Biology subjects

Moussa, M.

Publications and source records attributed to Moussa, M..

10 recordsLinked to original sources

bioRxiv2025

Access to germinal center IL-4 microniches drives tissue-divergence of IgE memoryresponses

Immunoglobulin E (IgE) drives allergic disease, yet how memory B cells (MBCs) reactivate to produce IgE, and how tissue localization shapes recall responses, remains unclear. Using mouse models of airborne exposure to house dust mites and Alternaria, we found that allergen sensitization generates lymphoid- and lung-resident MBCs. Upon allergen re-exposure, these populations followed distinct differentiation trajectories: lymph node MBCs engaged a germinal center (GC)-dependent pathway that generated both IgG1 and IgE plasma cells (PCs), whereas lung MBCs followed a GC-independent route producing mainly IgG1 PCs. GC re-entry granted MBCs access to an IL-4-rich microniche formed by Tfh cells, which was essential for IgE production. Disrupting GC re-entry, IL-4 signaling, or Tfh-derived IL-4 during recall markedly reduced allergen-specific IgE titers. These findings reveal a spatially and cytokine-restricted mechanism that confines IgE memory to lymphoid organs, positioning GC IL-4 microniches as anatomical safeguards against IgE production at barrier sites frequently exposed to environmental antigens.

immunology↗

bioRxiv2025

Tumor intrinsic regulation of PD-L1 and of interferon Type I via an SLC25A1-driven mitochondrial pathway, influences the anti-tumor immune response

Immune checkpoint inhibitors (ICIs) have transformed cancer therapy, but variable patient responses highlight the need to better regulators of immune sensitivity. Here, we identify the mitochondrial citrate carrier SLC25A1 as a determinant of anti-PD-L1 antibody therapy responsiveness through a dual regulation of type I interferon (IFN-I) signaling and of PD-L1 expression. SLC25A1 promotes a mitochondrial-to-nuclear retrograde signaling via cytosolic accumulation of mitochondrial DNA, activation of the cGAS-STAT1 axis, and establishment of a virus mimicry state that triggers the IFN-I response. This activation is enriched in cancer stem cell populations, consistent with the role for SLC25A1 in tumor stemness and therapy resistance. Moreover, SLC25A1 also regulates PD-L1 protein levels through a newly identified fumarate-Keap1-PD-L1 axis, whereby fumarate inhibits Keap1, leading to PD-L1 up-regulation. In vivo, tumors expressing high levels of SLC25A1 exhibit an inflammatory environment and increased sensitivity to PD-L1 blockade, but accelerated growth in the absence of anti-PD-L1 treatment. These findings position SLC25A1 as a novel regulator of mitochondrial-driven IFN-I signaling and PD-L1 stability, and suggest that SLC25A1 exploits PD-L1 to evade immune surveillance, while at the same time creating an intrinsic tumor vulnerability to checkpoint blockade. Thus, SLC25A1 may serve both as a biomarker of response and as a target to enhance the efficacy of immunotherapy.

cancer biology↗

bioRxiv2025

Mucosal B cell memory selection integrates tissue-specific microbial cues via the IgA BCR

B cells engender plasma cells (PCs) and memory B cells (MBCs) to combat recurrent pathogens. While B cell receptor (BCR) affinity dictates fate decisions in clonally-restricted set-ups, the driving factors in more complex systems remain unknown. Here, we show that memory selection during mucosal infection is imprinted by inherent cues from barrier tissues: lungs skew selection towards MBCs while the gut favors PC entry, even in response to the same pathogen. This divergence is linked to differential BCR isotype usage across barrier tissues rather than to affinity. In the gut, the commensal-induced TGF-{beta}-rich milieu promotes B cell class-switching to IgA. Consequently, the IgA BCR bias selection towards PCs, a process that is counteracted by its cytosolic tail domain. Overall, mucosal B cell selection integrates tissue-specific cues by strongly relying on BCR isotype usage rather than affinity, with implications for nasal and oral vaccine development. One sentence summaryDivergent B cell memory strategies evolved in lung and gut mucosa to counteract recurrent pathogens.

immunology↗

bioRxiv2025

TEAD inhibition alters the lung immune microenvironment and attenuates metastasis.

