Biology subjects

Venkataramani, V.

Publications and source records attributed to Venkataramani, V..

At least 19 recordsLinked to original sources

bioRxiv2026

The Tensile Expansion Microscopy (TExM) cell stretcher: an iris expansion device integrated with automated real-time autofocus and tracking to super-resolve cells

Mechanical stretchers are used to physically expand biological samples for microscopic studies of mechanobiology. Existing stretchers suffer from limited strain capacity and non-quantifiable forces, along with focus drift and feature-tracking limitations during microscopy. We develop an iris-based cell stretcher that applies isotropic equibiaxial force to achieve aerial strain of 1664% that corresponds to 4.2x linear expansion for Tensile Expansion Microscopy (TExM), a super-resolution method which increases sample size above the diffraction limit of light. The TExM stretcher uses 3D-printed, printed circuit board (PCB) and cost-effective parts, is portable and automated. We verify the performance of the TExM cell stretcher using image analysis, achieving ~90% mechanical precision, a maximum of four degrees of arm angular deviation, precise speed control down to 0.01 cm/sec, and an average expansion resolution of 3.98 x 10^-3 x. Integrated strain gauge sensors confirm equal application of force by each arm of the stretcher throughout expansion and finite-element simulation and planar-polariscope photoelastic imaging characterize the uniform substrate stress distribution while indicating high stress at the substrate gripping area. An AutoTracking software in communication with the stretcher hardware and microscope enables continuous autofocus and feature tracking during TExM and fiducial markers verify uniform equibiaxial stretch. The stretcher is demonstrated with fixed NIH 3T3 fibroblasts and live HeLa cells, observing ~4x cellular expansion of fixed cell size and separation of live cell clusters, highlighting the potential of TExM cell stretcher for biological imaging.

biophysics↗

bioRxiv2026

Tensile Expansion Mass Spectrometry for single cell metabolomics imaging

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) enables the spatial mapping of endogenous biomolecules within native biological specimens; however, it remains limited in achieving single-cell resolution. While advances in instrument modifications, computational processing methods, and tissue-based sample preparation have facilitated high lateral resolutions and cellular level imaging, resolving metabolic heterogeneity at the single-cell level remains challenging for users without specific expertise or custom instrumentation. Here, we present tensile expansion mass spectrometry (TExMS), a cost-effective approach for single-cell MALDI-MSI that is compatible with commercial MSI instrumentation. TExMS utilizes highly stretchable hydrogels as a substrate for live-cell seeding, attachment, and desiccation, avoiding the need for chemical fixation and enabling the retention of both intracellular and extracellular metabolites, including media-derived components that are lost during fixation and washing. We used TExMS to expand individual cells of a human high-grade serous ovarian cancer (HGSOC) cell line and spatially map their small molecule (<800 Da) production. TExMS enabled [~]4-fold linear expansion of the hydrogel, translating to a [~]1.7-fold increase in average cell area and [~]1.3-fold increase in nuclear area and resulting in improved lateral resolution of metabolite distributions. Benchmarking against other platforms for high resolution MALDI-MSI, TExMS offered comparable spatial resolution to microgrid-enabled MALDI-MSI with 15 to 20-fold shorter acquisition times. We then used TExMS to map numerous intermediates from glycolysis, the tricarboxylic acid (TCA) cycle, and amino acid biosynthesis and probe the effects of serum starvation conditions on metabolic flux through these pathways, demonstrating a powerful use case for single-cell MALDI-MSI through TExMS. Table of Contents (TOC) O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/745024v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@18f8c09org.highwire.dtl.DTLVardef@132bc4aorg.highwire.dtl.DTLVardef@1e7c2caorg.highwire.dtl.DTLVardef@a586cf_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2026

