Biology subjects

George, M.

Publications and source records attributed to George, M..

12 recordsLinked to original sources

bioRxiv2026

Intermittent parathyroid hormone employs autonomous and non-autonomous mechanisms to drive osteogenesis from Ebf3-expressing skeletal progenitor cells

How systemic hormonal signals coordinate stem cell fate decisions in adult tissues remains incompletely understood. In bone marrow, Cxcl12-abundant reticular (CAR) cells, marked by Early B-cell Factor 3 (Ebf3) expression, are multipotent mesenchymal progenitors that maintain the hematopoietic stem cell niche and serves as a major osteoblast progenitor source during adult bone remodeling. Using inducible lineage tracing coupled with single-cell transcriptomics and conditional genetics in mice, we show that intermittent parathyroid hormone (iPTH; teriparatide) drives osteogenesis from CAR cells by simultaneously engaging cell-intrinsic and cell-extrinsic mechanisms. Directly, iPTH suppresses lineage-enforcing transcription factors Ebf3, Ebf1, and Foxc1, thereby destabilizing progenitor identity and priming CAR cells for osteogenic commitment. Simultaneously, iPTH stimulates osteoclastic bone resorption, releasing TGF{beta} which recruits these primed progenitors to bone surfaces, a process abolished by osteoclast depletion. Preventing CAR cell maturation via Sp7 deletion abrogates iPTH-induced bone gain, establishing these progenitors as essential mediators of bone anabolism. This coupled mechanism, in which intrinsic transcriptional priming converges with extrinsic niche remodeling, is conserved in human CAR cells from teriparatide-treated postmenopausal women, which show concordant suppression of EBF3 and FOXC1 and elevated TGF{beta}-responsive gene signatures. These findings reveal a general principle by which a systemic hormone orchestrates tissue remodeling through simultaneous reprogramming of progenitor identity and remodeling of the niche microenvironment.

physiology↗

bioRxiv2026

Fear Learning Induced Brain Dynamics Predict Individual Extinction Memory Expression following Transcranial Magnetic Stimulation

Fear learning and extinction unfold as time-dependent processes. Herein, we examined how fear learning dynamically reorganizes brain activity immediately after learning, and whether such reorganization can be modulated with TMS application during extinction learning to prospectively predict extinction-memory expression. Eighty-seven healthy adults completed a three-day Pavlovian threat-learning protocol with resting-state fMRI acquired before and after conditioning (Day 1), dorsolateral prefrontal cortex (DLPFC) transcranial magnetic stimulation (TMS) applied during extinction learning (Day 2), and fMRI during extinction recall and renewal (Day 3). Using coactivation pattern analysis with a hidden Markov model within a 24-nodes threat-circuit parcellation, we identified a fear-learning-induced brain state characterized by global threat-circuit coactivation with heightened engagement and transition uncertainty post conditioning, and a progressive increase in engagement across post-conditioning. Critically, conditioning-induced functional connectivity reorganization within this state predicted individual differences in extinction recall- and renewal-related brain activation under TMS-modulated extinction (cross-validated; recall r = 0.47, p = 0.001; renewal r = 0.37, p = 0.01; permutation-tested), but not under natural extinction. Similar associations were observed between neural features and behavioral expression. These findings demonstrate that fear learning reshapes spontaneous brain-state dynamics and that such learning-induced reorganization serves as an interpretable biomarker for neuromodulation-linked extinction-memory expression.

neuroscience↗

bioRxiv2025

Genome-wide CRISPR interference screen identifies Clip2 as a novel regulator of osteocyte maturation and morphology

Osteocytes play critical roles in bone, making them attractive targets for therapeutics to improve bone mass and strength. The genes driving osteocyte maturation and function are not fully understood. Here we aimed to identify novel genes responsible for osteocyte differentiation and dendrite development by performing a genome-wide CRISPR-interference (CRISPRi) screen in the Ocy454 osteocyte-like cell line. We identify CD61 (integrin {beta}3) as a marker of osteocyte maturation: surface CD61 expression increases during osteocyte maturation, and CD61high cells express higher levels of osteocyte marker genes. We then developed a flow cytometry-based assay to quantify surface CD61 protein levels as a phenotypic endpoint for functional genomic screening. In a genome-wide screen, we identified Clip2, which encodes a microtubule binding protein, as one of dozens of genes necessary for CD61 expression. Clip2 inhibition decreased surface CD61 expression, reduced expression of osteocyte-specific genes Dmp1 and Sost, and impaired dendrite morphology in vitro. Together, these results highlight the utility of surface CD61 as a marker of osteocyte maturity and identify a role of the microtubule cytoskeleton for osteocyte differentiation, form, and function.

