free, and highly specific nucleic acid detection platform for MDV-1 by combining the sensitivity of RPA with the specificity of CRISPR/Cas14a technology, offering promising potential for field-based diagnostics and disease surveillance. IMPORTANCE Marek’s disease virus (MDV-1) is a highly contagious and economically important avian pathogen. Existing diagnostic methods are unable to reliably distinguish between epidemic and vaccine strains in field settings, which hampers effective surveillance and evaluation of vaccination programs. To address this challenge, we developed a portable isothermal detection assay that combines recombinase polymerase amplification (RPA) with CRISPR/Cas14a technology. This approach enables highly sensitive (24.6 copies/μL) and specific visual detection of epidemic MDV-1 strains without cross-reactivity with vaccine strains or related viruses. The assay demonstrated 100% agreement with reference methods when validated using clinical samples. As a cost-effective and instrument-free method, it offers a practical solution for rapid on-site diagnosis, facilitating enhanced outbreak control and improved poultry health management globally.

Avian influenza viruses (AIVs) are zoonotic pathogens that pose an increasing global threat due to their potential for significant economic losses in agriculture, spillover into humans, and the risk of a pandemic should human-to-human transmission occur. These concerns underscore the need for rapid, sensitive and specific tools to detect and differentiate circulating AIV subtypes and clades. Current AIV diagnostic methods rely on specialized equipment and trained personnel, limiting their use in the field and in low-resource settings. Here, we extended SHINE (Streamlined Highlighting of Infections to Navigate Epidemics), a CRISPR-based platform, to detect and subtype AIVs. We designed, optimized, and validated SHINE assay for the H5 AIV detection using both fluorescence and lateral flow readout, achieving 100% specificity with PCR-based assays when tested on seasonal influenza-positive clinical samples, and a limit of detection of 121.7 copies/μL on vaccine-derived H5 viral seedstocks. To expand the scope of avian influenza detection, we also designed and validated a SHINE assay targeting the 2.3.4.4b A(H5N1) lineage, in response to the ongoing H5N1 outbreak in cattle in the United States, and a SHINE assay specific to Eurasian H7 lineage to discriminate against North American H7 lineage. Together, these SHINE assays offer a promising platform for AIV diagnosis and surveillance, particularly in settings with limited laboratory infrastructure.

Neurological disorders often originate from progressive brain network dysfunctions that start years before symptoms appear. How these changes emerge in the developing human brain remains elusive due to a lack of tractable model systems. Here, we show a cerebral organoid model of Tuberous Sclerosis Complex (TSC) that recapitulates hallmarks of epileptogenesis in vitro. We compare extracellular recordings of TSC organoids with intraoperative electrocorticography from TSC patients to reveal striking functional similarities, including high-frequency oscillations - an electrical biomarker for epileptogenic tissue. In TSC, a human-specific interneuron sub-type derived from the caudal ganglionic eminence drives network hyper-synchronization through increased spontaneous firing and altered excitability. Inhibiting overproliferation of its progenitors via long-term epidermal growth factor receptor inhibition prevented the onset of this pathological phenotype at functional and morphological levels. Our work shows that organoids allow mechanistic analysis of emerging neural network phenotypes, enabling anti-epileptogenic drug testing in a human brain development model.

Ovarian high-grade serous cancer (HGSC) is an aggressive subtype of epithelial ovarian cancer. Here, we identify BX-912, a phosphoinositide-dependent kinase 1 (PDPK1) inhibitor, as a promising therapeutic agent for HGSC. BX-912 suppressed HGSC growth as a single agent and synergized with olaparib independently of BRCA status. Unexpectedly, BX-912 treatment induced multinucleation, a phenotype not observed with other PDPK1 inhibitors. Proteome Integral Solubility Alteration (PISA) profiling revealed the transcription factor HES1 as a functional target of BX-912. Structural modeling showed that BX-912 binds the Orange domain of HES1, while its WRPW motif mediates interactions with protein partners, including the AP2 endocytic protein complex, coordinating their nuclear accumulation that leads to a mitotic catastrophe. Furthermore, cell cycle analyses showed that BX-912 combined with olaparib synergistically enhanced DNA damage and G2-M arrest. Our study demonstrates the value of proteomics for revealing hidden drug activities. It also identifies potential inhibition strategies for HES1, which is commonly overexpressed in HGSC. Additionally, this study proposes a novel strategy of targeting consecutive cell cycle phases to enhance treatment efficacy in HGSC.