Collective cancer cell calcium activity drives brain metastasis

Communication in multicellular networks is a cancer-intrinsic neural feature and crucial for primary brain tumor growth and resistance, but it is unclear whether brain metastases (BrM), the most common and deadliest brain malignancy, are also driven by communicating cancer networks. Using intravital two-photon microscopy in awake mice, clinical specimens, and Ca2+ integrators, we demonstrate that brain-colonizing breast and lung cancer and melanoma cells display gap-junction-dependent, coordinated Ca2+ activity in multicellular, cancer-cell intrinsic networks, which drives their proliferation. Mechanistically, Ca2+ oscillations induce transcription of immediate early genes, adoption of a neuronal expression profile, and cell cycle progression. While many of those features are enriched in BrM, all investigated cancer cell lines showed collective Ca2+ activity. Therapeutically, blocking Ca2+ activity with gap junction inhibitors reduces BrM burden in mouse models. Here we show communicating cancer cell syncytia as drivers of BrM growth, pointing to a targetable pathomechanism, and potentially a new pan-cancer hallmark. Graphical AbstractIn brief Brain metastases form gap-junction-coupled networks exhibiting spontaneous, coordinated Ca2+ activity linked to immediate early gene activation, neuronal gene programs, and cell cycle progression. Disrupting Ca2+ network communication with gap junction inhibitors induces cell cycle arrest and reduces brain metastatic burden in vivo. O_FIG O_LINKSMALLFIG WIDTH=195 HEIGHT=200 SRC="FIGDIR/small/723715v1_ufig1.gif" ALT="Figure 1"> View larger version (88K): org.highwire.dtl.DTLVardef@1130ea0org.highwire.dtl.DTLVardef@254dcdorg.highwire.dtl.DTLVardef@117021forg.highwire.dtl.DTLVardef@18c4f1e_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIBrain metastases display collective Ca2+ activity in gap-junction-coupled networks C_LIO_LICa2+ co-activity is conserved across cancers but enriched in brain metastasis C_LIO_LICa2+ oscillations robustly induce neuronal gene programs and cell cycle progression C_LIO_LIGap junction inhibition reduces brain metastasis burden in mice C_LI

cancer biology↗

bioRxiv2026

Local translation drives glioblastoma heterogeneity and tumor invasion

O_FIG O_LINKSMALLFIG WIDTH=174 HEIGHT=200 SRC="FIGDIR/small/722387v1_ufig1.gif" ALT="Figure 1"> View larger version (96K): org.highwire.dtl.DTLVardef@1da020corg.highwire.dtl.DTLVardef@1bc9b32org.highwire.dtl.DTLVardef@171198aorg.highwire.dtl.DTLVardef@43ce6f_HPS_FORMAT_FIGEXP M_FIG C_FIG Glioblastoma is characterized by diffuse brain invasion, yet the subcellular mechanisms enabling this aggressive behavior remain poorly understood. A subpopulation of glioblastoma cells forms invasive tumor microtubes (TMs), neurite-like extensions that drive whole-brain colonization. Here, we establish local protein translation as a fundamental driver of TM dynamics and invasive cell states. Developing a subcellular transcriptomics approach - integrating subcellular organelle organization with spatially resolved transcriptomics and functional readouts - we reveal that TM gene expression drives cell state identity. Invasive cells further exhibit significantly elevated local translation in protruding TMs, directly linking subcellular protein synthesis to functional invasive states associated with neurodevelopmental programs of axonal growth cones. Targeted disruption of TM-localized translation via photoswitchable puromycin, and specific knockdowns of the TM-enriched proteins GPM6A and GAP43, impaired TM dynamics, suppressed invasion, and reduced tumor growth. Together, these findings define local translation as a key determinant of tumor heterogeneity and glioblastoma invasion.

cancer biology↗

bioRxiv2026

Tensile Expansion Microscopy Applies Mechanical Force to Super-resolve Fixed and Image Live Cellular Samples

