Biology subjects

Behmoaras, J.

Publications and source records attributed to Behmoaras, J..

9 recordsLinked to original sources

bioRxiv2026

A Cross-Species Systems Genetics Framework Identifies Causal Genes in Diabetic Nephropathy

Diabetic nephropathy (DN) is the leading cause of kidney failure in the developed world, but the genetic architecture of DN susceptibility is not well characterised. Here we apply a systems genetics approach in a mouse model of DN to discover novel QTLs for clinically relevant phenotypes including albuminuria, glomerulosclerosis, and macrophage infiltration. For context and prioritisation, we combined single-cell-transcriptomics-guided pQTL and eQTL mapping with cell-type-specific co-expression networks, identifying 192 candidate pGenes for albuminuria. While many were novel, 27% had prior genetic associations, and 40% were validated in a human diabetic cohort. Twelve genes belong to a podocyte network enriched for human GWAS signals. Among those, functional significance of the E3 ubiquitin ligases DCAF6 and ZNRF2 was confirmed by knockdown in Drosophila nephrocytes. Our systems genetics approach identified DN susceptibility genes previously validated in human GWAS while uncovering potential new genes and pathways that could be exploited for risk stratification and therapeutics development.

systems biology↗

bioRxiv2023

Fatty acid synthesis promotes inflammasome activation through NLRP3 palmitoylation.

Inflammasomes are multi-protein complexes assembled by NOD-like receptor (NLR) family of proteins, which play critical roles in infectious, inflammatory and metabolic diseases. The assembly of the NLRP3 inflammasome is triggered upon recognition of an apt stimulus by the sensor protein, resulting in binding to pro-caspase-1 via the adaptor protein ASC. Inflammasome activation results in the maturation of the precursor forms of cytokines IL-1{beta} and IL-18, along with caspase-1-dependent pyroptosis, a pro-inflammatory form of cell death. Emerging evidence suggests the involvement of lipid metabolism in inflammasome activation; however, the precise mechanisms by which lipids regulate the NLRP3 inflammasome remain ambiguous. A multi-enzyme protein, fatty acid synthase (FASN) is a central regulator of lipid metabolism partaking an essential role in fatty acid biosynthesis pathway by catalysing the production of palmitic acid. Palmitic acid acts as a precursor to long-chain fatty acids and additionally regulates cellular functions by palmitoylation, a process in which palmitate is reversibly added to cysteine residues of target proteins, modifying protein localization and function. Here, we undertook a pharmacological approach to investigate the roles of fatty acid biosynthetic pathway in NLRP3 inflammasome activation. Our results demonstrated that inhibition of FASN in primary mouse and human macrophages abrogates the activation of the NLRP3 inflammasome, resulting in blunted caspase-1 activation. Furthermore, this phenomenon relied on protein palmitoylation as in vitro and in vivo abrogation of palmitoylation similarly reduced NLRP3 activation, which could be restored by exogenously supplementing palmitate in cultured cells. Consequently, an acyl biotin exchange assay corroborated NLRP3 palmitoylation. Notably, activation of the dsDNA sensing AIM2 inflammasome remained unaltered when either FASN or palmitoylation was blocked. These results therefore highlight the pivotal role of FASN and palmitoylation, shedding new mechanistic insights into the activation of the NLRP3 inflammasome.

immunology↗

bioRxiv2023

WWP2 MEDIATES THE METABOLIC REPROGRAMMING OF RENAL MYOFIBROBLASTS TO PROMOTE KIDNEY FIBROSIS

Renal fibrosis is a common pathological endpoint in chronic kidney disease (CKD) that is challenging to reverse. Although myofibroblasts are mainly responsible for the accumulation of a fibrillar collagen-rich extracellular matrix (ECM) in fibrotic kidney, recent studies have unveiled their diversity in terms of proliferative and fibrotic characteristics. This diversity could be linked with the existence of different metabolic states, and myofibroblast metabolic reprogramming may contribute to the pathogenesis and progression of renal fibrosis. Here, we reveal an unexpected role of the E3 ubiquitin-protein ligase WWP2 in the metabolic reprogramming of myofibroblasts during renal fibrosis. The tubulointerstitial expression of WWP2 contributes to the progression of fibrosis in CKD patients, and in pre-clinical murine models of CKD. WWP2 deficiency increases fatty acid oxidation and activates the pentose phosphate pathway, boosting mitochondrial respiration at the expense of glycolysis. This concurrently promotes myofibroblast proliferation and halts pro-fibrotic activation, reducing the severity of kidney fibrosis. Mechanistically, WWP2 suppresses the transcription of PGC-1, a metabolic mediator shaping myofibroblast fibrotic response. Pharmacological interventions targeting PGC-1 reverse the effects of WWP2 on fibrotic myofibroblasts. These findings demonstrate the influence of WWP2 on essential metabolic pathways involved in fibrogenesis, uncovering the WWP2-PGC-1 axis that orchestrates the metabolic reprogramming of myofibroblasts during renal fibrosis. Our study presents a potential novel target for therapeutic intervention in the treatment of chronic kidney disease. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=177 HEIGHT=200 SRC="FIGDIR/small/554242v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@1847ffeorg.highwire.dtl.DTLVardef@1ef029aorg.highwire.dtl.DTLVardef@93e0f1org.highwire.dtl.DTLVardef@950d49_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIWWP2 expression is elevated in the tubulointerstitium of fibrotic kidneys and contributes to CKD pathogenesis and progression. C_LIO_LIWWP2 uncouples the pro-fibrotic activation and cell proliferation in renal myofibroblasts. C_LIO_LIWWP2 controls mitochondrial respiration in renal myofibroblasts through the metabolic regulator PGC-1 C_LIO_LIMyofibroblast metabolic reprogramming mediates the effect of WWP2 on fibrotic myofibroblasts. C_LI