A key pathological feature of Parkinsons Disease (PD) is the loss of neuromelanin, an iron chelator within the dopaminergic neurons, which results in iron toxicity thought to result in selective neuronal vulnerability. This implicated iron handling pathways as an early target of research in PD. Given the critical role of PD-related activating mutations in LRRK2 (leucine-rich repeat protein kinase 2) within membrane trafficking pathways we examined the impact of mutant LRRK2G2019S on iron homeostasis within a model macrophage cell line known to have high iron capacity. Proteomics analysis revealed a dysregulation of iron-related proteins in steady state with highly elevated levels of ferritin light chain and a reduction of ferritin heavy chain. LRRK2 mutant cells showed efficient ferritinophagy upon iron chelation, but upon iron overload there was a near complete block in the degradation of the ferritinophagy adaptor NCOA4. Surprisingly, NCOA4 levels were not rescued upon inhibition of the LRRK2 kinase activity in iron overload conditions, nor was the phosphorylation of substrate Rab GTPases. We therefore generated a CRISPR mutation to delete the kinase domain of LRRK2 and express only the Rab-binding armadillo repeat domain. Although the kinase domain was deleted, the truncation mutant of LRRK2 showed strong Rab8 phosphorylation in conditions of iron overload, similar to LRRK2G2019S cells, with the phosphorylated Rab8 accumulating at the plasma membrane. These data indicate that the G2019S mutation acts as a kinase independent, dominant-interfering mutant specifically in conditions of iron overload. Together, our data implicate LRRK2 as a key regulator of iron homeostasis and point to the need for an increased focus on the mechanisms of iron dysregulation in PD.

ABSTRACT A scarcity of live, paralog-specific tools has limited analysis of PSD-MAGUKs at excitatory synapses. To address this gap, we engineered small, 10 FN3-derived binders that selectively recognize PSD-93 and SAP102 -alongside an enhanced PSD-95 reagent- and converted them into regulated, gene-encoded intrabodies for endogenous imaging. Through sequence-guided selection and targeted optimization, we obtained high-specificity reagents that label their native targets in neurons with minimal perturbation and support multiplexed live-cell and advanced imaging modalities. This toolkit enables differential visualization of MAGUK paralogs at native levels and provides a practical route to dissect their distinct contributions to synapse organization and plasticity.

The class 1 HDACs 1, 2 and 3 form seven families of distinct large multiprotein complexes that regulate gene expression via deacetylation of lysines in histone tails. The degree of redundancy and functional overlap between complexes and their primary gene targets, remains unknown. We used CRISPR/Cas9 to independently tag HDAC complexes with FKBP12 F36V in HCT116 cells enabling rapid ( 50% of expressed genes. More than 60% of these are specific to an individual complex. Of genes regulated by more than one complex, approaching 50% are reciprocally regulated such that HDAC complexes act as antagonistic regulators. Homer analysis strongly suggests that the complexes are reliant on different transcription factors. This is the first study to identify the primary targets of individual HDAC complexes and directly compare the effects of rapid degradation on gene regulation in the same biological system.

The diverse pigmentation patterns of animals are crucial for predation avoidance and behavioral display, yet mechanisms underlying this diversity remain poorly understood. In zebrafish, Turing models have been proposed to explain stripe patterns, but it is unclear if they apply to other fishes. In anemonefish ( Amphiprion ocellaris) , we identified gja5b , a gene orthologous to zebrafish leopard and encoding a connexin involved in pigment cell communication, as responsible for the Snowflake phenotype. Using CRISPR/Cas9 and transgenesis, we recapitulate the Snowflake phenotype and show expression of gja5b in iridophores. A matching allele was recovered in zebrafish, revealing complementary requirements in both species. Our findings highlight conserved roles of gap junction mediated communication in pigment patterning across divergent teleosts.