cell biology↗

bioRxiv2025

A ubiquitous Streptomyces biosynthetic megacluster encodes an arsenal of synergistic biotin-targeting antibiotics

The rise of multidrug-resistant pathogens underscores the urgent need for antibiotics that act through new targets and mechanisms. Biotin metabolism, essential in most bacteria, remains underexploited therapeutically. Here, we uncover a highly conserved, co-located biosynthetic megacluster in Streptomyces, a striking "cluster of clusters", that encodes four distinct natural product families: acidomycin, stravidins, dapamycins, and -methyl-KAPA, and is flanked by genes that encode streptavidin, a high-affinity biotin-binding protein. Remarkably, all molecules target different steps in bacterial biotin metabolism, revealing a multi-pronged natural strategy for biotin starvation. This arrangement of four functionally convergent biosynthetic gene clusters at a single genomic locus is without precedent. Even more surprisingly, we find that this anti-biotin megacluster is widespread across Streptomyces bacteria, suggesting a deeply conserved evolutionary solution to microbial competition. Mechanistically, the compounds inhibit biotin biosynthesis through enzyme blockade, prodrug activation, covalent cofactor mimicry, and biotin sequestration via co-expressed streptavidin. Stravidin S2 and -methyl-KAPA are effective in a murine model of multidrug-resistant E. coli infection. These findings expose a coordinated biosynthetic logic in microbial secondary metabolites and point to higher-order biosynthetic architectures as promising reservoirs of antibiotic innovation.

microbiology↗

bioRxiv2025

BC-Predict Database: A Curated Resource of Experimentally Validated Markers in Multidrug Resistance in Breast Cancer

BackgroundIn this study, we aim to develop a yearly updatable database that could predict chemotherapeutic drug resistance and overall survival probability in breast cancer patients. Existing drug sensitivity databases depend on correlation-based predictions. In our study, candidates involved in drug resistance are chosen based on cell line validation (overexpression or downregulation or inhibition of candidates) studies, curated manually. Method28,773 mRNA expression signatures from 914 breast cancer patients were extracted from cProsite. 106 of these patients had clinical information and log2 fold change information required for this study. We categorized these patients into deceased and surviving groups from TCGA. To prepare a database that can predict drug resistance and overall survival, we included mRNAs that were over-expressed in at least 80% of the breast cancer patients and mRNAs over-expressed in deceased and surviving groups. In addition, we also reported breast cancer-associated drug resistance candidates which have been reported in cell-line based studies. The database matrix preparation involved an approximate of 15000 manual searches of cell validated studies. (750 candidates x 20 drugs). The database was validated using a publicly available breast cancer patient proteomics data. ResultsOur analysis identified a list of top priority candidates associated with multidrug resistance, categorized based on their resistance to >15 drugs, 5-15 drugs, and 2-4 drugs. Analysis of patient profiles in the database revealed that the number of proteins contributing to drug resistance was high in the poor prognosis category compared to the good prognosis category. ConclusionsOur study highlights the probable gaps in breast cancer drug resistance research, as only a small subset of overexpressed mRNA candidates found in patients are studied in vitro or in vivo experiments focusing on drug resistance. We also identified candidates involved in multidrug resistance, whose role in drug resistance has not been studied in more than 15 drugs. After further validations, this will benefit the clinicians and upcoming CRISPR gene therapeutics.

cancer biology↗

bioRxiv2025

Longitudinal transcriptomic analysis of SIV-infected rhesus macaques reveals peripheral immune dynamics throughout untreated SIV infection and long-term antiretroviral therapy