cell biology↗

bioRxiv2023

Comparative analysis of single-cell RNA sequencing methods with and without sample multiplexing

Single-cell RNA sequencing (scRNA-seq) has emerged as a powerful technique for investigating biological heterogeneity at the single-cell level in human systems and model organisms. Recent advances in scRNA-seq have enabled the pooling of cells from multiple samples into single libraries, thereby increasing sample throughput while reducing technical batch effects, library preparation time, and the overall cost. However, a comparative analysis of scRNA-seq methods with and without sample multiplexing is lacking. In this study, we benchmarked methods from two representative platforms: Parse Biosciences (Parse; with sample multiplexing) and 10X Genomics (10x; without sample multiplexing). By using peripheral blood mononuclear cells (PBMCs) obtained from two healthy individuals, we demonstrate that demultiplexed scRNA-seq data obtained from Parse showed similar cell type frequencies compared to 10X data where samples are not multiplexed. Despite a relatively lower library and cell capture efficiencies, Parse can detect rare cell types (e.g. plasmablasts and dendritic cells) which is likely due to its relatively higher sensitivity in gene detection. Moreover, comparative analysis of transcript quantification between the two platforms revealed platform-specific distributions of gene length and GC content. These results offer guidance for researchers in designing high-throughput scRNA-seq studies.

genomics↗

bioRxiv2023

BCAT1 inhibition affects CD8+ T cell activation, exhaustion, and tumoral immunity by altering iron homeostasis

The present study explores the role of the cytosolic branched chain amino acid aminotransferase (BCAT1) in CD8+ T cell activation, in general, and tumor immunity, in particular, and identifies a non-canonical function of the protein in iron homeostasis. Pharmacologic inhibition of BCAT1 using the novel drug ERG245 abrogates the effector functions of CD8+ T cells in vitro and metabolically reprograms the cells towards increased OXPHOS. In vivo, it suppresses activation of CD8+ T cells in DSS colitis leading to improved disease outcomes. Remarkably, withdrawal of BCAT1 inhibition further amplifies OXPHOS and gives rise to CD8+ T cells with increased cytotoxicity in vitro and in vivo. When combined with an anti-PD-1 treatment, temporal BCAT1 inhibition dramatically increases anti-PD-1 efficacy inducing complete and durable tumor regressions in the moderately immunogenic CT26 tumor model. Single cell RNA-seq data link expression of Bcat genes to exhausted T cells within the tumor microenvironment of human cancer patients, whereas in vitro assays indicate that BCAT1 inhibition partially prevents the adoption of a terminally exhausted phenotype by CD8+ T cells. We propose BCAT1 as a target for cancer combinatory therapies. SIGNIFICANCEThe study explores for the first time the role of BCAT1 in CD8+ T cell activation and proposes novel strategies for using BCAT1 inhibitors in cancer and beyond. It demonstrates that BCAT1 exerts its function without significantly altering branched chain amino acid (BCAA) levels through a mechanism that controls iron homeostasis, a novel non-canonical mechanism of action, and implicates BCAT1 in the adoption of an exhausted phenotype by T cells found in human cancers. While the majority of metabolic drugs temper OXPHOS, it demonstrates that an agent that increases OXPHOS in CD8+ T cells can be used successfully as an immune-oncology drug.

immunology↗

bioRxiv2022

Systems Level Identification Of A Matrisome-Associated Macrophage Polarization State In Multi-Organ Fibrosis

Tissue fibrosis affects multiple organs and involves a master-regulatory role of macrophages which respond to an initial inflammatory insult common in all forms of fibrosis. The recently unraveled multi-organ heterogeneity of macrophages in healthy and fibrotic human disease suggest that tissue resident macrophages, expressing osteopontin (SPP1), associate with lung and liver fibrosis. However, the conservation of this SPP1+ macrophage population across different tissues, and its specificity to fibrotic diseases with different etiologies remain unclear. Integrating 13 single cell RNA-sequencing datasets to profile 225,985 tissue macrophages from healthy and fibrotic heart, lung, liver, kidney, skin and endometrium, we extended the association of SPP1+ macrophages with fibrosis to all these tissues. We also identified a subpopulation expressing matrisome-associated genes (e.g., matrix metalloproteinases and their tissue inhibitors), functionally enriched for ECM remodeling and cell metabolism, representative of a matrisome-associated macrophage (MAM) polarization state within SPP1+ macrophages. Importantly, the MAM polarization state follows a differentiation trajectory from SPP1+ macrophages, which was conserved across all fibrotic tissues and driven by NFATC1 and HIVEP3 regulons. Unlike SPP1+ macrophages, the MAM polarization state shows a positive association with ageing in mice and humans, and across multiple tissues during homeostasis. These results suggest an advanced, age-dependent polarization state of SPP1+ macrophages in fibrotic tissues as a result of prolonged inflammatory cues within each tissue microenvironment.

