Biology subjects

Zaidi, M.

Publications and source records attributed to Zaidi, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Linezolid Acts as a Selective Inhibitor of the JAK2V617F Mutation

The JAK2V617F (JAK2VF) driver mutation is found in 95% of patients with polycythemia vera (PV), a progressive myeloproliferative neoplasm. Current treatments suppress excessive hematopoiesis but lack specificity for targeting JAK2VF cells, are unable to deplete mutant stem/progenitor cells and ultimately result in drug resistance. We discovered that the FDA-approved antibiotic, linezolid (LZD), ameliorates the PV phenotype across multiple model systems. LZD suppressed cell proliferation and STAT5 signaling, altered the cell cycle, and increased apoptosis of JAK2VF-harboring human erythroleukemia cells, but not in wild-type acute leukemia cells. Computational modelling indicated that LZD interacts specifically with mutant JAK2VF but not with wild-type JAK2 protein. We further showed that, in JAK2VF mice that faithfully recapitulate human PV, LZD mitigates disease burden by selectively targeting JAK2VF stem cells thereby normalizing spleen size and blood counts. LZD also inhibited hematopoietic colony formation by patient-derived peripheral blood mononuclear cells, with the more primitive progenitors being preferred targets. Importantly, LZD selectively decreased JAK2VF+ colony numbers, without impacting wild-type JAK2 colonies. In all, the data provide a firm foundation for evaluating LZD-like molecules as an effective therapy for PV and other myeloproliferative neoplasms. Key pointsO_LILinezolid acts as a JAK2V617FIZselective inhibitor in PV mouse models and PV patient samples while sparing wildIZtype hematopoiesis. C_LIO_LILinezolid acts directly on JAK2V617F hematopoietic stem cells. C_LI

cancer biology↗

bioRxiv2026

Erythroferrone Modulates Osteoblast-Osteoclast Crosstalk During Bone Remodeling

Erythroferrone (ERFE) secretion inhibits hepcidin expression by sequestering several bone morphogenetic protein (BMP) family members to increase iron availability for erythropoiesis. Recent evidence demonstrates that ERFE is also expressed in osteoblasts and osteoclasts and Erfe-/- mice display low-bone-mass arising from increased bone resorption despite a concomitant increase in bone formation. To mechanistically dissect how bone-derived ERFE exerts an osteoprotective effect, we first created Erfefl/fl mice, which were then crossed with Col2.3-Cre mice to generate osteoblast-selective Erfe mutants (or Erfefl/fl;Col2.3-Cre mice). We now demonstrate that ERFE derived from osteoblasts is not responsible for the decreased BMD noted in Erfe-/- mice, revealing enhanced BMD during anabolic stress in Erfefl/fl;Col2.3-Cre mice. Consistently, in contrast to global ERFE loss, osteoblast-selective ERFE loss does not increase osteoclasts in vivo. Furthermore, our results demonstrate that ERFE loss in osteoblasts induces osteoclast Erfe expression in co-culture experiments in vitro. Finally, the osteoclastogenesis gene program is induced in co-culture with osteoblasts only when ERFE is lost in osteoclasts. Taken together, our finding provide strong evidence of osteoclast-derived ERFE as a central osteoprotective regulator of bone mass, its loss resulting in net bone loss in Erfe-/- mice. BRIEF SUMMARYLoss of erythroferrone derived from osteoclasts enhances osteoclastogenesis resulting in accelerated bone loss. SIGNIFICANCE STATEMENTCanonical erythroferrone (ERFE) function includes hepcidin suppression through bone morphogenic proteins (BMPs) sequestration, establishing the rationale for ERFE-mediated regulation of bone homeostasis. We previously showed that global ERFE loss controls bone mass. Here, we report that osteoclast-derived ERFE is a major regulator of osteoclastogenesis. For this, we crossed Erfefl/fl with Col2.3-Cre mice to generate osteoblast-selective Erfe mutants, demonstrating that osteoblast-derived ERFE does not recapitulate bone loss found in global ERFE knockout mice. In contrast, bone mineral density is enhanced during anabolic stress in Erfefl/fl;Col2.3-Cre mice. Finally, we document that osteoclast ERFE loss enhances osteoclastogenesis in co-culture with osteoblasts. Together, the data provide compelling evidence that osteoclast-derived ERFE modulates communication between osteoblasts and osteoclasts.

