Biology subjects

Bose, M.

Publications and source records attributed to Bose, M..

At least 19 recordsLinked to original sources

bioRxiv2026

DLL3 expression predicts response and long-term outcome in small cell lung cancer patients treated with tarlatamab

Background: Small cell lung cancer (SCLC) is an aggressive, high-grade neuroendocrine carcinoma (hgNEC) with poor prognosis. Tarlatamab, a DLL3-targeting T cell engager was approved in 2024 for relapsed SCLC, with almost doubled overall survival benefit compared to chemotherapy. However, over half of patients do not respond to tarlatamab and others develop resistance within months. With multiple DLL3-targeting therapies in clinical trials, there are currently no validated predictive biomarkers to identify patients most likely to benefit from tarlatamab. In this study, we evaluate baseline DLL3 IHC level in patients as a predictive biomarker to tarlatamab clinical outcome. Methods: We assembled a cohort of 138 patients within IRB-approved MD Anderson GEMINI database (PA13-0589) with DLL3 expression by CLIA-validated immunohistochemistry (IHC), and those treated with tarlatamab from 7/1/2024 to 3/30/2026. Only those with DLL3 IHC results and treated with tarlatamab were included in this predictive biomarker study. All DLL3 levels were reported as percentage cells with cytoplasmic or surface DLL3 expression, including 24 with additional intensity score and H-score calculation. demographic, clinical, and outcome data were collected. Systemic and intracranial response data were assessed by RECIST and mRANO BM criteria respectively. Longitudinal liquid biopsies were taken from a subset of patients for circulating tumor DNA (ctDNA) and (Cytometry by Time-of-Flight) CyTOF analyses. Results: In the predictive biomarker cohort of 54 patients with SCLC treated with tarlatamab, Median DLL3% level in tarlatamab treated cohort was 75%. Median follow-up time was 9.9 months, median time on tarlatamab treatment (ToT) was 5.8 months. At the data cut-off, 61% (33 out of 54) patients were alive. Kaplan-Meier curve stratified by DLL3 % of <=75% vs. >75 showed significant longer ToT and a trend toward longer median OS (mOS). In DLL3>75% compared to DLL3 <=75%: mToT was 10.1 months vs. 2.9 months (p=0.036), mOS: not reached vs. 9.5 months (p= 0.066). Among 41 patients who completed one cycle of tarlatamab treatment and were eligible for systemic (extra-cranial) response per RECIST criteria; we observed partial response (PR) in 51% (21) patients, stable disease (SD) in 22% (9) patients; and progressive disease (PD) in 27% (11) patients. The median DLL3 % in those with PR vs. PD were 80% vs. 40% (p=0.006); median DLL3% comparing PR and SD were 80% vs. 60% (p=0.051). Among 35 patients evaluable for intracranial response, best objective response prior to any brain radiation were 5 (14%) CR,11(31%) PR, 8 (23%) SD and 11 (31%) PD. 9 received brain radiation (8 SRS, 1 WBRT) during tarlatamab to achieve better intracranial control while systemic control is maintained. DLL3% does not appear to be correlated with intracranial response. Longitudinal ctDNA and CyTOF analyses showed persistent ctDNA positivity, as well as increasing NEUROD1 subtype cells in circulating tumor cells in post-tarlatamab progression samples. We additionally profiled DLL3 expression by IHC in 138 patients with SCLC and found heterogenous DLL3 expression, with Median DLL3% of 70% across different biopsy sites. Conclusions: Our data suggests DLL3 expression in patients with SCLC is heterogeneous and not ubiquitous, with median DLL3 IHC of 70%. DLL3 IHC predicts objective response and long-term outcome with tarlatamab. In addition, dynamic monitoring of ctDNA level and CTCs by CyTOF are suggestive of development of tarlatamab resistance, however further studies with larger cohort of paired longitudinal samples are needed to validate the novel blood-based biomarkers. To our knowledge, this study is the first to validate DLL3 IHC as a predictive biomarker for tarlatamab in SCLC, which leads the way for optimizing treatment selection and combinatorial therapies for the subset of patients less likely to respond to tarlatamab.

cancer biology↗

bioRxiv2026

Loss of a conserved disulfide bond defines Penetration2-related immune myrosinases in Brassicaceae