Developing a working knowledge of immune dynamics during prolonged infection and treatment has become critical for both advancing HIV cure strategies and understanding non-AIDS comorbidities, given rises in the age and average time spent on antiretroviral therapy (ART) among people living with HIV. However, at present, we do not fully appreciate the ways in which prolonged suppressive therapy influences immune function. Toward addressing this key knowledge gap comprehensively, we applied single-cell RNA-sequencing (scRNA-seq) to longitudinally profile peripheral blood mononuclear cells from SIV-infected non-human primates longitudinally. Our data reveal significant immune shifts during acute and chronic infection, as well as over five years of subsequent ART. We observe a decline in CD4+ T cells and an increase in aberrant B cells and CD16+ monocytes during untreated chronic infection, as well as widespread dampened transcriptional activity. Further, we uncover transcriptional signatures suggestive of unresolved immune dysregulation during long-term suppressive therapy - most prominently among myeloid cell populations. By examining concurrent measurements of intact proviral DNA, we link peripheral responses to reservoir size via IPDA. We furthermore identify ribosomal-associated pathways as key differentiators of infection stage, treatment status, and time on ART. Finally, we tested whether previously published transcriptional correlates of differential outcomes (e.g. viral rebound, vaccine efficacy) changed over time on ART. Overall, our findings capture dynamic immune remodeling from acute infection through long-term ART, highlighting complexities in achieving complete immune recovery that may influence future therapeutic strategies.

immunology↗

bioRxiv2024

Impact of variants and vaccination on nasal immunity across three waves of SARS-CoV-2

SARS-CoV-2 infection and COVID-19 disease vary with respect to viral variant and host vaccination status. However, how vaccines, emergent variants, and their intersection shift host responses in the human nasal mucosa remains uncharacterized. We and others have shown during the first SARS-CoV-2 wave that a muted nasal epithelial interferon response at the site of infection underlies severe COVID-19. We sought to further understand how upper airway cell subsets and states associate with COVID-19 phenotypes across viral variants and vaccination. Here, we integrated new single-cell RNA-sequencing (scRNA-seq) data from nasopharyngeal swabs collected from 67 adult participants during the Delta and Omicron waves with data from 45 participants collected during the original (Ancestral) wave in our prior study. By characterizing detailed cellular states during infection, we identified changes in epithelial and immune cells that are both unique and shared across variants and vaccination status. By defining SARS-CoV-2 RNA+ cells for each variant, we found that Delta samples had a marked increase in the abundance of viral RNA+ cells. Despite this dramatic increase in viral RNA+ cells in Delta cases, the nasal cellular compositions of Delta and Omicron exhibit greater similarity, driven partly by myeloid subsets, than the Ancestral landscapes associated with specialized epithelial subsets. We found that vaccination prior to infection was surprisingly associated with nasal macrophage recruitment and activation rather than adaptive immune cell signatures. While patients with severe disease caused by Ancestral or Delta variants had muted interferon responses, Omicron-infected patients had equivalent interferon responses regardless of disease severity. Our study defines the evolution of cellular targets and signatures of disease severity in the upper respiratory tract across SARS-CoV-2 variants, and suggests that intramuscular vaccines shape myeloid responses in the nasal mucosa upon SARS-CoV-2 infection.

immunology↗

bioRxiv2021

Role of RALBP1 in Oxidative Stress and Mitochondrial Dysfunction in Alzheimer's Disease