cell biology↗

bioRxiv2025

Multiplex imaging combined to machine learning enable automated profiling of cortical malformations applications in tuberous sclerosis complex

Malformations of cortical development such as tuberous sclerosis complex arise within a heterogeneous cellular landscape that conventional histopathology only partially resolves. Here, we combined a 19-marker multiplex immunofluorescence panel with a machine learning-driven image analysis pipeline to map and quantify over 365 000 cells from paediatric surgical cortex, defining the single-cell architecture of TSC lesions. Microtubers were objectively delineated by vimentin and detected in all TSC samples but absent from non-dysplastic controls. Within these structures, balloon cells exhibiting strong pS6 activation occupied lesion cores and were confined to microtuber boundaries, whereas dysmorphic neurons were more diffusely distributed into adjacent cortex. The microtuber niche was dominated by astroglial remodeling: immature and reactive vimentin-positive astrocytes, including Lamp5-positive subsets, accumulated at and around lesion rims, while mature GFAP-positive astrocytes showed only modest changes. Distance-based spatial analyses revealed neuronal exclusion from microtuber centres with gradual recovery in surrounding tissue, indicating local network disruption. Unsupervised clustering and niche modelling recapitulated these spatial gradients, identifying a glial-dominated ecosystem that concentrates balloon cells, increases inter-neuronal distances, and reduces cell-cell interactions. Together, these data support a model in which cortical tubers arise through the coalescence of microtubers orchestrated by balloon cells and reactive gliosis during corticogenesis. Beyond elucidating disease architecture, our automated framework enables reproducible lesion detection, quantitative cell-state mapping, and spatial readouts applicable across malformations of cortical development. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC="FIGDIR/small/690101v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@dc3258org.highwire.dtl.DTLVardef@6d4149org.highwire.dtl.DTLVardef@d93354org.highwire.dtl.DTLVardef@1b8f83d_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Enhancing the iNKT cell immunotherapy platform by combining optimised CAR endodomains with novel iNKT engagers

iNKT cells are emerging as a highly promising immunotherapy platform for the treatment of cancer. To maximise the anti-cancer activity of CAR-iNKT against the blood cancer multiple myeloma we investigated optimal CAR designs and their combination with novel iNKT-specific engagers. We find that amongst five different CAR endodomains, underpinned by increased avidity and a cross talk between Plexin D1 on CAR-iNKT and Semaphorin 4A on myeloma cells, BCMA CD28z CAR-iNKT exert the highest anti-myeloma activity. Notably, CD28z CAR-iNKT outperform their CAR-T counterparts. To expand the anti-myeloma potential of CAR-iNKT, we designed and validated a high efficacy BCMA iNKT-specific engager which exerts significant anti-myeloma activity in conjunction with adoptively transferred iNKT cells. Finally, combined, dual target therapy with FCRL5 CAR-iNKT and BCMA iNKT engagers outperforms FCRL5 CAR-iNKT and limits immune escape of FCRL5-negative myeloma. Thus, optimised iNKT-based, dual-target, dual-modality immunotherapy has enhanced anti-tumor activity against multiple myeloma and potentially other malignancies. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=159 SRC="FIGDIR/small/683869v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@11e843corg.highwire.dtl.DTLVardef@7bb408org.highwire.dtl.DTLVardef@1687b84org.highwire.dtl.DTLVardef@8542ea_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

Gender-specific Single Transcript Level Atlas of Vasopressin and its Receptor (AVPR1a) in the Mouse Brain