O_LIThis study investigated whether PEN2/BGLU26 has uniquely evolved as an indole glucosinolate-hydrolysing myrosinase required for Arabidopsis thaliana pre-invasive immunity, or whether related myrosinases can replace its function when targeted to the same subcellular context. C_LIO_LIPEN2-homologous and other selected myrosinases from A. thaliana and Brassica rapa were expressed in the pen2-2 mutant background using a PEN2-like targeting strategy. The resulting lines were assessed by gene expression, protein accumulation, metabolite analysis and pathogen resistance assays. In parallel, targeted mutagenesis, structural comparison and phylogenetic analysis were used to examine molecular and evolutionary features of PEN2-related myrosinases. C_LIO_LIAtBGLU27 and BrBABG.a, but not AtBGLU18, AtBGLU23 or AtBGLU28, partially restored indole glucosinolate hydrolysis and resistance to Colletotrichum tropicale in pen2-2. Unlike AtPEN2, both enzymes acted mainly constitutively and showed distinct substrate preferences. PEN2, BGLU27 and BABG proteins lacked conserved post-translational modification sites, including residues associated with a conserved disulfide bond. Restoring this disulfide bond in AtPEN2 abolished its activity. C_LIO_LIPEN2-related myrosinases form an evolutionarily distinct BGLU lineage associated with indole glucosinolate metabolism in Brassicales. Loss of the conserved disulfide bond appears to be required for PEN2 activity, whereas additional PEN2-specific regulatory features are needed for pathogen-triggered, rather than constitutive, glucosinolate metabolism. C_LI

plant biology↗

bioRxiv2026

Salmonberry Transcriptome Reveals Phylogeny and Novel Badnavirus Species

The Rosaceae family comprises thousands of species across over 100 genera, including Salmonberry (Rubus spectabilis), a Pacific Northwest native within the diverse Rubus genus. Its berries and leaves are used for food and medicinal purposes, and ecologically it functions as a pioneer species that supports biodiversity and limits erosion. Although many Rubus genomes were sequenced and analyzed, salmonberry remains undercharacterized: despite a recently sequenced genome, no publicly available annotation or gene expression analysis currently exists. Here, we used RNA sequencing to characterize the salmonberry leaf transcriptome and examine its phylogenetic relationship within Rubus. The assembled 63,285 unique transcripts included 1,389 high-confidence lncRNA transcripts expressed in salmonberry leaves, 218 of which are conserved across Rubus. Phylogenetic analysis indicates that salmonberry is closely related to Rubus arcticus. In addition, we detected a novel species of virus associated with salmonberry. These findings provide foundational genomic resources for R. spectabilis and offer new insights into its evolutionary relationships and endogenous viral integrations.

plant biology↗

bioRxiv2026

Nanoscale visualization of ribonucleoprotein condensates with ultrastructure RNA expansion microscopy

Superresolution imaging of RNAs in their native cellular context is crucial for investigating RNA biology. Here, we develop Ultrastructure RNA Expansion (UREx) microscopy, an expansion microscopy approach, that retains cellular RNAs and RNP granule condensates. We demonstrate that UREx retains the highly ordered core-shell architecture of Neat1 RNA in the paraspeckles, confirming RNA ultrastructure preservation. In addition to robust RNA retention, UREx also preserves protein epitopes and overall cellular protein ultrastructure thus enabling context-dependent visualization of RNAs in cells as well as intact tissues. Employing UREx, we visualize RNP condensates in the intact Drosophila germline and resolve diffraction-limited oskar granules into RNP nanoclusters. Together, our findings establish UREx as a broadly applicable and cost-effective resource to interrogate the nanoscale spatial organization of RNAs and proteins within diffraction-limited RNP assemblies.

cell biology↗

bioRxiv2026

Complement 3a Receptor mediates high fat diet induced hypothalamic accumulation of lipid associated microglia to regulate neuroinflammation and obesity