ABSTRACT The persistent residual tumor cells that survive after chemotherapy are a major cause of treatment failure, but their survival mechanisms remain largely elusive. These cancer cells are typically characterized by a quiescent state with suppressed activity of MYC and MTOR. We observed that the MYC-suppressed persistent triple-negative breast cancer (TNBC) cells are metabolically flexible and can upregulate mitochondrial oxidative phosphorylation (OXPHOS) genes and respiratory function (“OXPHOS-high” cell state) in response to DNA-damaging anthracyclines such as doxorubicin, but not to taxanes. The elevated biomass and respiratory function of mitochondria in OXPHOS-high persistent cancer cells were associated with mitochondrial elongation and remodeling suggestive of increased mitochondrial fusion. A genome-wide CRISPR editing screen in doxorubicin-persistent OXPHOS-high TNBC cells revealed BCL-XL gene as the top survival dependency in these quiescent tumor cells, but not in their untreated proliferating counterparts. Quiescent OXPHOS-high TNBC cells were highly sensitive to BCL-XL inhibitors, but not to inhibitors of BCL2 and MCL1. Interestingly, inhibition of BCL-XL in doxorubicin-persistent OXPHOS-high TNBC cells rapidly abrogated mitochondrial elongation and respiratory function, followed by caspase 3/7 activation and cell death. The platelet-sparing proteolysis targeted chimera (PROTAC) BCL-XL degrader DT2216 enhanced the efficacy of doxorubicin against TNBC xenografts in vivo without induction of thrombocytopenia that is often observed with the first-generation BCL-XL inhibitors, supporting the development of this combinatorial treatment strategy for eliminating dormant tumor cells that persist after treatment with anthracycline-based chemotherapy.

Cytotoxic CD8 + T-cells play central roles in tumor immunotherapy. Understanding mechanisms that regulate development, differentiation, and functions of cytotoxic CD8 + T-cells leads to development of better immunotherapies. By combining primary T-cell culture and a syngeneic mouse tumor model with both genome-wide and custom CRISPR/Cas9 screenings, we systematically identified genes and pathways that regulate PD-1 expression and functions of CD8 + T-cells. Among them, inactivation of a key enzyme in glycoconjugate biosynthesis, beta 1, 4-galatosyltransferase 1 (B4GALT1), leads to significantly enhanced T-cell receptor (TCR) activation and functions of CD8 + T-cell. Interestingly, suppression of B4GALT1 enhances functions of TCR-T-cells, but has no effect on chimeric antigen receptor T (CAR-T) cells. We systematically identified the substrates of B4GALT1 CD8 + T-cell surface by affinity purification and mass spectrometry analysis, which include protein components in both TCR and its co-receptor complexes. The galactosylation of TCR and CD8 leads to reduced interaction between TCR and CD8 that is essential for TCR activation. Artificially tethering TCR and CD8 by a TCR-CD8 fusion protein could bypass the regulation of B4GALT1 in CD8 + T-cells. Finally, the expression levels of B4GALT1 normalized to tumor infiltrated CD8 + T-cells in tumor microenvironment are significant and negatively associated with prognosis of human patients. Our results reveal the important roles of protein N-glycosylation in regulating functions of CD8 + T-cells and prove that B4GALT1 is a potential target for tumor immunotherapy.

Although glucocorticoids are widely used to alleviate side effects of prostate cancer (PCa) treatment, the glucocorticoid receptor (GR) exhibits a dual role exerting tumor-suppressive effects by inhibiting early-stage PCa cell proliferation, while also promoting oncogenic progression by mediating antiandrogen resistance. The mechanisms underlying this functional dichotomy have remained elusive and poorly characterized. Using genome-wide analyses and CRISPR-based genome editing, we identified the tumor protein p63 as a key mediator of GR’s tumor-suppressive chromatin activity. Loss of p63 reprograms GR activity toward an oncogenic state, marked by enhanced cell migration, invasion, and altered morphology. This shift is driven by increased GATA2 expression, which alters GR’s chromatin binding and transcriptional output. Together, our findings uncover a p63–GATA2 molecular switch that governs the dual role of GR in PCa, establishing transcription factor crosstalk as a critical regulator of GR-driven oncogenic reprogramming and cellular plasticity.