Vasopressin (AVP), a nonapeptide synthesized predominantly by magnocellular hypothalamic neurons, is conveyed to the posterior pituitary via the pituitary stalk, where AVP is secreted into the circulation. Known to regulate blood pressure and water homeostasis, it also modulates diverse social behaviors, such as pair-bonding, social recognition and cognition in mammals including humans. Importantly, AVP modulates social behaviors in a sex-specific manner, perhaps, due to sex differences in the distribution in the brain of AVP and its main receptor AVPR1a. There is a corpus of integrative studies for the expression of AVP and AVPR1a in various brain regions, and their functions in modulating central and peripheral actions. In order to purposefully address sexually dimorphic and novel roles of AVP on central and peripheral functions through its AVPR1a, we utilized RNAscope to map Avp and Avpr1a single transcript expression in the mouse brain. As the most comprehensive atlas of AVP and AVPR1a in the mouse brain, this compendium highlights the importance of newly identified AVP/AVPR1a neuronal nodes that may stimulate further functional studies.

neuroscience↗

bioRxiv2024

Gene-Dose-Dependent Reduction Fshr Expression Improves Spatial Memory Deficits in Alzheimer's Mice

Alzheimers disease (AD) is a major progressive neurodegenerative disorder of the aging population. High post-menopausal levels of the pituitary gonadotropin follicle-stimulating hormone (FSH) are strongly associated with the onset of AD, and we have shown recently that FSH directly activates the hippocampal Fshr to drive AD-like pathology and memory loss in mice. To establish a role for FSH in memory loss, we used female 3xTg;Fshr+/+, 3xTg;Fshr+/- and 3xTg;Fshr-/- mice that were either left unoperated or underwent sham surgery or ovariectomy at 8 weeks of age. Unoperated and sham-operated 3xTg;Fshr-/-mice were implanted with 17{beta}-estradiol pellets to normalize estradiol levels. Morris Water Maze and Novel Object Recognition behavioral tests were performed to study deficits in spatial and recognition memory, respectively, and to examine the effects of Fshr depletion. 3xTg;Fshr+/+mice displayed impaired spatial memory at 5 months of age; both the acquisition and retrieval of the memory were ameliorated in 3xTg;Fshr-/- mice and, to a lesser extent, in 3xTg;Fshr+/- mice-- thus documenting a clear gene-dose-dependent prevention of hippocampal-dependent spatial memory impairment. At 5 and 10 months, sham-operated 3xTg;Fshr-/- mice showed better memory performance during the acquisition and/or retrieval phases, suggesting that Fshr deletion prevented the progression of spatial memory deficits with age. However, this prevention was not seen when mice were ovariectomized, except in the 10-month-old 3xTg;Fshr-/-mice. In the Novel Object Recognition test performed at 10 months, all groups of mice, except ovariectomized 3xTg;Fshr-/- mice showed a loss of recognition memory. Consistent with the neurobehavioral data, there was a gene-dose-dependent reduction mainly in the amyloid {beta}40 isoform in whole brain extracts. Finally, serum FSH levels <8 ng/mL in 16-month-old APP/PS1 mice were associated with better retrieval of spatial memory. Collectively, the data provide compelling genetic evidence for a protective effect of inhibiting FSH signaling on the progression of spatial and recognition memory deficits in mice, and lay a firm foundation for the use of an FSH-blocking agent for the early prevention of cognitive decline in postmenopausal women.

neuroscience↗

bioRxiv2024

Single Transcript Level Atlas of Oxytocin and the Oxytocin Receptor in the Mouse Brain

Oxytocin (OXT), a primitive nonapeptide known to regulate reproduction and social behaviors, is synthesized primarily in the hypothalamus and is secreted via hypophyseal-portal system of the posterior pituitary gland. Given that pituitary hormones, traditionally thought of as regulators of single targets, display an array of central and peripheral actions, OXT also directly affects bone and body composition. Its effects on bone remodeling are physiologically relevant, as elevated OXT levels during pregnancy and lactation could cause calcium mobilization from the maternal skeleton for intergenerational calcium transfer towards fetal bone growth. There is an equally large body of evidence that has established the presence of OXT receptors (OXTRs) in the brain through which central functions, such as social bonding, and peripheral functions, such as the regulation of body composition, can be exerted. To purposefully address the effects of OXT on the brain, we used RNAscope to map OXT and OXTR expression, at the single transcript level, in the whole mouse brain. Identification of brain nuclei with the highest OXT and OXTR transcript density will shed further light on functional OXT nodes that could be further interrogated experimentally to define new physiologic circuitry.