Microglia, the resident macrophages of the central nervous system, are recognized for their heterogeneity and integral role in brain function and diseases. In the context of high fat diet (HFD) feeding and obesity, microglia become overactive, acquiring a prevailing lipid associated microglial phenotype (also known as LAM). Yet, how microgliosis is induced and regulated remains unclear. Here we report a key role for the Complement 3a Receptor (C3aR), on HFD-induced hypothalamic gliosis and weight gain in mice. HFD consumption leads to elevated microglial expression of C3aR, which parallels widespread accumulation of reactive microglia, selectively in the hypothalamus. Conditional microglial C3aR deletion protects mice from HFD-induced hypothalamic reactive microgliosis. C3aR deletion or pharmacological antagonism opposes HFD-induced weight gain in male but not female mice. Mechanistically, we demonstrated that C3aR is essential for lipid-induced lipid droplet formation, and acquisition of a LAM molecular signature. In summary, we uncovered a previously unknown role for C3aR in the acquisition of a LAM signature driving diet-induced gliosis, identifying this receptor as a new viable therapeutic candidate for conditions associated with hypothalamic neuroinflammation.

immunology↗

bioRxiv2025

CyTOF-based profiling of circulating tumor cells predicts aggressiveness and therapy response in SCLC liquid biopsies at a personalized level

Small-cell lung cancer (SCLC) is an aggressive neuroendocrine carcinoma characterized by high numbers of circulating tumor cells (CTCs). We applied CyTOF and a 20-marker antibody panel to detect and phenotype CTCs directly in liquid biopsies of 51 SCLC patients (treatment-naive, chemotherapy and immunotherapy-treated, and tarlatamab-treated), of which a subset were longitudinally tracked. Unsupervised clustering revealed distinct cell populations enriched in patient liquid biopsies compared to those from healthy donors. Further analysis identified CTC populations of the three established SCLC subtypes driven by the high expression of ASCL1, NeuroD1, and POU2F3 transcription factors respectively. Significant differences in CTC EMT markers, established therapeutic targets (e.g. DLL3), and subtype heterogeneity were observed between naive versus treated samples. Changes in subtype proportions were observed in longitudinally tracked samples in both treatment modalities. Our study demonstrates the utility of CyTOF for high-resolution CTC profiling, offering dynamic insights into CTC heterogeneity, treatment response, and resistance mechanisms. HighlightsO_LICTCs can be detected, subtyped and phenotyped in SCLC liquid biopsies using CyTOF C_LIO_LICTC subtypes and EMT states are differentially associated with treatment modality C_LIO_LICTC DLL3 levels and epithelial features increase following anti-DLL3 BiTE therapy C_LIO_LICyTOF CTC subtyping can predict disease aggressiveness C_LIO_LILongitudinal tracking reveals CTC plasticity and therapy response correlations C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=132 SRC="FIGDIR/small/694669v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@384cbcorg.highwire.dtl.DTLVardef@35dd37org.highwire.dtl.DTLVardef@4e7d61org.highwire.dtl.DTLVardef@1098e4f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

YAP1 defines an emergent, plastic population of relapsed small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive neuroendocrine malignancy characterized by rapid onset of chemoresistance and poor clinical outcomes. Transcriptional heterogeneity among treatment-naive SCLC tumors underlies four transcriptional subtypes, each with distinct clinical vulnerabilities. Though previously hypothesized to delineate a distinct subtype, expression of YAP1 is largely absent from treatment-naive, pure SCLC. To characterize relapsed SCLC, circulating tumor DNA, circulating tumor cells, and core needle biopsies from SCLC patients and preclinical models following resistance to standard-of-care therapies were analyzed. In contrast to treatment-naive SCLC, these analyses reveal an emergent YAP1-positive cell population that coincides with treatment resistance. These YAP1-positive cells exhibit characteristics of drug tolerant persister cells, including senescence, stemness, and plasticity, as YAP1 positive cells largely abandon features characteristic of SCLC to adopt those of large-cell neuroendocrine carcinoma (LCNEC). As a result of this SCLC-like to LCNEC-like evolution, YAP1-positive cells lack several clinically relevant SCLC surface targets (i.e., DLL3, SEZ6), but are enriched for others (i.e., B7-H3, TROP2). We propose a model where YAP1 expressing cells emerge with SCLC treatment resistance and characterize a tenacious subpopulation capable of diverging from the treatment naive lineage and adopting features to evade therapeutic response.

cancer biology↗

bioRxiv2025

Integrative Microbiome Profiling of Colorectal Cancer Across South Asian and Western Cohorts Using Interpretable Machine Learning