The Hippo pathway signaling mediated through YAP/TAZ, and the transcription factor TEAD is known to be involved in primary tumor progression. Here we report that novel TEAD inhibitors (iTEAD) cause a significant reduction in the outgrowth of lung metastases from triple negative breast cancer (TNBC) models mediated predominantly through changes in stromal immune signaling. TEAD inhibition did not affect the proliferation of TNBC cancer cells in vitro or the growth of the primary tumor in vivo. In normal mice that were treated with iTEAD in the absence of tumors, the lungs showed a decrease in pro-tumor inflammatory pathways. However, the IL12 signaling pathway was enhanced and its production from isolated lung tissue resident macrophages, but not bone marrow derived macrophages, was elevated. In syngeneic TNBC mouse models, inhibition of TEAD suppressed pro-tumor inflammation and the M2-like macrophage phenotype in lung tissues, and increased the infiltration of CD8+ T cells into the lung as well as Th1 CD4+ T cells, restoring an immune responsive microenvironment. iTEAD-treated T cells showed enhanced cytotoxicity and degranulation when co-cultured with cancer cells via increased IL-2 activity. Furthermore, TEAD inhibition or knockdown, enhanced T-cell macrophage crosstalk and anti-tumor activity in 3D tumorspheres which was reversed by IL12 neutralizing antibodies. Our data supports a multifaceted model of TEAD inhibition on the innate and adaptive immune cells as they respond to tumor cell signals and reveals an important stromal phenotype by which TEAD inhibitors could reverse immune suppression and eliminate seeded metastases in the lungs.

cancer biology↗

bioRxiv2024

FB5P-seq-mAbs: monoclonal antibody production from FB5P-seq libraries for integrative single-cell analysis of B cells

Parallel analysis of phenotype, transcriptome and antigen receptor sequence in single B cells is a useful method for tracking B cell activation and maturation during immune responses. However, in most cases, the specificity and affinity of the B cell antigen receptor cannot be inferred from its sequence. Antibody cloning and expression from single B cells is then required for functional assays. Here we propose a method that integrates FACS-based 5-end single-cell RNA sequencing (FB5P-seq) and monoclonal antibody cloning for integrative analysis of single B cells. Starting from a cell suspension, single B cells are FACS-sorted into 96-well plates for reverse transcription, cDNA barcoding and amplification. A fraction of the single-cell cDNA is used for preparing 5-end RNA-seq libraries that are sequenced for retrieving transcriptome-wide gene expression and paired BCR sequences. The archived cDNA of selected cells of interest is used as input for cloning heavy and light chain variable regions into antibody expression plasmid vectors. The corresponding monoclonal antibodies are produced by transient transfection of a eukaryotic producing cell line and purified for functional assays. We provide detailed step-by-step instructions and describe results obtained on ovalbumin-specific murine germinal center B cells after immunization. Our method is robust, flexible, cost-effective, and applicable to different B cell types and species. We anticipate it will be useful for mapping antigen specificity and affinity of rare B cell subsets characterized by defined gene expression and/or antigen receptor sequence.

immunology↗

bioRxiv2021

Viral infection engenders bona fide and bystander lung memory B cell subsets through permissive selection

Lung-resident memory B cells (MBCs) provide localized protection against reinfection in the respiratory airways. Currently, the biology of these cells remains largely unexplored. Here, we combined influenza and SARS-CoV-2 infection with fluorescent-reporter mice to identify MBCs regardless of antigen specificity. scRNA-seq analysis and confocal imaging revealed that two main transcriptionally distinct subsets of MBCs colonize the lung peribronchial niche after infection. These subsets arise from different progenitors and are both class-switched, somatically mutated and intrinsically biased in their differentiation fate towards plasma cells. Combined analysis of antigen-specificity and B cell receptor repertoire unveiled a highly permissive selection process that segregates these subsets into "bona fide" virus-specific MBCs and "bystander" MBCs with no apparent specificity for eliciting viruses. Thus, diverse transcriptional programs in MBCs are not linked to specific effector fates but rather to divergent strategies of the immune system to simultaneously provide rapid protection from reinfection while diversifying the initial B cell repertoire.