physiology↗

bioRxiv2024

An Atlas of Brain-Bone Sympathetic Neural Circuits

There is clear evidence that the sympathetic nervous system (SNS) mediates bone metabolism. Histological studies show abundant SNS innervation of the periosteum and bone marrow--these nerves consist of noradrenergic fibers that immunostain for tyrosine hydroxylase, dopamine beta hydroxylase, or neuropeptide Y. Nonetheless, the brain sites that send efferent SNS outflow to bone have not yet been characterized. Using pseudorabies (PRV) viral transneuronal tracing, we report, for the first time, the identification of central SNS outflow sites that innervate bone. We find that the central SNS outflow to bone originates from 87 brain nuclei, sub-nuclei and regions of six brain divisions, namely the midbrain and pons, hypothalamus, hindbrain medulla, forebrain, cerebral cortex, and thalamus. We also find that certain sites, such as the raphe magnus (RMg) of the medulla and periaqueductal gray (PAG) of the midbrain, display greater degrees of PRV152 infection, suggesting that there is considerable site-specific variation in the levels of central SNS outflow to bone. This comprehensive compendium illustrating the central coding and control of SNS efferent signals to bone should allow for a greater understanding of the neural regulation of bone metabolism, and importantly and of clinical relevance, mechanisms for central bone pain.

neuroscience↗

bioRxiv2023

Atlas of Fshr Expression from Novel Reporter Mice

The FSH-FSHR signaling pathway has traditionally been considered an essential regulator in reproductive development and fertility. But there has been emerging evidence of FSHR expression in extragonadal tissues/organs. This poses new questions and long-term debates regarding the physiological role of the FSH-FSHR pathway, and underscores the need for reliable, in vivo analysis of FSHR expression in animal models. However, conventional methods have proven insufficient for examining FSHR expression due to limitations, such as the scarcity of reliable antibodies, rapid turnover/degradation of transcripts, and a lack of robust in vivo tools. To address this challenge, we developed Fshr-ZsGreen knockin reporter mice under the control of Fshr endogenous promoter using CRISPR/Cas9 genome-editing technology to append a P2A-ZsGreen targeting vector into a locus between the last exon and the stop codon of Fshr. With this novel genetic tool, we provide a reliable readout of Fshr expression at single-cell resolution level in vivo and in real time. Reporter animals were also subjected to additional analyses, including immunohistochemical staining, ddRT-PCR, and in situ hybridization, to define the accurate expression profile of FSHR in gonadal and extragonadal organs/tissues. Our compelling results not only demonstrated Fshr expression in intragonadal tissues but also, strikingly, unveiled notably increased expression in Leydig cells, osteoblast lineage cells, endothelial cells in vascular structures, and epithelial cells in bronchi of the lung and renal tubes. The genetic decoding of the widespread pattern of Fshr expression highlights its physiological relevance beyond reproduction and fertility, and opens new avenues for therapeutic options for age-related disorders of the bones, lungs, kidneys, and hearts, among other tissues/organs. Exploiting the power of the Fshr knockin reporter animals, this report provides the first comprehensive genetic record of the spatial distribution of FSHR expression, correcting a long-term misconception about Fshr expression and offering prospects for extensive exploration of FSH-FSHR biology.

cell biology↗

bioRxiv2023

Development and Biophysical Characterization of a Humanized FSH-Blocking Monoclonal Antibody Therapeutic Formulated at an Ultra-High Concentration