The incidence of colorectal cancer (CRC) cases has been steadily rising in South Asian countries compared to western countries. Microbiome dysbiosis has been strongly associated with CRC development, with diet and demographic factors playing an important role in shaping gut microbial composition. Since most CRC cases are diagnosed at advanced stages, early detection remains critical for improving patient outcomes. Machine learning (ML) approaches provide a promising strategy to identify predictive microbial biomarkers for early CRC detection. In this study, we have analyzed publicly available 16S rRNA datasets comprising CRC patients and controls from South Asian cohorts (India and Sri Lanka) and compared them with Western cohorts (USA). Our findings revealed a higher relative abundance of Prevotella in South Asian cohorts, whereas Bacteroides predominated in the USA cohort. Across all three datasets, Fusobacterium, Escherichia-Shigella, and Akkermansia were consistently elevated in CRC cases. We evaluated multiple ML algorithms, including Decision Tree, Random Forest, AdaBoost, LogitBoost, XGBoost, Support Vector Machine (SVM), and k-Nearest Neighbors (KNN) and proposed stacked ensemble model to differentiate between CRC and controls. Stacked ensemble model has higher accuracy compared to base models. To improve models interpretability and transparency SHAP (SHapley Additive exPlanations) analysis were performed to identify key taxa influencing model predictions. These results underscore the utility of ML-based microbiome analysis for identifying robust CRC-associated microbial signatures, with potential application in developing generalizable early detection tools.

microbiology↗

bioRxiv2025

A new typing scheme demonstrates high discriminatory power for Treponema pallidum subspecies

The global resurgence of treponematoses, particularly syphilis, poses a growing public health challenge. Despite recent advances in sequencing technologies, obtaining complete Treponema pallidum genome sequences for epidemiological studies remains time-consuming and challenging due to the difficulty related to procuring clinical samples with sufficient treponemal burden to fulfil the sequencing requirements. There is an urgent need for rapid, cost-effective and accessible typing methods suitable for laboratories with Sanger sequencing resources. Based on the analysis of 121 T. pallidum genomes from geographically diverse regions, we selected seven highly variable genes to form the basis of this new typing system. These seven genes show high discrimination capacity, identifying many allelic profiles among T. pallidum isolates. Importantly, the scheme employs a single-step PCR protocol for the amplification and sequencing of all seven targets enabling straightforward implementation in standard laboratory settings. The MLST was validated using a diverse set of T. pallidum clinical samples from across the globe. A significant proportion of the tested samples showed macrolide resistance, emphasizing the need for epidemiological surveillance. Utilizing this new tool, we have analyzed the genetic variation within and between populations of T. pallidum, considering the geographical origin of the samples. Population structure analysis revealed distinct genetic clusters, underlining complex transmission dynamics of T. pallidum, shaped by local epidemiological factors. The MLST scheme is publicly accessible through the PubMLST database, encouraging widespread adoption in standard laboratories due to this database being user-friendly, intuitive, and fast to implement. The novel MLST scheme offers a promising tool to advance the study of the molecular epidemiology of T. pallidum, facilitate tracking transmission, and establish a global surveillance network with the overall goal of strengthening public health interventions for syphilis control.

microbiology↗

bioRxiv2025

Endothelial-leukocyte interaction in CAR T cell neurotoxicity

CAR-T cells treat cancer, but also cause systemic cytokine release and immune effector cell associated neurotoxicity syndrome (ICANS). In an immunocompetent mouse model, we show by in vivo two-photon imaging that CD19-CAR T treatment causes brain capillary plugging by circulating CAR-T cells and other CD45+ leukocytes, as well as cortical hypoxia. This is accompanied by increased endothelial ICAM-1 and VCAM-1 expression in the brain capillary-venule transition zone, where most of the capillary stalls occur. In the mouse model, circulating CAR-T cells strongly upregulate integrin 4{beta}1 affinity to VCAM-1, but not affinity of integrin L{beta}2 to ICAM-1. Blockade of integrin 4 but not integrin L improves locomotion behavior. In vitro, human brain microendothelial cells upregulate ICAM-1 more than VCAM-1 in response to TNF, IFN-{gamma}, and IL-1{beta}. In a 3D brain human microvessel model, treatment with TNF and IFN-{gamma} is sufficient to induce adhesion of CAR T cells under flow conditions, which is blocked synergistically by antibodies against integrins 4 and L. Finally, patients with the highest levels of TNF and IFN-{gamma} also have the highest blood levels of soluble ICAM-1 and VCAM-1, which in turn correlate with ICANS. Integrin 4 but not L increases in CAR-T cells after they are infused into patients. Combined data from patients, mouse models and in vitro microvessels indicate differential regulation of interactions of ICAM-1 and VCAM-1 with their respective leukocyte integrins. Overall, our study supports the hypothesis that cytokine-driven upregulation of endothelial-leukocyte adhesion is sufficient to induce acute, reversible neurotoxicity. One Sentence SummaryDuring CAR T cell therapy, cytokine release induces white blood cell stalling in brain capillaries by upregulating ICAM-1/VCAM-1-integrin interactions.

