Replacement of Iγ3 germ-line promoter by Iγ1 inhibits class-switch recombination to IgG3

Class-switch recombination (CSR) enables IgM-producing B cells to switch to the production of IgG, IgE, and IgA. The process requires germ-line (GL) transcription that initiates from promoters upstream of switch (S) sequences and is regulated by the 3′ regulatory region (3′RR) located downstream of the Ig heavy chain (IgH) locus. How the 3′RR effect its long-range activation is presently unclear. We generated a mouse line in which Iγ3 GL promoter was replaced by Iγ1. We found that GL transcription could initiate from the inserted Iγ1 promoter and was induced by increased concentrations of IL-4 and that the transcripts were normally spliced. However, when compared with GL transcripts derived from the endogenous Iγ1 promoter in the same stimulation conditions, those from the inserted Iγ1 promoter were less abundant. CSR to Cγ3 was abrogated both in vivo and in vitro. The results strongly suggest that the endogenous Iγ1 promoter insulates the inserted Iγ1 from the long-range activating effect of the 3′RR. The implications of our findings are discussed in light of the prominent models of long-distance activation in complex loci

Cardiac Troponin-I (cTnI) a Biomarker of Cardiac Injuries Induced by Doxorubicin Alone and in Combination with Ciprofloxacin, Following Acute and Chronic Dose Protocol in Sprague Dawley Rats

The present study investigates the release of cardiac troponin-I (cTnI) as a biomarker of cardiac injuries induced by doxorubicin (Doxo) alone and along with ciprofloxacin (Cipro), following acute and chronic dose protocol in Sprague Dawley rats. In chronic protocol, rats were given multiple intra-peritoneal (i.p) injections of Doxo (1 or 2.5 mg kg(-1)) alone or in combination with Cipro (20 mg kg(-1) daily) and a placebo control. Whereas in acute protocol, rats were subjected to receive single i.p. injection of Doxo (6 or 15 mg kg(-1)) alone or along with Cipro (20 mg kg(-1)) and placebo treatment with saline (control). The plasma levels of cTnI were measured by using Enzyme-linked Immuno Sorbent Assay (ELISA) technique. All the treated groups, following acute or chronic dose protocol showed significant increase in cTnI plasma level from 137-248% in comparison to control (p<0.0001). The cTnI plasma levels increased in dose dependent manner after following acute and chronic dose protocol. The difference between two doses following chronic (1 mg kg(-1) vs. 2.5 mg kg(-1)) and acute (6 vs. 15 mg kg(-1)) administration was 34.6 and 31.5%, respectively. Results of this investigation suggest that Doxo alone and in combination with Cipro from both the chronic and acute groups showed cardio-toxicity (release of cTnI). To our knowledge this is the first description towards Doxo-Cipro is induced cardiotoxicity and could be a bridge between preclinical and clinical practice for physicians in making an expert opinion dealing with above mentioned group

IgH 3’ regulatory region increases ectopic class switch recombination

International audienceDNA lesions inflicted by activation-induced deaminase (AID) instrumentally initiate the processes reshaping immunoglobulin genes in mature B-cells, from local somatic hypermutation (SHM) to junctions of distant breaks during class switch recombination (CSR). It remains incompletely understood how these divergent outcomes of AID attacks are differentially and temporally focused, with CSR strictly occurring in the Ig heavy chain ( IgH ) locus while SHM concentrates on rearranged V(D)J regions in the IgH and Ig light chain loci. In the IgH locus, disruption of either the 3’Regulatory Region (3’RR) super-enhancer or of switch (S) regions preceding constant genes, profoundly affects CSR. Reciprocally, we now examined if these elements are sufficient to induce CSR in a synthetic locus based on the Igκ locus backbone. Addition of a surrogate “core 3’RR” (c3’RR) and of a pair of transcribed and spliced Switch regions, together with a reporter system for “κ-CSR” yielded a switchable Igκ locus. While the c3’RR stimulated SHM at S regions, it also lowered the local SHM threshold necessary for switch recombination to occur. The 3’RR thus both helps recruit AID to initiate DNA lesions, but then also promotes their resolution through long-distance synapses and recombination following double-strand breaks

Sequence Dependence of Chromosomal R-Loops at the Immunoglobulin Heavy-Chain Sμ Class Switch Region▿ †

The mechanism by which the cytidine deaminase activation-induced deaminase (AID) acts at immunoglobulin heavy-chain class switch regions during mammalian class switch recombination (CSR) remains unclear. R-loops have been proposed as a basis for this targeting. Here, we show that the difference between various forms of the Sμ locus that can or cannot undergo CSR correlates well with the locations and detectability of R-loops. The Sμ R-loops can initiate hundreds of base pairs upstream of the core repeat switch regions, and the area where the R-loops initiate corresponds to the zone where the AID mutation frequency begins to rise, despite a constant density of WRC sites in this region. The frequency of R-loops is 1 in 25 alleles, regardless of the presence of the core Sμ repeats, again consistent with the initiation of most R-loops upstream of the core repeats. These findings explain the surprisingly high levels of residual CSR in B cells from mice lacking the core Sμ repeats but the marked reduction in CSR in mice with deletions of the region upstream of the core Sμ repeats. These studies also provide the first analysis of how R-loop formation in the eukaryotic chromosome depends on the DNA sequence

IgA Structure Variations Associate with Immune Stimulations and IgA Mesangial Deposition

This deposit is composed by a publication in which the IGC's authors have had the role of collaboration (it's a collaboration publication). This type of deposit in ARCA is in restrictedAccess (it can't be in open access to the public), and can only be accessed by two ways: either by requesting a legal copy from the author (the email contact present in this deposit) or by visiting the following link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5004660/This publication hasn't any creative commons license associated.Further funders are not indicated in the document.IgA1 mesangial deposition is the hallmark of IgA nephropathy and Henoch-Schönlein purpura, the onset of which often follows infections. Deposited IgA has been reported as polymeric, J chain associated, and often, hypogalactosylated but with no information concerning the influence of the IgA repertoire or the link between immune stimuli and IgA structure. We explored these issues in the α1KI mouse model, which produces polyclonal human IgA1 prone to mesangial deposition. Compared with mice challenged by a conventional environment, mice in a specific pathogen-free environment had less IgA deposition. However, serum IgA of specific pathogen-free mice showed more galactosylation and much lower polymerization. Notably, wild-type, α1KI, and even J chain-deficient mice showed increased polymeric serum IgA on exposure to pathogens. Strict germfree conditions delayed but did not completely prevent deposition; mice housed in these conditions had very low serum IgA levels and produced essentially monomeric IgA. Finally, comparing monoclonal IgA1 that had different variable regions and mesangial deposition patterns indicated that, independently of glycosylation and polymerization, deposition might also depend on IgA carrying specific variable domains. Together with IgA quantities and constant region post-translational modifications, repertoire changes during immune responses might, thus, modulate IgA propensity to deposition. These IgA features are not associated with circulating immune complexes and C3 deposition and are more pertinent to an initial IgA deposition step preceding overt clinical symptoms in patients.Agence Nationale de la Recherche; Ligue Nationale contre le Cancer; Conseil Régional du Limousin; European Community grants: (Fonds Européens de Développement Régional); Région Nord-Pas de Calais (France); Université des Sciences et Technologies de Lille 1.info:eu-repo/semantics/publishedVersio