The purpose of our study is to understand the role of the Ralbp1 gene in oxidative stress (OS), mitochondrial dysfunction and cognition in Alzheimers disease (AD) pathogenesis. The Ralbp1 gene encodes the 76 kDa protein Rlip (aka RLIP76). Previous studies have revealed its role in OS-related cancer. However, Rlip is transcriptionally regulated by EP300, a CREB-binding protein that is important for synaptic plasticity in the brain. Rlip functions as a stress-responsive/protective transporter of glutathione conjugates (GS-E) and xenobiotic toxins. OS causes rapid cellular accumulation of Rlip and its translocation from a tubulin-bound complex to the plasma membrane, mitochondria and nucleus. Therefore, Rlip may play an important role in maintaining cognitive function in the face of OS-related injury. This study is aimed to determine whether Rlip deficiency in mice is associated with AD-like cognitive and mitochondrial dysfunction. Brain tissue obtained from cohorts of wildtype and Rlip+/- mice were analyzed for OS markers, expression of genes that regulate mitochondrial fission/fusion, and synaptic integrity. We also examined mitochondrial ultrastructure in mouse brains obtained from these mice and further analyzed the impact of Rlip deficiency on gene networks of AD, aging, inhibition of stress-activated gene expression, mitochondrial function, and CREB signaling. Our studies revealed a significant increase in the levels of OS markers and alterations in the expression of genes and proteins involved in mitochondrial biogenesis, dynamics and synapses in brain tissues of these mice. Furthermore, we compared the cognitive function of wildtype and Rlip+/- mice. Behavioral, basic motor and sensory function tests in Rlip+/- mice revealed cognitive decline, similar to AD. Gene network analysis indicated dysregulation of stress-activated gene expression, mitochondrial function, and CREB signaling genes in the Rlip+/- mouse liver. Our results suggest that the Rlip deficiency-associated increase in OS and mitochondrial dysfunction could contribute to the development of OS-related AD processes. Therefore, the restoration of Rlip activity and endogenous cytoprotective mechanisms by pharmacological interventions is a novel approach to protect against AD.

neuroscience↗

bioRxiv2021

Impaired local intrinsic immunity to SARS-CoV-2 infection in severe COVID-19

Infection with SARS-CoV-2, the virus that causes COVID-19, can lead to severe lower respiratory illness including pneumonia and acute respiratory distress syndrome, which can result in profound morbidity and mortality. However, many infected individuals are either asymptomatic or have isolated upper respiratory symptoms, which suggests that the upper airways represent the initial site of viral infection, and that some individuals are able to largely constrain viral pathology to the nasal and oropharyngeal tissues. Which cell types in the human nasopharynx are the primary targets of SARS-CoV-2 infection, and how infection influences the cellular organization of the respiratory epithelium remains incompletely understood. Here, we present nasopharyngeal samples from a cohort of 35 individuals with COVID-19, representing a wide spectrum of disease states from ambulatory to critically ill, as well as 23 healthy and intubated patients without COVID-19. Using standard nasopharyngeal swabs, we collected viable cells and performed single-cell RNA-sequencing (scRNA-seq), simultaneously profiling both host and viral RNA. We find that following infection with SARS-CoV-2, the upper respiratory epithelium undergoes massive reorganization: secretory cells diversify and expand, and mature epithelial cells are preferentially lost. Further, we observe evidence for deuterosomal cell and immature ciliated cell expansion, potentially representing active repopulation of lost ciliated cells through coupled secretory cell differentiation. Epithelial cells from participants with mild/moderate COVID-19 show extensive induction of genes associated with anti-viral and type I interferon responses. In contrast, cells from participants with severe lower respiratory symptoms appear globally muted in their anti-viral capacity, despite substantially higher local inflammatory myeloid populations and equivalent nasal viral loads. This suggests an essential role for intrinsic, local epithelial immunity in curbing and constraining viral-induced pathology. Using a custom computational pipeline, we characterized cell-associated SARS-CoV-2 RNA and identified rare cells with RNA intermediates strongly suggestive of active replication. Both within and across individuals, we find remarkable diversity and heterogeneity among SARS-CoV-2 RNA+ host cells, including developing/immature and interferon-responsive ciliated cells, KRT13+ "hillock"-like cells, and unique subsets of secretory, goblet, and squamous cells. Finally, SARS-CoV-2 RNA+ cells, as compared to uninfected bystanders, are enriched for genes involved in susceptibility (e.g., CTSL, TMPRSS2) or response (e.g., MX1, IFITM3, EIF2AK2) to infection. Together, this work defines both protective and detrimental host responses to SARS-CoV-2, determines the direct viral targets of infection, and suggests that failed anti-viral epithelial immunity in the nasal mucosa may underlie the progression to severe COVID-19.

