The incidence of autoimmune diseases, like Systemic Lupus Erythematosus (SLE) or Systemic Sclerosis (SSc) is markedly increased in women and in 47 XXY Klinefelter syndrome men (KS), as compared to 46 XY men, possibly in relationship with differences in X chromosome dosage. While in women, one of the two X chromosomes is inactivated (XCI), some genes can escape XCI, leading to increased expression of some X-linked genes. TLR7 is an important activator of the immune system, its gene is located on the X-chromosome and when expressed at double dose Tlr7 is sufficient to trigger autoimmunity in mice. We have recently demonstrated that TLR7 evades silencing in a facultative manner in a significant proportion of immune cells from healthy women, and KS males, resulting in enhanced immune responses, particularly in B cells. B cells expressing TLR7 biallelically (BiA7 B cells) are more responsive than monoallelic cells at specific checkpoints of B cell differentiation, when activated through TLR7, but not TLR9 (Sci. Immunol 2018, PMID:29374079). This observation supports the hypothesis that TLR7 overexpression through biallelism is a candidate contributor to the risk of SLE, in women and KS men. Our working hypothesis is that the X-linked genetic risk to autoimmunity is an evolutionary consequence of positive selection for favorable immune response to infection. Evaluating the origin and defining the mechanisms leading to the development and maintenance of BiA7 B cells as well as their direct contribution to development of lupus-like syndrome will be the focus of the current proposal. Using mouse models, we will address the functional consequences of Tlr7 expression from the inactive X chromosome in naïve B cells, and their direct contribution to the germinal center responses in mouse models. In parallel, we will also assess the relationship between BiA7 cells and the development of dysregulated immune responses involved in disease pathogenesis in SLE, with a particular focus on the “age(autoimmunity)-associated B cell” (ABC) subset, emerging as key cellular source of autoantibodies in SLE, in humans and mice. We will validate our observation in immune cells from SLE women and also test the hypothesis that genetic factors associated with disease or the chronic autoinflammatory conditions caused by SLE or SSc may have an impact on the status of “escapee” of TLR7 and others X-linked disease-associated candidate genes. This project will provide an unprecedented dissection of the contribution of XCI escape mechanisms on the functional responses of B cells, but also on the nature of the mechanism underlying the enhanced female susceptibility to autoimmune diseases, and therefore may open avenues for the development of novel therapeutics in rheumatic diseases.

CD4 T lymphocytes are highly efficient at protecting the host against a wide variety of endogenous and exogenous dangers, comprising tumors, viruses, bacteria and parasites. Their efficiency comes at least in part from their ability to adapt their phenotype and function to the nature of the threat. T lymphocytes indeed mobilize distinct gene expression programs which coordinate the acquisition of lineage-specific and danger-adapted phenotypes and functions. Naïve CD4 T cells are thus able to differentiate into distinct Thelper (“Th”) lymphocyte populations, including the so-called Th1, Th2, Th17 and Treg cells. Interplay of transcription factors and epigenetic mechanisms have a causal role in the regulation of Th lymphocytes gene expression programs. Interplay of transcription factors and epigenetic mechanisms, such as DNA methylation or post-translational histone modifications, have a causal role in the regulation of Th gene expression programs. Preliminary data from our group and emerging evidence from the literature suggest another layer of complexity in Th commitment and function as a result of epitranscriptomic modifications, i.e. dynamic chemical modifications of transcripts. It emerged as a new fundamental conserved mechanism involved in the control of cell differentiation and homeostasis. Half of known RNA modifications have already been linked to human diseases, including immune related diseases. Whereas several studies characterized an essential role of epitranscriptomic modifications in the regulation of different aspects of the immune system, the characterization of the majority of epitranscriptomic actors in Th subsets is still poorly understood, at least in part due to the lack of epitranscriptomic adapted study tools. Recently emerged a new method allowing accurate detection of all RNA modifications at single-base level in native full-length RNA transcripts using third-generation sequencing (Oxford Nanopore Technologies). The main objective of this project is to understand the respective role of RNA modifications related enzymes in Th subsets by combining in vitro and in vivo approaches as well as Nanopore sequencing. Extend our knowledge of the epitranscriptomic regulation of gene expression in Th cells could ultimately provide novel insights into the pathogenesis of autoimmune disorders and potential targets for epitranscriptomic therapy.