immunology↗

bioRxiv2025

Distinct memory CD4 subset tropism of two CCR5-tropic HIV-1 in a rapid progressor

CCR5 tropic HIV-1 mainly infect memory CD4+ T cells. Memory CD4+ T cells are heterogenous which comprise central memory (CM), transitional memory (TM) and effector memory (EM) subsets based on cell differentiation stages. Previous studies demonstrate that low viral burden in the CM subset correlates with long-term non-progressive HIV-1 infection (1, 2) and is a hallmark of non-pathogenetic SIV infection (3, 4). These findings indicate the importance of CD4 subset tropism of HIV/SIV in determining disease progression. However, an important, yet unanswered question is whether CCR5 HIV-1 variants have different memory CD4 subset preferences. Here, we demonstrate clear compartmentalization of two CCR5 HIV-1 in different memory CD4 subsets in vivo.

microbiology↗

bioRxiv2024

Single-cell analyses reveal that monocyte gene expression profiles influence HIV-1 reservoir size in acutely treated cohorts

Elimination of latent HIV-1 is a major goal of AIDS research but the host factors determining the size of these reservoirs are poorly understood. Here, we investigated whether differences in host gene expression modulate the size of the HIV-1 reservoir during suppressive ART. Peripheral blood mononuclear cells (PBMC) from fourteen individuals initiating ART during acute infection who demonstrated effective viral suppression but varying magnitude of total HIV-1 DNA were characterized by single-cell RNA sequencing (scRNA-seq). Differentially expressed genes and enriched pathways demonstrated increased monocyte activity in participants with undetectable HIV-1 reservoirs. IL1B expression in CD14+ monocytes showed the greatest fold difference. The inverse association of IL1B with reservoir size was validated in an independent cohort comprised of 38 participants with different genetic backgrounds and HIV-1 subtype infections, and further confirmed with intact proviral DNA assay (IPDA(R)) measurements of intact HIV-1 proviruses in a subset of the samples. Modeling interactions with cell population frequencies showed that monocyte IL1B expression associated inversely with reservoir size in the context of higher frequencies of central memory CD4+ T cells, implicating an indirect effect of IL1B via the cell type well established to be a reservoir for persistent HIV-1. Signatures consisting of co-expressed genes including IL1B were highly enriched in the "TNF signaling via NF-{kappa}B" geneset. Functional analyses in cell culture revealed that IL1B activates NF-{kappa}B, thereby promoting productive HIV-1 infection while simultaneously suppressing viral spread, suggesting a natural latency reversing activity to deplete the reservoir in ART treated individuals. Altogether, unbiased high throughput scRNA-seq analyses revealed that monocyte IL1B variation could decrease HIV-1 proviral reservoirs in individuals initiating ART during acute infection.

immunology↗

bioRxiv2024

Alterations in genes associated with cytosolic RNA sensing in whole blood are associated with coronary microvascular disease in SLE

ObjectiveTo investigate whether gene signatures discriminate systemic lupus erythematosus (SLE) patients with coronary microvascular dysfunction (CMD) from those without and whether any signaling pathway is linked to the underlying pathobiology of SLE CMD. MethodsThis study collected whole blood RNA samples from female subjects aged 37 to 57, comprising 11 SLE patients (4 SLE-CMD, 7 SLE-non-CMD) and 10 HC. Total RNA was then used for library preparation and sequencing. Differential gene expression analysis was performed to identify gene signatures associated with CMD in SLE patients using DEseq2 v1.42.0. Gene Set Enrichment Analysis were performed by ClusterProfiler v4.10.0 and pathfindR v2.3.1. ResultsRNA-seq analysis revealed 143 differentially expressed (DE) genes between the SLE and HC groups. GO analysis indicated associations with virus defense and interferon signaling in SLE. 14 DE genes were identified from comparison between SLE-CMD and SLE-non-CMD with adjusted parameters (padj < 0.1). Notably, SLE-CMD exhibited elevated levels of genes associated with RNA sensing, while downregulated genes in SLE-non-CMD were associated with blood coagulation and cell-cell junction. Further investigation highlighted differences in IFN signaling and ADP-ribosylation pathways between SLE-CMD and SLE-non-CMD, suggesting distinct molecular mechanisms underlying vascular changes in CMD and reduced left ventricular function in non-CMD. ConclusionOur study identified a unique gene signature in SLE-CMD compared to the HC group, highlighting the significant involvement of type 1 interferon, RIG-I family proteins, and chronic inflammation in the progression of SLE-CMD. The intricate relationship between SLE-CMD and these factors underscores their probable role in initiating and advancing SLE-CMD.