systems biology↗

bioRxiv2022

Multinucleation resets human macrophages for specialized functions at the expense of mononuclear phagocyte identity

Macrophages undergo plasma membrane fusion and cell multinucleation to form multinucleated giant cells (MGCs) such as osteoclasts in bone, Langhans giant cells (LGCs) as part of granulomas or foreign-body giant cells (FBGCs) in reaction to exogenous material. While osteoclast multinucleation is a prerequisite for vertebrate bone homeostasis, the effector function resulting from LGC and FBGC multinucleation is less well-defined. More generally, how multinucleation per se contributes to functional specialization of mature mononuclear macrophages remains poorly understood in humans. Here, we integrated comparative transcriptomics with functional assays in purified mature mononuclear and multinucleated human osteoclasts, LGCs and FBGCs. Strikingly, in all three types of MGCs, multinucleation causes a pronounced down-regulation of mononuclear phagocyte identity. We show enhanced lysosome-mediated intracellular iron homeostasis promoting MGC formation. The transition from mononuclear to multinuclear state is accompanied by cell specialization specific to each polykaryon. Enhanced phagocytic and mitochondrial function associate with FBGCs and osteoclasts, respectively. Moreover, only B7-H3 (CD276)-expressing human LGCs can form granuloma-like clusters in vitro, suggesting that LGC multinucleation potentiates T cell activation. These findings demonstrate how cell-cell fusion and multinucleation reset human macrophage identity as part of an advanced maturation step that confers MGC-specific functionality.

cell biology↗

bioRxiv2020

A trans-eQTL network regulates osteoclast multinucleation and bone mass

Functional characterisation of cell-type specific regulatory networks is key to establish a causal link between genetic variation and phenotype. The osteoclast offers a unique model for interrogating the contribution of co-regulated genes to in vivo phenotype as its multinucleation and resorption activities determine quantifiable skeletal traits. Here we took advantage of a trans-regulated gene network (MMnet, macrophage multinucleation network) which we found to be significantly enriched for GWAS variants associated with bone-related phenotypes. We found that the network hub gene Bcat1 and seven other co-regulated MMnet genes out of 13, regulate bone function. Specifically, global (Pik3cb-/-, Atp8b2+/-, Igsf8-/-, Eml1-/-, Appl2-/-, Deptor-/-) and myeloid-specific Slc40a1{Delta}LysMCre knockout mice displayed abnormal bone phenotypes. We report antagonizing effects of MMnet genes on bone mass in mice and osteoclast multinucleation/resorption in humans with strong correlation between the two. These results identify MMnet as a functionally conserved network that regulates osteoclast fusion and bone mass. Impact statementWe took advantage of the osteoclast whose multinucleation properties correlate with bone mass. We show that a trans-regulated gene network (MMnet) controls skeletal homeostasis through osteoclast multinucleation and function.

cell biology↗

bioRxiv2017

Deferiprone, an iron chelator, is preventive and therapeutic in experimental crescentic glomerulonephritis

Crescentic glomerulonephritis represents the most severe form of antibody-mediated glomerulonephritis. It is an important cause of renal dysfunction worldwide and there is a need for more effective treatment. Deferiprone, an orally active iron chelator, is widely used in patients with thalassemia. Here we present the preventive and therapeutic effects of deferiprone in experimental crescentic glomerulonephritis. Nephrotoxic nephritis was induced in Wistar Kyoto rats, and preventive treatment with deferiprone substantially lowered glomerular crescent formation by 84%, with 70% reduction in proteinuria. In established glomerulonephritis, deferiprone treatment effectively halted glomerular inflammation, reversed progression of proteinuria, and prevented deterioration of renal function. Deferiprone reduced glomerular inflammatory cell proliferation in vivo. It was internalised by monocyte/macrophages and inhibited their proliferation in vitro, without showing cellular toxicity. Interestingly, deferiprone showed a neutralizing effect on superoxide anions, and prevented the expression of monocyte chemoattractant protein-1 and matrix metalloproteinase 9, 12 and 14, by primary macrophages. These results suggest that deferiprone partly exerts its renal protective effect through inhibition of monocyte/macrophage proliferation and function by iron-chelating and anti-oxidant properties, respectively. We conclude that deferiprone is an effective treatment in a severe and reproducible model of antibody-mediated glomerular inflammation that resembles human crescentic glomerulonephritis, indicating its therapeutic potential.

immunology↗