Chimeric antigen receptor (CAR) T cell therapies are being widely investigated in both autologous and allogeneic settings, with gene editing providing new strategies to address barriers to mismatched cell therapies. Currently ‘universal’ donor derived T cell therapies require intensive lymphodepletion and are prone to host-mediated rejection. CD38, a transmembrane glycoprotein involved in cell activation and bioenergetics, is a promising immunotherapy target for haematological malignancies. Disruption of CD38 expression using base editing prevented fratricide between T cells expressing anti-CD38 CAR (CAR38). Additional base editing enabled generation of a ‘universal’ donor CAR38-T cells, devoid of endogenous TCRαβ and Human Leukocyte Antigen (HLA) molecules after disruption of T Cell Receptor Beta Constant ( TRBC ), Beta-2 microglobulin ( B2M ), and Regulatory Factor X5 ( RFX5 ). Removal of cell surface HLA expression enabled evasion of anti-HLA antibodies in sera from sensitised donors and reduced allo-stimulation in mixed lymphocyte cultures (MLCs), while TCRαβ disruption prevented allo-reactivity. In MLCs, CAR38 expression enabled potent ‘allo-defense’ activity against CD38 + allo-reactive cells. Multiplex-base-edited CAR38-T cells exhibited antigen-specific anti-leukemic activity against human B, T, and myeloid malignancies and inhibited disease progression in humanised murine xenograft models. CAR38-T cells offer a potent ‘off-the-shelf’ strategy against CD38 + haematological malignancies and plasma cells associated with autoimmunity.

SUMMARY Inherited mutations in VPS35 and the kinase LRRK2 lead to hyperphosphorylation of Rab GTPases and promote the formation of phospho-Rab signalling complexes. A subset of RH2 domain-containing proteins from the RILP-homology family, including RILP, RILPL1, RILPL2, JIP3, and JIP4 are Rab effectors that recognize the LRRK2-phosphorylated switch 2 threonine of phospho-Rab8A and phospho-Rab10. More recently, phospho-Rabs have been found on lysosomal membranes within multi-protein assemblies involving TMEM55B and RILPL1. TMEM55B is a 284-residue lysosomal membrane protein with no homology to known proteins. It comprises a 218-residue cytosolic N-terminal region and two predicted transmembrane α-helices. Residues 80– 160, which face the cytosol, mediate binding to a C-terminal motif of RILPL1, formed after RILPL1 associates with phospho-Rab8A. Here, we report the crystal structures of TMEM55B alone and in complex with a C-terminal RILPL1 peptide, encompassing the TMEM55B interaction region, which we define as the TMEM55B Binding Motif (TBM). The cytosolic domain of TMEM55B adopts a rigid architecture of two tandem RING-like domains, each forming a Zn²⁺-stabilized 40-residue β-sandwich. TBM binding is mediated primarily by backbone hydrogen bonding and anchored by two glutamate residues from RILPL1. These findings support a model in which RILPL1 is recruited to phospho-Rab8A–positive lysosomes prior to TMEM55B engagement. Further co-immunoprecipitation and mutational analyses indicate that TMEM55B forms complexes independently of phospho-Rabs with proteins containing a conserved TBM, like that of RILPL1, including JIP3, JIP4, OCRL, WDR81, and TBC1D9B. Together, these findings uncover previously unrecognized regulatory networks associated with TMEM55B and lysosomal function and suggest that TMEM55B serves as a central hub for adaptor recruitment at the lysosomal membrane.

Friedreich ataxia (FRDA) is a progressive neuromuscular degenerative disorder caused by GAA repeat expansions in the FXN gene, leading to frataxin deficiency and multisystem pathology. Cardiomyopathy is the leading cause of mortality in individuals with FRDA. To investigate the cellular and molecular mechanisms underlying FRDA-associated cardiac dysfunction, we employed induced pluripotent stem cell (iPSC) lines derived from three individuals with FRDA, each paired with an isogenic control line generated through CRISPR/Cas9-mediated excision of the pathogenic GAA repeat expansion. Correction of the mutation restored FXN expression to levels comparable to healthy donor iPSCs, and all lines differentiated efficiently into cardiomyocytes. Functional analysis revealed significant contractile abnormalities in FRDA cardiomyocytes and multicellular cardiac microtissues, including prolonged contraction and relaxation times and faster beating rates, consistent with clinical observations of cardiac contractile dysfunction. FRDA cardiomyocytes also exhibited pathological features such as increased cell size, irregular calcium transients, elevated mitochondrial reactive oxygen species levels, increased mitochondrial fission and increased cell death. These phenotypes were exacerbated by pathological levels of iron supplementation in culture media, highlighting the heightened sensitivity of frataxin-deficient cardiomyocytes to iron-induced metabolic stress. RNA sequencing revealed a distinct transcriptional profile associated with frataxin deficiency. MEG3 and PCDHGA10 were consistently dysregulated across all three FRDA-iPSC lines and may represent early molecular markers of FRDA cardiomyopathy. Together, these findings establish a robust human iPSC model of FRDA cardiomyopathy that captures early disease phenotypes and reveals novel molecular targets. This preclinical human model provides valuable insight into the pathogenesis of FRDA and provides a platform for developing early-stage therapeutic interventions.