Highly concentrated antibody formulations are oftentimes required for subcutaneous, self-administered biologics. Here, we report the creation of a unique formulation for our first-in- class FSH-blocking humanized antibody, MS-Hu6, which we propose to move to the clinic for osteoporosis, obesity, and Alzheimers disease. The studies were carried out using our Good Laboratory Practice (GLP) platform, compliant with the Code of Federal Regulations (Title 21, Part 58). We first used protein thermal shift, size exclusion chromatography, and dynamic light scattering to examine MS-Hu6 concentrations between 1 and 100 mg/mL. We found that thermal, monomeric, and colloidal stability of formulated MS-Hu6 was maintained at a concentration of 100 mg/mL. The addition of the antioxidant L-methionine and chelating agent disodium EDTA improved the formulations long-term colloidal and thermal stability. Thermal stability was further confirmed by Nano differential scanning calorimetry (DSC). Physiochemical properties of formulated MS-Hu6, including viscosity, turbidity, and clarity, conformed with acceptable industry standards. That the structural integrity of MS-Hu6 in formulation was maintained was proven through Circular Dichroism (CD) and Fourier Transform Infrared (FTIR) spectroscopy. Three rapid freeze-thaw cycles at -80{degrees}C/25{degrees}C or -80{degrees}C/37{degrees}C further revealed excellent thermal and colloidal stability. Furthermore, formulated MS-Hu6, particularly its Fab domain, displayed thermal and monomeric storage stability for more than 90 days at 4{degrees}C and 25{degrees}C. Finally, the unfolding temperature (Tm) for formulated MS-Hu6 increased by >4.80{degrees}C upon binding to recombinant FSH, indicating highly specific ligand binding. Overall, we document the feasibility of developing a stable, manufacturable and transportable MS-Hu6 formulation at a ultra-high concentration at industry standards. The study should become a resource for developing biologic formulations in academic medical centers.

bioengineering↗

bioRxiv2022

Brain Atlas for Glycoprotein Hormone Receptors at Single-Transcript Level

There is increasing evidence that anterior pituitary hormones, traditionally thought to have unitary functions in regulating single endocrine targets, act on multiple somatic tissues, such as bone, fat, and liver. There is also emerging evidence for anterior pituitary hormone action on brain receptors in mediating central neural and peripheral somatic functions. Here, we have created the most comprehensive neuroanatomical atlas on the expression of TSHRs, LHCGRs and FSHRs. We have used RNAscope, a technology that allows the detection of mRNA at single-transcript level, together with protein level validation, to document Tshr expression in 173 and Fshr expression in 353 brain regions, nuclei and sub-nuclei identified using the Atlas for the Mouse Brain in Stereotaxic Coordinates. We also identified Lhcgr transcripts in 401 brain regions, nuclei and sub-nuclei. Complementarily, we used ViewRNA, another single-transcript detection technology, to establish the expression of FSHRs in human brain samples, where transcripts were co-localized in MALAT1-positive neurons. In addition, we show high expression for all three receptors in the ventricular region--with yet unknown functions. Intriguingly, Tshr and Fshr expression in the ependymal layer of the third ventricle was similar to that of the thyroid follicular cells and testicular Sertoli cells, respectively. TSHRs were expressed specifically in tanycytes. In contrast, Fshrs were localized to NeuN-positive neurons in the granular layer of the dentate gyrus in murine and human brain--both are Alzheimers disease vulnerable regions. Our atlas thus provides a vital resource for scientists to explore the link between the stimulation or inactivation of brain glycoprotein hormone receptors on somatic function. New actionable pathways for human disease may be unmasked through further studies.

neuroscience↗

bioRxiv2022

Inferring light responses of primate retinal ganglion cells using intrinsic electrical signatures

Reproducing high-acuity vision with an epiretinal implant will likely require inferring the natural light responses of diverse RGC types in the implanted retina, without measuring them directly. Here we demonstrate an approach that exploits intrinsic electrical features of primate RGCs. First, ON-parasol and OFF-parasol RGCs were identified with 95% accuracy using electrical features. Then, the somatic electrical footprint, predicted cell type, and average linear-nonlinear-Poisson model parameters of each cell type were used to infer a light response model for each cell. Across five retinas, these models achieved an average correlation with measured firing rates of 0.49 for white noise visual stimuli and 0.50 for natural scenes stimuli, compared to 0.65 and 0.58 respectively for models fitted to recorded light responses, an upper bound. This finding, and linear decoding of images from predicted RGC activity, suggested that the inference approach may be useful for high-fidelity sight restoration.

