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- Aoun, Mike
(author)
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Positional cloning of polymorphic loci that control autoreactive T cells
- 2021
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Doctoral thesis (other academic/artistic)abstract
- Autoimmune diseases are expensive diseases, both financially and socially, because they are in most cases life long and require a long-lasting treatment. They can also be life threatening, as they are among top 10 causes of death in women and therefore, they represent a serious clinical problem and require careful medical management. There is an autoimmune disease for every system or organ and the one discussed mainly in this thesis is rheumatoid arthritis (RA). RA is the most common autoimmune disease and primarily affects the joints. It is more prevalent in women than man (3:1) and known to have a strong genetic component for its predisposition. Animal models offer an attractive strategy to study the underlying arthritis-associated genes under a controlled environment. Forward genetics is an approach to dissect genes that regulate a desired trait, from phenotype to genotype. However, this method often fails to pinpoint a single gene but identifies sized genetic fragments that harbor several point mutations inside or outside the genes. These single nucleotide polymorphisms or SNPs in short could have a dramatic effect on the transcription or translation of the gene. Once the arthritis-associated SNP is identified and the gene of interest is positionally cloned, the search for a mechanism of action commences. All the studies included in this thesis have forward genetics as a common denominator except the last manuscript. In Study I, we positionally cloned the arthritis regulating gene in congenic rats that derive from a cross between an arthritis susceptible (DA) and resistant (E3) inbred strains. We found that a SNP in the second exon of clec4b caused the introduction of a stop codon and lead to the abrogation of the coded protein Dcar. Arthritis susceptibility increased drastically because of this loss of function mutation and influenced profoundly T cells which are the major driving force of induced arthritis models in rats. In Study II, a natural polymorphism in the promoter of Vdr was cloned in congenic mice and was found to be overexpressed selectively in T cells without any calcemic abnormalities. Consequently, antigen-specific T cell responses were enhanced, and autoimmunity was worsened. In Study III, we set out to investigate the interaction between the two most significant arthritis QTL in rats that were previously positionally cloned, Ncf1 and Clec4b. We found that Dcar and Ncf1 regulate in concert arthritis severity and their expression on neutrophils influenced their capacity to produce reactive oxygen species. In Study IV, we ventured to answer one of immunology’s longstanding question; are antigen-specific B cells positively selected? We show that indeed collagen type-II (Col2) specific B cells are positively selected and could be detected in transgenic mice, wild type mice and inbred rats. Moreover, we cloned the B cell receptor from human blood donor, expressed the antibody and validated its specificity to Col2. Moreover, we demonstrate that these Col2-specific B cells inhibit arthritis by inducing Col2-specific regulatory T cells. The data illustrated in this thesis confirm in part, the importance of animal models in deciphering disease regulating genes and highlight the implication of antigen specific B cells in a prominent autoimmune disease.
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| 2. |
- He, Yibo, et al.
(author)
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A subset of antibodies targeting citrullinated proteins confers protection from rheumatoid arthritis.
- 2023
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In: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 14:1
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Journal article (peer-reviewed)abstract
- Although elevated levels of anti-citrullinated protein antibodies (ACPAs) are a hallmark of rheumatoid arthritis (RA), the in vivo functions of these antibodies remain unclear. Here, we have expressed monoclonal ACPAs derived from patients with RA, and analyzed their functions in mice, as well as their specificities. None of the ACPAs showed arthritogenicity nor induced pain-associated behavior in mice. However, one of the antibodies, clone E4, protected mice from antibody-induced arthritis. E4 showed a binding pattern restricted to skin, macrophages and dendritic cells in lymphoid tissue, and cartilage derived from mouse and human arthritic joints. Proteomic analysis confirmed that E4 strongly binds to macrophages and certainRA synovial fluid proteins such as α-enolase. The protective effect of E4 was epitope-specific and dependent on the interaction between E4-citrullinated α-enolase immune complexes with FCGR2B on macrophages, resulting in increased IL-10 secretion and reduced osteoclastogenesis. These findings suggest that a subset of ACPAs have therapeutic potential in RA.
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| 3. |
- Sabatier, Pierre, et al.
(author)
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An integrative proteomics method identifies a regulator of translation during stem cell maintenance and differentiation
- 2021
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In: Nature Communications. - : Springer Nature. - 2041-1723. ; 12
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Journal article (peer-reviewed)abstract
- To characterize molecular changes during cell type transitions, the authors develop a method to simultaneously measure protein expression and thermal stability changes. They apply this approach to study differences between human pluripotent stem cells, their progenies, parental and allogeneic cells. Detailed characterization of cell type transitions is essential for cell biology in general and particularly for the development of stem cell-based therapies in regenerative medicine. To systematically study such transitions, we introduce a method that simultaneously measures protein expression and thermal stability changes in cells and provide the web-based visualization tool ProteoTracker. We apply our method to study differences between human pluripotent stem cells and several cell types including their parental cell line and differentiated progeny. We detect alterations of protein properties in numerous cellular pathways and components including ribosome biogenesis and demonstrate that modulation of ribosome maturation through SBDS protein can be helpful for manipulating cell stemness in vitro. Using our integrative proteomics approach and the web-based tool, we uncover a molecular basis for the uncoupling of robust transcription from parsimonious translation in stem cells and propose a method for maintaining pluripotency in vitro.
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