The alternative splicing of the adapter protein NUMB is dysregulated in multiple cancer types, regulating its functional divergence towards either tumor suppression or oncogenesis in an isoform dependant manner. Here we utilized a NUMB exon 9 (E9) splicing reporter in a genome-wide CRISPR screen to identify splicing regulators SRRM1 and SRSF11 that promote NUMB oncogenic splicing in colorectal, lung and breast cancer cell lines. Furthermore, SRRM1 and SRSF11 share common protein interactors, RNA targets and effects on an oncogenic splicing program which favors the expression of pro-tumorigenic isoforms. In addition to NUMB E9, SRRM1 regulates oncogenic splicing events in genes encoding signaling proteins, transcription factors and actin cytoskeleton regulators, many of which also undergo developmentally regulated splicing, including CD44, MKNK2, ECT2, DIAPH1, KAT5, TCF7L2, FOXM1 and TBX3,. Loss of SRRM1 in colon cancer cells reduces cell proliferation and colony formation capabilities as well as expression of tumour promoters Cyclin D1, Notum, and PRDX2. Our data indicate that SRRM1 regulation of alternative splicing represents a node to target multiple properties of malignant cells, with broad effects on cellular signaling, proliferation, EMT, apoptosis resistance and stemness.

Induced pluripotent stem cell (iPSC)-derived natural killer (iNK) cells offer a promising platform for off-the-shelf immunotherapy against hematological malignancies. NK cell function is dynamically regulated through education driven by inhibitory receptors, including CD94/NKG2A and killer cell immunoglobulin-like receptors (KIR). However, the acquisition of inhibitory receptors in iNK cells and their role during differentiation and education remains poorly defined. In this study, we monitored receptor repertoires, transcriptional states, and functional responses in a range of genetically engineered iNK cell lines. Transcriptional reference mapping placed iNK cells close to cytokine-activated NKG2A+ CD56dim peripheral blood (PB) NK cells. Despite their early differentiation stage, iNK cells displayed a well-developed cytotoxic effector program, which was also reflected in high protein expression of Eomes, granzyme B, and activating receptors DNAM-1 and NKG2D. Acquisition of NKG2A by iNK cells was associated with a more differentiated transcriptional state and superior functional responses against a broad range of targets, including those expressing low to moderate levels of HLA-E, suggesting attenuated inhibitory signaling through NKG2A in iNKs. CRISPR knockout of B2-microglobulin (B2M) in iNK cells revealed that the functional potency of NKG2A+ iNK cells was independent of educating interactions with HLA-E in cis or trans. Finally, CRISPR-mediated ablation of NKG2A led to a spontaneous compensatory surface expression of CD94/NKG2C heterodimers, associated with enhanced IFN-g production and cytotoxic activity against target cells with forced high expression of single-chain B2m-HLA-E-peptide trimers. Our results indicate an education-independent functional maturation of iNK cells, characterized by potent effector programs coupled with a favorable early-stage transcriptional profile.