immunology↗

bioRxiv2021

Differential serotonin uptake mechanisms at the human maternal-fetal interface

Mechanisms regulating serotonin (5-HT) homeostasis at the maternal-fetal interface are important for proper placental functioning and fetal (neuro)development. Here we studied 5-HT uptake mechanisms in human primary trophoblasts, feto-placental endothelial cells and cord blood platelets, all isolated directly after birth. Trophoblasts and cord blood platelets demonstrated high-affinity 5-HT uptake with similar Michaelis constant (Km) values (0.60{+/-}0.27 and 0.65{+/-}0.18 M, respectively). In contrast, feto-placental endothelial cells displayed saturation kinetics only over the low-affinity range of 5-HT concentrations (Km=782{+/-}218 M). 5-HT uptake into trophoblasts was inhibited by various psychotropic drugs targeting high-affinity serotonin transporter (SERT), and into feto-placental endothelial cells by an inhibitor of low-affinity transporters. SERT mRNAs were abundant in trophoblasts, but sparse in feto-placental endothelial cells; the opposite was found for transcripts of the low-affinity plasma membrane monoamine transporter (PMAT). These results show for the first time the presence of functional 5-HT uptake systems in feto-placental endothelial cells and fetal platelets, cells in direct contact with the fetal blood plasma. Data also emphasize sensitivity of 5-HT transport into trophoblasts, cells facing maternal blood, to various psychotropic drugs. The multiple, high- and low-affinity, systems present for cellular 5-HT uptake highlight the importance of maintaining 5-HT homeostasis at the maternal-fetal interface.

cell biology↗

bioRxiv2019

Minimal in vivo requirements for developmentally regulated cardiac long intergenic non-coding RNAs

Long intergenic non-coding RNAs (lincRNAs) have been implicated in aspects of gene regulation, but their requirement for development needs empirical interrogation. To begin to understand the roles lincRNAs might play in heart development, we computationally identified nine murine lincRNAs that have developmentally regulated transcriptional and epigenomic profiles specific to early heart differentiation. Six of the nine lincRNAs had in vivo expression patterns supporting a potential function in heart development, including a transcript downstream of the cardiac transcription factor Hand2 that we named Handlr (Hand2-associated lincRNA), Rubie, and Atcayos. We genetically ablated these six lincRNAs in mouse, which implicated genomic regulatory roles to four of the cohort, However, none of the lincRNA deletions led to severe cardiac phenotypes. Thus, we stressed the hearts of adult Handlr and Atcayos mutant mice by transverse aortic banding and found that absence of these lincRNAs did not affect cardiac hypertrophy or left ventricular function post-stress. Our results support roles for lincRNA transcripts and/or transcription to regulation of topologically associated genes. However, the individual importance of developmentally-specific lincRNAs is yet to be established. Their status as either gene-like entities or epigenetic components of the nucleus should be further considered.

developmental biology↗

bioRxiv2018

The allometry of brain size in mammals

Why some animals have big brains and others do not has intrigued scholars for millennia. Yet, the taxonomic scope of brain size research is limited to a few mammal lineages. Here we present a brain size dataset compiled from the literature for 1552 species with representation from 28 extant taxonomic orders. The brain-body size allometry across all mammals is (Brain) = -1.26 (Body)0.75. This relationship shows strong phylogenetic signal as expected due to shared evolutionary histories. Slopes using median species values for each order, family, and genus, to ensure evolutionary independence, approximate [~]0.75 scaling. Why brain size scales to the [3/4] power to body size across mammals is, to our knowledge, unknown. Slopes within taxonomic orders exhibiting smaller size ranges are often shallower than 0.75 and range from 0.24 to 0.81 with a median slope of 0.64. Published brain size data is lacking for the majority of extant mammals (>70% of species) with strong bias in representation from Primates, Carnivores, Perrisodactyla, and Australidelphian marsupials (orders Dasyuromorphia, Diprotodontia, Peramelemorphia). Several orders are particularly underrepresented. For example, brain size data are available for less than 20% of species in each of the following speciose lineages: Soricomorpha, Rodentia, Lagomorpha, Didelphimorphia, and Scandentia. Use of museum collections can decrease the current taxonomic bias in mammal brain size data and tests of hypothesis.

animal behavior and cognition↗