Understanding biophysical phenomena requires techniques that access biologically relevant spatial and temporal scales. Expansion Microscopy (ExM) is a sample preparation approach which achieves super-resolution spatial scales by leveraging osmotic forces in a swellable hydrogel to physically separate structures to distances larger than the diffraction limit of light. Yet, in traditional osmotic ExM only pre- and post- expanded samples can be imaged. Further, fragmentation, hydrogel deformation, and signal loss are common while requiring samples to be chemically fixed. Therefore, there is little control of the expansion, reproducibility can be challenging, and dynamics of biological samples at applicable temporal scales cannot be observed. Here, we develop Tensile Expansion Microscopy (TExM) to mechanically expand fixed and, notably, living cellular samples. Highly-stretchable and tough double network alginate- Ca2+/polyacrylamide hydrogels are expanded by tensile forces applied using an electromechanical iris expansion device during continuous imaging on a fluorescence microscope. We incorporate two-photon polymerized microscale fluorescent fiducial markers to track samples and distortion during expansion. The hydrogels controllably and repeatedly expand up to 3.3x with distortions less than 12 {micro}m across 1.3 mm2. TExM is first applied to fixed NIH 3T3 fibroblast cells with immunohistochemistry-stained microtubules, achieving super-resolutions of 100 nm. Then, TExM is demonstrated with living HeLa cells with internal fluorescent reporters showing increased cell size and cell-to-cell separation under 3.2x linear expansion. Overall, TExM allows for continuous, stepwise, and precise temporal modulation of lateral substrate strain, enabling real time monitoring of dynamics of both fixed and viable live cell processes at higher spatial resolutions. TExM can further investigate broad biophysical questions due to its compatibility with other analytical imaging methods that are sensitive to water or fixatives used in traditional osmotic ExM.

biophysics↗

bioRxiv2026

Systematic functional drug testing in patient-derived models reveals ex vivo sensitivities associated with clinical outcome in rare solid tumors

Rare cancers are individually uncommon but collectively represent a substantial share of cancer burden, with limited systemic treatment options for many entities. Molecular profiling identifies targetable alterations, but actionable findings are limited and responses can vary despite a matched target. This motivates complementary approaches that directly assess tumor drug response. Here, we establish a biopsy-compatible ex vivo drug sensitivity testing platform optimized for low input and reproducibility. Patient-derived material was tested either directly or following ex vivo expansion. Functional profiling was performed within clinically relevant timelines across models from 126 patients with rare advanced solid tumors. Drug responses were consistent between model types. In most samples, we identified at least one potentially active compound, supporting feasibility at biopsy-scale. High in vitro sensitivity was associated with clinical benefit and progression-free survival. These findings support functional drug sensitivity testing as a complementary component in precision oncology for adults with rare cancers. Statement of SignificanceThis study presents a biopsy-compatible drug sensitivity testing platform for phenotype-based therapy stratification in rare cancers. It identifies actionable ex vivo drug responses and shows associations with clinical outcome in patients treated with screened therapies. These findings support functional testing as a complementary additional layer of stratification for therapeutic prioritization.

cancer biology↗

bioRxiv2025

Voxel-accurate MRI-microscopy correlation enables AI-powered prediction of brain disease states

Magnetic resonance imaging (MRI) is essential for visualizing the healthy and diseased brain, yet the cellular basis of MRI signal and how it changes over time remain poorly understood. Here, we present BRIDGE (Brain Radiological Imaging with Deep-learning based Ground-Truth Exploration), a platform integrating in vivo MRI with in vivo two-photon (2P) and ex vivo super-resolution microscopy using a multi-step, iterative co-registration pipeline. It enables in vivo, longitudinal, and voxel-precise mapping of MRI signals to their cellular origins for the first time. The registered overlay reveals the cellular and anatomical origins of MRI signals and enables training of convolutional neural networks to enhance the effective resolution of MRI. Using BRIDGE, we identified a microenvironmental vessel biomarker for early metastatic colonization in patient-derived xenograft models of brain metastasis. In particular we found that distinct T2*-weighted hypointense lesions correspond to reduced blood flow and erythrostasis in perimetastatic capillaries. In glioma, longitudinal intravital studies further demonstrated direct correlations between non-vasogenic T2-weighted signal changes and patient-dependent tumor growth dynamics. Taken together, BRIDGE advances radiological interpretation by establishing a microscopic ground truth for MRI signatures over time, enabling deep learning-based predictive histology, and providing cellular-level insights into tumor microenvironment features with direct clinical imaging implications. Graphical abstractBRIDGE enables longitudinal voxel-to-voxel correlation and ground truth based automatic segmentation of MR images O_FIG O_LINKSMALLFIG WIDTH=177 HEIGHT=200 SRC="FIGDIR/small/680637v1_ufig1.gif" ALT="Figure 1"> View larger version (73K): org.highwire.dtl.DTLVardef@f1f64eorg.highwire.dtl.DTLVardef@1619e3eorg.highwire.dtl.DTLVardef@1dc2e7forg.highwire.dtl.DTLVardef@7097e1_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