ABSTRACT Pumilio (PUM) RNA binding proteins are crucial for regulating gene expression by binding to a conserved motif in the 3′-untranslated region (3′-UTR). Despite their importance, the role of PUM in plants is largely unexplored. Here, we investigated the functions of Arabidopsis group I PUMs (APUM1-APUM6), which are ubiquitously expressed and localized in the cytosol. While single apum mutants exhibit no visible phenotypes, CRISPR/Cas9-generated apum1 apum2 apum3 triple mutants ( apum1/2/3 ) display reduced growth in both vegetative and reproductive organs, alongside hypersensitivity to various stresses. Remarkably, apum1/2/3/4 quadruple mutants are embryonically lethal, highlighting their essential role in embryo development. Transcriptomic profiling revealed that differentially expressed genes (DEGs) upregulated in apum1/2/3 are enriched in pathways related to photosynthesis, stress responses and anthocyanin biosynthesis, while downregulated DEGs are associated with biotic stress defense and hydrogen peroxide metabolism. This suggests that APUM1/2/3 act as molecular hubs balancing plant growth and stress adaptation. Biochemical assays showed that recombinant APUM homologous domains bind to the 5’-UG U GUAUA-3’ core motif in the 3’-UTR of the transcription factor Production of Anthocyanin Pigment1 (PAP1), crucial for anthocyanin biosynthesis. Notably, single nucleotide substitutions, except for the third U, do not affect binding, while multiple mutations disrupt interaction. Consistently, apum1/2/3 mutants accumulate significantly more anthocyanin than wild-type plants. Furthermore, we predicted 7053 potential target genes for APUM1/2/3, with 1609 present among the upregulated DEGs in apum1/2/3 . Taken together, our findings demonstrate that group I APUMs are vital posttranscriptional regulators, providing a new perspective on the trade-offs between growth and stress resilience in plants.

Internal ribosome entry sites (IRESs) enable cap-independent initiation of picornaviral RNA translation and, together with canonical translation initiation factors, typically require specific cellular proteins known as IRES trans -acting factors (ITAFs). While the type II IRES of foot-and-mouth disease virus (FMDV, an aphthovirus) has been shown to depend on the oncoprotein ITAF45, also known as Proliferation-Associated 2G4 (PA2G4) or ErbB-3 receptor Binding Protein (EBP1), for in vitro assembly of the 48S pre-initiation complex, some related type II IRESs, such as that of encephalomyocarditis virus (EMCV, a cardiovirus), can form the initiation complex independently of ITAF45. In this study, we performed a genome-wide CRISPR screen and identified knockouts of PA2G4 / EBP1 / ITAF45 in cells that survive EMCV infection, suggesting an important role for this factor. We show that the p48 isoform of ITAF45, but not the p42 isoform, is crucial for efficient EMCV/Mengovirus replication and for propagation of replicons in human cell culture. Loss of ITAF45 markedly diminishes EMCV and FMDV IRES activities, which can be rescued by re-expression of ITAF45-p48. Interestingly, cell-free translation assays reveal that EMCV IRES activity is less ITAF45-dependent in vitro , in contrast to FMDV, raising questions about the versatile functions of ITAFs in IRES-driven translation. These findings reveal an isoform-specific function of ITAF45 in supporting cardiovirus infection and provide new insights into the complex regulation of IRES-driven translation, with implications for developing targeted antiviral strategies.

Mutations in the SOD1 gene are among the most significant genetic contributors to amyotrophic lateral sclerosis (ALS), with different variants linked to varying disease severity. To investigate the molecular mechanisms driving this variability, we conducted RNA sequencing on spinal motor neurons (MNs) differentiated from isogenic human induced pluripotent stem cell (iPSC) lines engineered via CRISPR/Cas9. These lines carried two representative SOD1 heterogenous mutations, D91A and G94A, and were analyzed at Days 10 and 20 of neuronal maturation stage to capture the temporal changes of gene expression. We aim to explore how these mutations affect MN function, identify distinct molecular pathways that may explain the variable severity of ALS, and investigate the role of translation and metabolic dysregulation in disease progression.