Cutaneous lesions are associated with the inability to reform a protective dermis and the formation of a fibrotic scar. Using an original mouse model of skin injury where regeneration takes place in the center of the lesion while the periphery remains fibrotic, we have demonstrated that mesenchymal stromal c cells (i.e. fibroblasts) activate a specific transcriptomic program and different functions depending on their location in the injury site. More recently, we have shown that neutrophils, more particularly immature neutrophils, upstream of the activation of fibroblasts, also improve the regeneration of the dermis and hair follicles. Our data as well as recent work in the literature show that the sensory nerves innervating the skin (i.e. nociceptors) are involved in maintaining skin homeostasis upon injury, by controlling the resident and recruited immune cells, including neutrophils and that they may also be involved in tissue regeneration processes. In our NEUTROPHEAL project, we propose to study the interactions between neutrophils, nociceptors and fibroblasts during the skin wound healing process. By combining our expertise in dermatology, neuroimmunology and mesenchymal stromal cells, we aim to understand how the neutrophils/nociceptors/fibroblasts triad communicate with each other in order to improve tissue regeneration at the expense of fibrosis. Ultimately, we hope that this integrative study will reveal treatments that could benefit millions of patients suffering from serious skin lesions such as burns and skin trauma.

Atopic dermatitis (AD) and Psoriasis (Pso) are frequent chronic inflammatory skin conditions that affect around 7% and 3% of adults, respectively. These two diseases are driven by different (almost antagonist) immune responses, i.e a type 2 immune response for AD and a type 1/17 immune response for Pso. Recent pre-clinical studies have suggested that nociceptive sensory neurons (nociceptors – which transmit itch and pain messages) could actively participate in the development of the inflammatory response in both diseases, but their precise role is still elusive. In this study, we will combine expertise in neuro-immunology, transcriptomic and chemogenetic to study the role played by nociceptors in chronic mouse models of AD and Pso. This work should shed new lights on the plasticity and function of skin-projecting nociceptors in two important dermatoses and help to identify new “neuro-immune-oriented” therapeutic opportunities.

Tissue-resident memory cells (Trm) are a subset of memory T cells that stably reside in non-lymphoid tissues, where they provide immediate protection against pathogen infection. Trm have also been shown to sustain inflammation in various chronic and autoimmune conditions. Indeed, our recent published study demonstrated that the development of autoreactive Trm could be an important mechanism in the chronic course of central nervous system (CNS) autoimmune diseases such as multiple sclerosis and paraneoplasic neurological disorders. Although some cues driving CD8 Trm differentiation and/or maintenance have been recently described the exact pathways mobilised to promote their long-term persistence in the CNS remain unknown. To gain a better insight into the molecular mechanisms underpinning Trm persistence during chronic CNS pathologies, we made use of a model of latent infection with the Toxoplasma gondii parasite and a mouse model of neuroral autoimmunity mediated by autoreactive CD8 T cells. Our single-cell RNA-seq analyses of brain CD8 Trm cells showed that specific prosurvival molecules from the Bcl2-protein family and the IFNgR1 signalling pathway were induced in Trm cells compared to their recirculating counterparts. Our preliminary data suggested that the inhibition of these molecules/pathways in CD8 T cells using shRNA and/or Crispr-cas9 technology led to a strong defect in Trm maintenance in the brain. Based on these preliminary findings, we postulate that brain Trm rely on specific prosurvival molecules from the mitochondrial apoptotic pathway and on the IFNgR1-signalling pathway for their long-term maintenance within the CNS. We are now aiming to (i) determine the phenotypic and the physiopathological consequences of the inhibition of pro-survival molecules of the Bcl2 family in Trm during autoimmunity and persistent pathogen infection of the CNS, (ii) elucidate the molecular mechanisms underpinning the IFNgR1-signalling mediated persistence of brain Trm in these two models of CNS inflammation, and (iii) validate in human brain Trm the relevance of these pathways using tissue samples from patients with infectious or autoimmune CNS diseases. Overall, this project will provide a better understanding of the mechanisms underpinning the survival/retention of Trm within the CNS. Therefore, it represents an important step for the design of new therapies against chronic neuroinflammatory diseases, which would aim to modulate Trm density in the CNS, either to promote their potential beneficial persistence during a chronic pathogen infection, or conversely to decrease their survival in order to reduce chronic inflammation.