IRP1 deficiency alters mitochondrial metabolism and protects against metabolic syndrome pathologies

Iron regulatory protein 1 (IRP1) is a post-transcriptional regulator of cellular iron metabolism. In mice, loss of IRP1 causes polycythemia through translational de-repression of hypoxia-inducible factor 2 (HIF2) mRNA, which increases renal erythropoietin production. Here we show that Irp1-/- mice develop fasting hypoglycemia and are protected against high-fat diet-induced hyperglycemia and hepatic steatosis. Discovery-based proteomics of Irp1-/- livers revealed a mitochondrial dysfunction signature. Seahorse flux analysis in primary hepatocytes and differentiated skeletal muscle myotubes confirmed impaired respiratory capacity, with a shift from oxidative phosphorylation to glycolytic ATP production. This metabolic rewiring was associated with enhanced insulin sensitivity and increased glucose uptake in skeletal muscle. Under metabolic stress, IRP1 deficiency altered the redox balance of mitochondrial iron, resulting in inefficient energy production and accumulation of amino acids and metabolites in skeletal muscle, rendering them unavailable for hepatic gluconeogenesis. These findings identify IRP1 as a critical regulator of systemic energy homeostasis.

pathology↗

bioRxiv2025

High LET Radiation: A Novel Strategy to Overcome Tumor Microtubes -Mediated Radioresistance in Glioblastoma

PurposeTumor cell networks formed by tumor microtubes (TMs) are thought to drive therapy resistance in glioblastoma (GB). X-ray irradiation enhances TM formation, thereby increasing radioresistance. We hypothesize that high linear energy transfer (LET) particle radiotherapy is less affected by TM-mediated resistance due to its reduced reliance on indirect DNA damage. This study explores the impact of LET-induced DNA damage on TMs formation and GB survival Material and MethodsFormation of TMs was investigated in the primary patient derived glioblastoma stem-like cell lines (S24 and T269) irradiated with different LET, ranging from 3 - 107 keV/{micro}m, across dose series (1, 2, 4, 6 Gy) of clinical proton, helium, and carbon ion beams. TM networks and DNA damage patterns, specifically {gamma}H2AX foci, were visualized using fluorescence microscopy. Cell survival was evaluated through clonogenic survival assays. ResultsThe formation of TMs, radiation-induced nuclear DNA damage repair foci, and GB cell survival were correlated with a gradual increase in LET. Consistent with conventional photon/X-rays, low-LET proton irradiation promoted TMs formation in a dose-dependent manner. In contrast, an anti-correlation between LET and TMs induction was found, i.e., a decreased network connectivity with gradual increase of LET and formation of complex DNA damage. Consequently, LET increase correlated with reduced cell survival, with the most pronounced cell killing observed after high-LET carbon irradiation. Moreover, the inverse correlation between LET and TMs density was further confirmed for a broad range of LET modulated within the carbon ion irradiation. ConclusionThis is the first report on the relevance of LET as a novel mean to overcome TMs network-mediated radioresistance in GB, with ramifications for the clinical translation of high-LET particle radiotherapy to further improve outcome in this still devastating disease.

cancer biology↗

bioRxiv2024

Single-cell multidimensional profiling of tumor cell heterogeneity in supratentorial ependymomas