bioinformatics↗

bioRxiv2024

LHX2 regulates dendritic morphogenesis in layer II/III of the neocortex via distinct pathways in progenitors and postmitotic neurons.

In the mammalian neocortex, excitatory neurons that send projections via the corpus callosum are critical to integrating information across the two brain hemispheres. The molecular mechanisms governing the development of the dendritic arbours and spines of these callosal neurons are poorly understood, yet these features are critical to their physiological properties. LIM Homeodomain 2 (Lhx2), a regulator of fundamental processes in cortical development, is expressed in postmitotic callosal neurons occupying layer II/III of the neocortex and also in their progenitors residing in the embryonic day (E) 15.5 ventricular zone of the mouse neocortex. We tested whether this factor is essential for dendritic arbour configuration and spine morphogenesis of layer II/III neurons. Here, we report loss of Lhx2, either in postmitotic layer II/III neurons or their progenitors, resulted in shrunken dendritic arbours and perturbed spine morphology. The defects were more pronounced upon Lhx2 disruption in progenitors, and were recapitulated when this was driven exclusively in basal progenitors. In postmitotic neurons, LHX2 regulates dendritic and spine morphogenesis via the canonical Wnt /{beta} Catenin signalling pathway. Constitutive activation of this pathway in postmitotic neurons mimics the Lhx2 loss-of-function phenotype. In E15.5 progenitors, LHX2 acts in part via bHLH transcription factor NEUROG2 to regulate dendritic morphogenesis. We demonstrate that loss of Lhx2 causes a massive increase in Neurog2 expression, and that Neurog2 knockdown partially rescues the loss of Lhx2 phenotype. Our study uncovers novel LHX2 functions consistent with its temporally dynamic and diverse roles in development. TeaserThe mature architecture of a neuron is shaped by distinct genetic mechanisms that act in its mother cell and after it is born.

neuroscience↗

bioRxiv2023

Dual role of FOXG1 in regulating gliogenesis in the developing neocortex via the FGF signalling pathway.

In the developing vertebrate central nervous system, neurons and glia typically arise sequentially from common progenitors. Here, we report that the transcription factor Forkhead Box G1 (Foxg1) regulates gliogenesis in the mouse neocortex via distinct cell-autonomous roles in progenitors and in postmitotic neurons that regulate different aspects of the gliogenic FGF signalling pathway. We demonstrate that loss of Foxg1 in cortical progenitors at neurogenic stages causes premature astrogliogenesis. We identify a novel FOXG1 target, the pro-gliogenic FGF pathway component Fgfr3, that is suppressed by FOXG1 cell-autonomously to maintain neurogenesis. Furthermore, FOXG1 can also suppress premature astrogliogenesis triggered by the augmentation of FGF signalling. We identify a second novel function of FOXG1 in regulating the expression of gliogenic cues in newborn neocortical upper-layer neurons. Loss of FOXG1 in postmitotic neurons non-autonomously enhances gliogenesis in the progenitors via FGF signalling. These results fit well with the model that newborn neurons secrete cues that trigger progenitors to produce the next wave of cell types, astrocytes. If FGF signalling is attenuated in Foxg1 null progenitors, they progress to oligodendrocyte production. Therefore, loss of FOXG1 transitions the progenitor to a gliogenic state, producing either astrocytes or oligodendrocytes depending on FGF signalling levels. Our results uncover how FOXG1 integrates extrinsic signalling via the FGF pathway to regulate the sequential generation of neurons, astrocytes, and oligodendrocytes in the cerebral cortex.

neuroscience↗

bioRxiv2023

Using a modular massively parallel reporter assay to discover context-specific regulatory grammars in type 2 diabetes