neuroscience↗

bioRxiv2022

A Single Multipurpose FSH-Blocking Therapeutic for Osteoporosis and Obesity

Pharmacological and genetic studies over the past decade have established FSH as an actionable target for diseases affecting millions, notably osteoporosis, obesity and Alzheimers disease (AD). Blocking FSH action prevents bone loss, fat gain and AD-like features in mice. We recently developed a first-in-class, humanized, epitope-specific FSH blocking antibody, MS-Hu6, with a KD of 7.52 nM. Using a GLP-compliant platform, we now report the efficacy of MS-Hu6 in preventing obesity and osteoporosis in mice, and parameters of acute safety in monkeys. Biodistribution studies using 89Zr-labelled, biotinylated or unconjugated MS-Hu6 in mice and monkeys showed localization to bone, bone marrow and fat depots. MS-Hu6 displayed a {beta} phase t[1/2] of 13 days (316 hours) in humanized Tg32 mice, and bound endogenous FSH. We tested 215 variations of excipients using the protein thermal shift assay to generate a final formulation that rendered MS-Hu6 stable in solution upon freeze-thaw and at different temperatures, with minimal aggregation, and without self-, cross-, or hydrophobic interactions or appreciable binding to relevant human antigens. MS-Hu6 showed the same level of "humanness" as human IgG1 in silico, and was non-immunogenic in ELISPOT assays for IL-2 and IFN{gamma} in human peripheral blood mononuclear cell cultures. We conclude that MS-Hu6 is efficacious, durable and manufacturable, and is therefore poised for future human testing as a multipurpose therapeutic.

pharmacology and toxicology↗

bioRxiv2022

Subcortical and cortical tracking of communication sound envelopes in challenging listening conditions

Humans and animals constantly face challenging acoustic environments such as various background noises restricting the detection, discrimination and identification of behaviorally salient sounds. Here, we disentangled the role of temporal envelope tracking on the decrease in neuronal and behavioral discrimination between communication sounds in situations of acoustic degradations. We simulated responses of auditory nerve fibers and recorded neuronal activity in cochlear nucleus, inferior colliculus, thalamus and auditory cortex in anesthetized guinea-pigs. Furthermore, a Go/No-Go sound discrimination task involving two of the guinea-pig whistles was performed on mice in silence and noise. For all conditions, we found that auditory neurons better track the slow amplitude modulations (<20 Hz) of the stimulus envelopes than the faster ones. In addition, the decrease in neuronal and behavioral discrimination performance in noise can be explained by an increased similarity of the vocalization envelopes in the low frequency range (<20 Hz). Together, these results suggest that slow envelope tracking is a general property of auditory neurons, and any difference between the slow envelopes of natural stimuli allows coping with degraded conditions.

neuroscience↗

bioRxiv2021

Maf1, a repressor of RNA polymerase III-dependent transcription, regulates bone mass

Maf1, a key repressor of RNA polymerase III-mediated transcription, has been shown to promote mesoderm formation in vitro. Here, we show, for the first time, that Maf1 plays a critical role in the regulation of osteoblast differentiation and bone mass. A high bone mass phenotype was noted in mice with global deletion of Maf1 (Maf1-/- mice), as well as paradoxically, in mice that overexpressed MAF1 in cells of the osteoblast lineage (Prx1-Cre;LSL-Maf1 mice). Osteoblasts isolated from Maf1-/- mice showed reduced osteoblastogenesis ex vivo. Prx1-Cre;LSL-MAF1 mice showed enhanced osteoblastogenesis concordant with their high bone mass phenotype. Thus, the high bone mass phenotype in Maf1-/- mice is likely due to the confounding effects of the global absence of Maf1 in Maf1-/- mice. Expectedly, MAF1 overexpression promoted osteoblast differentiation and shRNA-mediated Maf1 downregulation inhibited differentiation of ST2 cells, overall indicating Maf1 enhances osteoblast formation. We also found that, in contrast to MAF1 overexpression, other perturbations that repress RNA pol III transcription, including Brf1 knockdown and the chemical inhibition of RNA pol III by ML-60218, inhibited osteoblast differentiation. All perturbations that decrease RNA pol III transcription, however, enhanced adipogenesis in ST2 cell cultures. RNA-seq was used to determine the basis for these opposing actions on osteoblast differentiation. The modalities used to alter RNA pol III transcription resulted in distinct changes gene expression, indicating that this transcription process is highly sensitive to perturbations and triggers diverse gene expression programs and phenotypic outcomes. Specifically, Maf1 induced genes in ST2 cells known to promote osteoblast differentiation. Furthermore, genes that are induced during osteoblast differentiation displayed codon bias. Together, these results reveal a novel role for Maf1 and RNA pol III-mediated transcription in osteoblast fate determination and differentiation and bone mass regulation.