Supratentorial ependymomas are aggressive childhood brain cancers that retain features of neurodevelopmental cell types and segregate into molecularly and clinically distinct subgroups, suggesting different developmental roots. The developmental signatures as well as microenvironmental factors underlying aberrant cellular transformation and behavior across each supratentorial ependymoma subgroup are unknown. Here we integrated single cell- and spatial transcriptomics, as well as in vitro and in vivo live-cell imaging to define supratentorial ependymoma cell states, spatial organization, and dynamic behavior within the neural microenvironment. We find that individual tumor subgroups harbor two distinct progenitor-like cell states reminiscent of early human brain development and diverge in the extent of neuronal or ependymal differentiation. We further uncover several modes of spatial organization of these tumors, including a high order architecture influenced by mesenchymal and hypoxia signatures. Finally, we identify an unappreciated role for brain-resident cells in shifting supratentorial ependymoma cellular heterogeneity towards neuronal-like cells that co-opt immature neuronal morphology and invasion mechanisms. Collectively, these findings provide a multidimensional framework to integrate transcriptional and phenotypic characterization of tumor heterogeneity in supratentorial ependymoma and its potential clinical implications.

cancer biology↗

bioRxiv2024

Characterizing and targeting glioblastoma neuron-tumor networks with retrograde tracing

Glioblastomas are invasive brain tumors with high therapeutic resistance. Neuron-to-glioma synapses have been shown to promote glioblastoma progression. However, a characterization of tumor-connected neurons has been hampered by a lack of technologies. Here, we adapted retrograde tracing using rabies viruses to investigate and manipulate neuron-tumor networks. Glioblastoma rapidly integrated into neural circuits across the brain engaging in widespread functional communication, with acetylcholinergic neurons driving glioblastoma invasion. We uncovered patient-specific and tumor cell state-dependent differences in synaptogenic gene expression associated with neuron-tumor connectivity and subsequent invasivity. Importantly, radiotherapy enhanced neuron-tumor connectivity by increased neuronal activity. In turn, simultaneous neuronal activity inhibition and radiotherapy showed increased therapeutic effects, indicative of a role for neuron-to-glioma synapses in contributing to therapeutic resistance. Lastly, rabies-mediated genetic ablation of tumor-connected neurons halted glioblastoma progression, offering a viral strategy to tackle glioblastoma. Together, this study provides a framework to comprehensively characterize neuron-tumor networks and target glioblastoma.

cancer biology↗

bioRxiv2024

Direct excitatory synapses between neurons and tumor cells drive brain metastatic seeding of breast cancer and melanoma

Interactions between neurons and cancer cells are found in many malignancies, but their relevance for metastatic organ colonization remain largely unknown. It is also unclear whether any direct synaptic communication between neurons and cancer cells of non-neural tumor types exists, and if so, whether this can support metastasis and thus cancer progression. Here we show that excitatory synapses are formed between neurons and brain-metastatic melanoma and breast cancer cells. This starts at an early microscopic stage after extravasation into the brain parenchyma, during residence of cancer cells in the perivascular niche, a critical step for their survival. These neuron-cancer synapses showed a bona fide synaptic ultrastructure, and generated excitatory postsynaptic currents mediated by glutamate receptors of the AMPA subtype in cancer cells. In accordance, AMPA receptor signatures were consistently detected in preclinical and patient samples of melanoma and breast cancer brain metastases. Genetic perturbation and pharmacological inhibition of AMPA receptors with the approved antiepileptic drug perampanel in models of breast and melanoma cancer reduced the number of brain metastases and overall brain metastatic burden. These findings demonstrate for the first time that neurons can form biologically relevant direct synapses with non-neural cancer cells. In brain metastasis, a particularly challenging complication of many common malignancies, this non-canonical stimulatory synaptic interaction offers novel therapeutic opportunities.

cancer biology↗

bioRxiv2023

Mitochondrial CISD1 is a downstream target that mediates PINK1 and Parkin loss-of-function phenotypes