Most genome-wide association signals for complex disease reside in the noncoding genome, where defining function is nontrivial. MPRAs (massively parallel reporter assays) offer a scalable means to identify functional regulatory elements, but are typically conducted without regard to cell type, pairing cloned fragments with a generic housekeeping promoter. To explore the context-sensitivity of MPRAs, we screened enhancer activity across a panel of nearly 12,000 198-bp fragments spanning over 300 type 2 diabetes- and metabolic trait-associated regions in the 832/13 rat insulinoma beta cell line, a relevant model of pancreatic beta cells. We explored these fragments context sensitivity by comparing their activities when placed up- or downstream of a reporter gene, and in combination with either a synthetic housekeeping promoter (SCP1) or a more biologically relevant promoter corresponding to the human insulin (INS) gene. We identified clear effects of MPRA construct design on enhancer activity. Specifically, a subset of fragments (n = 702/11,656) displayed positional bias, evenly distributed across up- and downstream preference. Promoter choice also influenced MPRA activity (n = 698/11,656), mostly biased towards the cell-specific INS promoter (73.4%). To identify sequence features associated with promoter preference, we used Lasso regression with 562 genomic annotations and discovered that fragments with INS promoter-biased activity are enriched for HNF1 motifs. HNF1 family transcription factors are key regulators of glucose metabolism disrupted in maturity onset diabetes of the young (MODY), suggesting genetic convergence between rare coding variants that cause MODY and common T2D-associated regulatory regions. We designed a follow-up MPRA containing HNF1 motif-enriched fragments and observed several instances where deletion or mutation of HNF1 motifs disrupted the INS promoter-biased enhancer activity, specifically in the beta cell model but not in a skeletal muscle cell line, another diabetes-relevant cell type. Together, our study suggests that cell-specific regulatory activity is partially influenced by enhancer-promoter compatibility and indicates that careful attention should be paid when designing MPRA libraries to capture context-specific regulatory processes at disease-associated genetic signals.

genomics↗

bioRxiv2023

Transmission of highly virulent CXCR4 tropic HIV-1 through the mucosal route in an individual with a wild-type CCR5 genotype

Nearly all transmitted/founder (T/F) HIV-1 are CCR5 (R5)-tropic. While previous evidence suggested that CXCR4 (X4)-tropic HIV-1 are transmissible, detection was not at the earliest stages of acute infection. Here, we identified an X4-tropic T/F HIV-1 in a participant in acute infection cohort. Coreceptor assays demonstrated that this T/F virus is strictly CXCR4 tropic. The participant experienced significantly faster CD4 depletion compared with R5 virus infected participants in the same cohort. Naive and central memory CD4 subsets declined faster than effector and transitional memory subsets. All CD4 subsets, including naive, were productively infected. Increased CD4+ T cell activation was observed over time. This X4-tropic T/F virus is resistant to broadly neutralizing antibodies (bNAbs) targeting V1/V2 and V3 regions. These findings demonstrate that X4-tropic HIV-1 is transmissible through the mucosal route in people with the wild-type CCR5 genotype and have implications for understanding the transmissibility and immunopathogenesis of X4-tropic HIV-1.

microbiology↗

bioRxiv2023

An architectural role of oskar mRNA in granule assembly

Ribonucleoprotein (RNP) granules are membraneless condensates that organize the intracellular space by compartmentalization of specific RNAs and proteins1. Studies have shown that RNA tunes the phase behavior of RNA binding proteins (RBPs)2-4, but the role of intermolecular RNA-RNA interactions in assembly of RNP granules in vivo remains less explored5-7. Here, we determine the role of a sequence-specific RNA-RNA kissing-loop interaction in assembly of mesoscale oskar RNP granules in the female Drosophila germline. A two-nucleotide mutation that disrupts kissing-loop-mediated oskar mRNA dimerization impairs condensate formation in vitro, oskar granule assembly in the developing oocyte - leading to defective posterior localization of the RNA, and abrogation of oskar-associated processing bodies (P-bodies) upon nutritional stress. This specific trans RNA-RNA interaction acts synergistically with the scaffold RBP, Bruno8, in driving condensate assembly. Our study highlights the architectural contribution of an mRNA and its specific secondary structure and tertiary interactions in formation of an RNP granule essential for embryonic development.

cell biology↗