immunology↗

bioRxiv2021

SC1: A Tool for Interactive Web-Based Single Cell RNA-Seq Data Analysis

Single cell RNA-Seq (scRNA-Seq) is critical for studying cellular function and phenotypic heterogeneity as well as the development of tissues and tumors. Here, we present SC1 a web-based highly interactive scRNA-Seq data analysis tool publicly accessible at https://sc1.engr.uconn.edu. The tool presents an integrated workflow for scRNA-Seq analysis, implements a novel method of selecting informative genes based on Term-Frequency Inverse-Document-Frequency (TF-IDF) scores, and provides a broad range of methods for clustering, differential expression analysis, gene enrichment, interactive visualization, and cell cycle analysis. The tool integrates other single cell omics data modalities like TCR-Seq and supports several single cell sequencing technologies. In just a few steps, researchers can generate a comprehensive analysis and gain powerful insights from their scRNA-Seq data.

bioinformatics↗

bioRxiv2020

Immune Selection Pressure Contributes to Pancreatic Cancer Immune Evasion

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer death in the United States. Pancreatic tumors are minimally infiltrated by T cells and are largely refractory to immunotherapy. Accordingly, the role of T cell immunity in pancreatic cancer has been somewhat overlooked. Here, we hypothesized that immune evasion in pancreatic cancer is induced in response to T cell-based immune selection pressure, and that understanding how pancreatic tumors respond to immune attack may facilitate the development of more effective therapeutic strategies. We now provide the first evidence that T cell-dependent host immune responses induce a PDAC-derived myeloid mimicry phenomenon and stimulate immune evasion. mT3-2D cells derived from a Kras+/LSL-G12D; Trp53+/LSL-R172H; Pdx1-Cre (KPC) mouse model of pancreatic cancer were grown in immunocompetent and immunodeficient C57BL/6 mice, and analyzed to determine the impacts of adaptive immunity specifically on malignant epithelial cells as well as on whole tumors. We found that immune selection pressure, via signal transducer and activator of transcription 1 (STAT1), stimulates malignant epithelial pancreatic cells to induce the expression of genes typically expressed by myeloid cells and alters intratumoral immunosuppressive myeloid cell profiles. Targeting the Janus Kinase (JAK)/STAT signaling pathway using the FDA approved drug, ruxolitinib, overcomes these tumor-protective responses and improves anti-PD1 antibody therapeutic efficacy. These findings provide future directions for treatments that specifically disable this mechanism of resistance in PDAC.

cancer biology↗

bioRxiv2020

Evolution of cellular diversity in primary motor cortex of human, marmoset monkey, and mouse

The primary motor cortex (M1) is essential for voluntary fine motor control and is functionally conserved across mammals. Using high-throughput transcriptomic and epigenomic profiling of over 450,000 single nuclei in human, marmoset monkey, and mouse, we demonstrate a broadly conserved cellular makeup of this region, whose similarity mirrors evolutionary distance and is consistent between the transcriptome and epigenome. The core conserved molecular identity of neuronal and non-neuronal types allowed the generation of a cross-species consensus cell type classification and inference of conserved cell type properties across species. Despite overall conservation, many species specializations were apparent, including differences in cell type proportions, gene expression, DNA methylation, and chromatin state. Few cell type marker genes were conserved across species, providing a short list of candidate genes and regulatory mechanisms responsible for conserved features of homologous cell types, such as the GABAergic chandelier cells. This consensus transcriptomic classification allowed the Patch-seq identification of layer 5 (L5) corticospinal Betz cells in non-human primate and human and characterization of their highly specialized physiology and anatomy. These findings highlight the robust molecular underpinnings of cell type diversity in M1 across mammals and point to the genes and regulatory pathways responsible for the functional identity of cell types and their species-specific adaptations.

neuroscience↗

bioRxiv2018

Locality Sensitive Imputation for Single-Cell RNA-Seq Data

One of the most notable challenges in single cell RNA-Seq data analysis is the so called drop-out effect, where only a fraction of the transcriptome of each cell is captured. The random nature of drop-outs, however, makes it possible to consider imputation methods as means of correcting for drop-outs. In this paper we study some existing scRNA-Seq imputation methods and propose a novel iterative imputation approach based on efficiently computing highly similar cells. We then present the results of a comprehensive assessment of existing and proposed methods on real scRNA-Seq datasets with varying per cell sequencing depth.

bioinformatics↗