Parkinsons disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra of the midbrain. Familial cases of PD are often caused by mutations of PTEN-induced kinase 1 (PINK1) and the ubiquitin ligase Parkin, both pivotal in maintaining mitochondrial quality control. CISD1, a homodimeric mitochondrial iron-sulfur-binding protein, is a major target of Parkin-mediated ubiquitination. We here discovered a heightened propensity of CISD1 to form dimers in Pink1 mutant flies and in dopaminergic neurons from PINK1 mutation patients. The dimer consists of two monomers that are covalently linked by a disulfide bridge. In this conformation CISD1 cannot coordinate the iron-sulfur cofactor. Overexpressing Cisd, the Drosophila orthologue of CISD1, and a mutant Cisd incapable of binding the iron-sulfur cluster in Drosophila reduced climbing ability and lifespan. This was more pronounced with mutant Cisd and aggravated in Pink1 mutant flies. Complete loss of Cisd, in contrast, rescued all detrimental effects of Pink1 mutation on climbing ability, wing posture, dopamine levels, lifespan, and mitochondrial ultrastructure. Our results suggest that Cisd, probably iron-depleted Cisd, operates downstream of Pink1 shedding light on PD pathophysiology and implicating CISD1 as a potential therapeutic target.

neuroscience↗

bioRxiv2023

Deep intravital brain tumor imaging enabled by tailored three-photon microscopy and analysis

Intravital two-photon microscopy has emerged as a powerful technology to study brain tumor biology and its temporal dynamics, including invasion, proliferation and therapeutic resistance in the superficial layers of the mouse cortex. However, intravital microscopy of deeper cortical layers and especially the subcortical white matter, an important route of glioblastoma invasion and recurrence, has not yet been feasible due to low signal-to-noise ratios, missing spatiotemporal resolution and the inability to delineate myelinated axonal tracts. Here, we present a tailored intravital microscopy and artificial intelligence-based analysis methodology and workflow that enables routine deep imaging of glioblastoma over extended time periods, named Deep3P. We show that three-photon microscopy, adaptive optics, as well as customized deep learning-based denoising and machine learning segmentation together allow for deep brain intravital investigation of tumor biology up to 1.2 mm depth. Leveraging this approach, we find that perivascular invasion is a preferred invasion route into the corpus callosum as compared to intracortical glioblastoma invasion and uncover two vascular mechanisms of glioblastoma migration in the white matter. Furthermore, we can define an imaging biomarker of white matter disruption during early glioblastoma colonization. Taken together, Deep3P allows for an efficient and non-invasive investigation of brain tumor biology and its tumor microenvironment in unprecedented deep white and gray matter of the living mouse, opening up novel opportunities for studying the neuroscience of brain tumors and other model systems.

cancer biology↗

bioRxiv2021

A connectivity signature for glioblastoma

Tumor cell extensions called tumor microtubes (TMs) in glioma resemble neurites during neurodevelopment and connect glioma cells to a network that has considerable relevance for tumor progression and therapy resistance. The determination of interconnectivity in individual tumors has been challenging and the impact of tumor cell connectivity on patient survival remained unresolved so far. Here, a connectivity signature from single-cell RNA-sequenced (scRNA-Seq) xenografted primary glioblastoma (GB) cells was established and clinically validated. Thirty-four of 40 connectivity genes were related to neurogenesis, neural tube development or glioma progression, including the TM-network-relevant GAP43 gene. Astrocytic-like and mesenchymal-like GB cells had the highest connectivity signature scores in scRNA-Seq data of patient-derived xenografts and patient samples. In 230 human GBs, high connectivity correlated with the mesenchymal expression subtype, TP53 wildtype, and with dismal patient survival. CHI3L1 was identified as a robust molecular marker of connectivity. Thus, the connectivity signature allows novel insights into brain tumor biology, provides a proof-of-principle that tumor cell connectivity is relevant for patients prognosis, and serves as a robust biomarker that can be used for future clinical trials. Statement of significanceIntegration of GB cells into functional networks drives tumor progression and resistance. Here, we established and validated a novel connectivity gene expression signature of single GB cells and whole tumors that can be easily applied to clinical and preclinical samples. It is shown that connectivity is determining prognosis combining molecular, functional and clinical insights into the disease.

cancer biology↗

bioRxiv2021

Coordinate regulation of liver ferroportin degradation and de novo synthesis determines serum iron levels in mice