cell biology↗

bioRxiv2021

The Hepcidin Regulator Erythroferrone is a New Member of the Erythropoiesis-Iron-Bone Circuitry

Erythroblast erythroferrone (ERFE) secretion inhibits hepcidin expression by sequestering several bone morphogenetic protein (BMP) family members to increase iron availability for erythropoiesis. We report that ERFE expression in osteoblasts is higher compared with erythroblasts, is independent of erythropoietin, and functional in suppressing hepatocyte hepcidin expression. Erfe-/- mice display low-bone-mass arising from increased bone resorption despite a concomitant increase in bone formation. Consistently, Erfe-/- osteoblasts exhibit enhanced mineralization, Sost and Rankl expression, and BMP-mediated signaling ex vivo. The ERFE effect on osteoclasts is mediated through increased osteoblastic RANKL and sclerostin expression, increasing osteoclastogenesis in Erfe-/- mice. Importantly, Erfe loss in {beta}-thalassemic (Hbbth3/+) mice, a disease model with increased ERFE expression, triggers profound osteoclastic bone resorption and bone loss. Together, ERFE exerts an osteoprotective effect by modulating BMP signaling in osteoblasts, decreasing RANKL production to limit osteoclastogenesis, and prevents excessive bone loss during expanded erythropoiesis in {beta}-thalassemia.

physiology↗

bioRxiv2020

Focal Electrical Stimulation of Human Retinal Ganglion Cells

Vision restoration with retinal implants that electrically stimulate retinal ganglion cells (RGCs), which transmit visual information to the brain, is limited by indiscriminate activation of many cells and cell types. Recent work in isolated macaque retina has demonstrated that direct electrical stimulation of RGCs can be performed with single-cell, single-spike resolution. However, the fidelity of epiretinal stimulation has not been examined in the human retina. Here, electrical activation of the major RGC types was examined using large-scale, multi-electrode recording and stimulation in the human retina ex vivo and compared directly to results from macaque. Targeted activation with single-cell, single-spike resolution was often possible without activating overlying axon bundles, at low stimulation current levels similar to those in macaque. Distinct cell types could be identified and targeted based on their distinct electrical signatures. Simulation based on these measurements revealed that a novel, dynamic stimulation approach would produce a nearly optimal evoked visual signal. These results indicate that high-fidelity control of spiking in human RGCs is achievable with extracellular stimulation and that the macaque retina is an accurate model for vision restoration with epiretinal implants.

neuroscience↗

bioRxiv2019

Quantitative Visualization of Hypoxia and Proliferation Gradients Within Histological Tissue Sections

The formation of hypoxic microenvironments within solid tumors is known to contribute to radiation resistance, chemotherapy resistance, immune suppression, increased metastasis, and an overall poor prognosis. It is therefore crucial to understand the spatial and molecular mechanisms that contribute to tumor hypoxia formation to improve the efficacy of radiation treatment, develop hypoxia-directed therapies, and increase patient survival. The objective of this study is to present a number of complementary novel methods for quantifying tumor hypoxia and proliferation, especially in relation to the location of perfused blood vessels.\n\nMultiplexed immunofluorescence staining can produce whole slide scanned image datasets that are amenable for computational pathology analysis. A standard marker analysis strategy is to take a positive pixel count approach, in which a threshold for positive stain is used to compute a positive area fraction for hypoxia. This work is a reassessment of that approach, utilizing not only cell segmentation but also distance to nearest blood vessel in order to incorporate spatial information into the analysis. We describe a reproducible pipeline for the visualization and quantitative analysis of hypoxia using a vessel distance analysis approach. This methodological pipeline can serve to further elucidate the relationship between vessel distance and microenvironment-linked markers such as hypoxia and proliferation, can help to quantify parameters relating to oxygen consumption and hypoxic tolerance in tissues, as well as potentially serve as a hypothesis generating tool for future studies testing hypoxia-linked markers.

bioinformatics↗