Genes that enhance T cell function represent promising targets for improving engineered T cell therapies for cancer. While extensive CRISPR knockout screens have identified key genes enhancing T cell persistence, employing Sleeping Beauty ( SB ) insertional mutagenesis, which induces both gain-(GOF) and loss-of-function (LOF) mutations via the generation of fusion transcripts with endogenous genes, may uncover additional critical factors that previous approaches have overlooked. We developed transgenic mice carrying D oxycycline (Dox)-inducible SB mutag e nesis s y stem (DiSBey) in primary T cells. Using DiSBey, we conducted screens for genetic alterations enhancing T cell persistence under chronic antigen exposure. Specifically, CD8⁺ T cells from Dox-fed DiSBey mice were subjected to repeated anti-CD3 stimulation over 18 days to mimic chronic antigenic stimulation. We then identified SB transposon genomic insertion sites and corresponding fusion transcripts from the persistent DiSBey CD8⁺ T cells using enhanced-specificity tagmentation sequencing (esTag-seq) and RNA-seq, respectively. Under chronic stimulation, SB -mutagenized CD8⁺ T cells exhibited improved persistence and reduced terminal exhaustion phenotype. Across six independent screens, we identified 38 genes that were recurrently targeted by the SB transposon T2/Onc2 and differentially expressed under chronic anti-CD3 stimulation stress. Among these, T2/Onc2 insertions into Bach2 and Elmo1 were repeatedly found at the genomic level and were associated with altered nascent transcript expression. Bach2 , known as a key regulator of T cell memory formation and resistance to chronic viral infection but less characterized in engineered T cells for cancer therapy, was found to enhance in vivo tumor persistence in the B16-Ova tumor model. We showed that ectopic Bach2 expression levels influence engineered T cell differentiation lineage. A Bach2 low signature allowed differentiation into both KLRG1⁺ and CD62L⁺ phenotypes, whereas Bach2 high restricted differentiation predominantly to the CD62L⁺ subset. Finally, in human CART19-28ζ cells, BACH2 overexpression enhanced cytotoxicity and improved tumor control following chronic cancer stimulation. Controllable SB mutagenesis using DiSBey mice provides a novel platform for functional screening of genes that improve T cell therapeutic phenotypes. Our findings highlight a dose-dependent role of BACH2 in enhancing the function of engineered T cells under conditions of chronic antigenic stimulation.

Abstract Isoleucine, an essential branched-chain amino acid with broad applications in food, pharmaceuticals, and feed, is predominantly produced via the microbial threonine pathway, which suffers from catalytic complexity and regulatory inefficiency. The propionate pathway offers a streamlined alternative but remains unexplored for L-isoleucine biosynthesis. Here, we engineered Escherichia coli to establish the first propionate pathway-based L-isoleucine cell factory. Critical enzymes—propionyl-CoA synthase (PCS), propionyl-CoA transferase (PCT), and α-ketobutyrate synthase (OBS)—were identified for converting propionate to α-ketobutyrate. Key genes (prpE from Salmonella, pctcp from Gibberella, pctcn from Clostridium propionicum, and nifJ from Moorella thermoacetica) were integrated with the propionate transporter (prpp) and carbonic anhydrase (can) to enhance substrate utilization. ILE-5a, derived from E. coli BW25113 with deletions in brnQ, livJ, and livK, and containing specific insertions, was further modified to create ILE-5b with an additional deletion in yjip. Plasmid-based expression in these strains, ILE-5a and ILE-5b, yielded top producers ILE-5a-P10 and ILE-5b-P10, which achieved L-isoleucine titers of 304 mg/L and 235 mg/L, respectively, in shake-flask fermentation using glucose and propionate as carbon sources. To stabilize production, the optimal gene set (pctcn, nifJ, prpp, can) was genomically integrated via a transposon-encoded CRISPR-Cas system, generating mutants ILE-5a-P11 and ILE-5b-P11. Response surface methodology-optimized medium and 3-L fed-batch fermentation further elevated titers to 1.13 g/L (ILE-5a-P11) and 11.33 g/L (ILE-5b-P11). This study pioneers the propionate pathway for efficient L-isoleucine production, demonstrating its industrial potential through systematic metabolic engineering and process optimization.

Life cycle details or ecological impact are well characterized only for a few ssDNA phages. The Finnlakeviridae family includes one species, Finnlakevirus FLiP . Here, using the same Flavobacterium host and sampling location, we isolated a new strain designated FLiP-2, with 96,7 % genetic identity to the original isolate FLiP. To understand the ecology of this Flavobacterium- infecting phage species, we explored the host interactions of the two FLiP strains and a dsDNA Flavobacterium phage MaF61 under various conditions representing those encountered in their natural habitats in boreal lakes including different temperatures, anoxic conditions, and in the presence of different nutrients and antibiotics. While FLiP and FLiP-2 had similar virion stability outside the host, they exhibited significant differences in plaque morphology and infectivity. FLiP-2 could not replicate in the presence of ampicillin, whereas FLiP thrived even at high concentrations. Both strains of Finnlakevirus FLiP propagated better under or after stress exposure compared to MaF61. Additionally, Finnlakevirus FLiP plaques appeared far from the original infection site, particularly in response to stress, suggesting latent presence within a motile or filamentous bacterium. In conclusion, Finnlakevirus FLiP showed remarkable flexibility in host-interactions being well adapted to fluctuating conditions in boreal freshwaters.