The iron hormone hepcidin is transcriptionally activated by iron or inflammation via distinct, partially overlapping pathways. We addressed how iron affects inflammatory hepcidin levels and the ensuing hypoferremic response. Dietary iron overload did not mitigate hepcidin induction in LPS-treated wt mice but prevented effective inflammatory hypoferremia. Likewise, LPS modestly decreased serum iron in hepcidin-deficient Hjv-/-mice, model of hemochromatosis. Synthetic hepcidin triggered hypoferremia in control but not iron-loaded wt animals. Furthermore, it dramatically decreased hepatic and splenic ferroportin in Hjv-/-mice on standard or iron-deficient diet, but only triggered hypoferremia in the latter. Mechanistically, iron antagonized hepcidin responsiveness by inactivating IRPs in the liver and spleen, to stimulate ferroportin mRNA translation. Prolonged LPS treatment eliminating ferroportin mRNA permitted hepcidin-mediated hypoferremia in iron-loaded mice. Thus, de novo ferroportin synthesis is critical determinant of serum iron and finetunes hepcidin-dependent functional outcomes. Our data uncover a crosstalk between hepcidin and IRE/IRP systems that controls tissue ferroportin expression and determines serum iron levels. Moreover, they suggest that hepcidin supplementation therapy is more efficient combined with iron depletion.

immunology↗

bioRxiv2021

Mucoricin is a Ricin-Like Toxin that is Critical for the Pathogenesis of Mucormycosis

Fungi of the order Mucorales cause mucormycosis, a lethal infection with an incompletely understood pathogenesis. We now demonstrate that Mucorales fungi produce a toxin that plays a central role in virulence. Polyclonal antibodies against this toxin inhibit its ability to damage human cells in vitro, and prevent hypovolemic shock, organ necrosis, and death in mice with mucormycosis. RNAi inhibition of the toxin in Rhizopus delemar, compromises the ability of the fungus to damage host cells and attenuates virulence in mice. This 17 kDa toxin has structural and functional features of the plant toxin, ricin, including the ability to inhibit protein synthesis by its N-glycosylase activity, the existence of a motif that mediates vascular leak, and a lectin sequence. Antibodies against the toxin inhibit R. delemar- or toxin-mediated vascular permeability in vitro and cross-react with ricin. A monoclonal anti-ricin B chain antibody binds to the toxin and also inhibits its ability to cause vascular permeability. Therefore, we propose the name "mucoricin" for this toxin. Not only is mucoricin important in the pathogenesis of mucormycosis but our data suggest that a ricin- like toxin is produced by organisms beyond the plant and bacterial kingdoms. Importantly, mucoricin should be a promising therapeutic target.

microbiology↗

bioRxiv2020

MLX balances metabolism and stress to suppress apoptosis and maintain spermatogenesis

Male germ cell production is a metabolically-driven and apoptosis-prone process. Here we show that the glucose-sensing transcription factor MLX, and its binding partner MondoA, are both required for male fertility in the mouse, as well as survival of human tumor cells derived from the male germ line. Loss of Mlx results in altered metabolism as well as activation of multiple stress pathways and germ cell apoptosis in the testes. This is concomitant with dysregulation of the expression of male-specific germ cell transcripts and proteins, manifesting as oligoasthenoteratozoospermia (OAT). Our genomic and functional analyses identify loci directly bound by MLX involved in these processes, including metabolic targets, apoptotic effectors and obligate components of male-specific germ cell development. These in vivo and in vitro studies implicate MLX and other members of the proximal MYC network, such as MNT, in regulation of metabolism and differentiation, as well as in suppression of intrinsic and extrinsic death signaling pathways in both spermatogenesis and male germ cell tumors. Highlights- The MAX-like bHLHLZ protein MLX is required for male fertility, but not embryonic development. - MLX and its heterodimeric partner MondoA are each required for both male fertility and survival of male germ cell tumors. - Genomic analysis identifies direct MLX targets associated with metabolism, stress and male germ cell development. - Loss of MLX alters MYC network genome occupancy and transcriptional output.

developmental biology↗