Switch Recombination Research Articles

The hidden architects of the genome: a comprehensive review of R-loops.

Three-stranded DNA: RNA hybrids known as R-loops form when the non-template DNA strand is displaced and the mRNA transcript anneals to its template strand. Although R-loop formation controls DNA damage response, mitochondrial and genomic transcription, and physiological R-loop formation, imbalanced formation of R-loop can jeopardize a cell's genomic integrity. Transcription regulation and immunoglobulin class switch recombination are two further specialized functions of genomic R-loops. R-loop formation has a dual role in the development of cancer and disturbed R-loop homeostasis as observed in several malignancies. R-loops transcribe at the telomeric and pericentromeric regions, develop in the space between long non-coding RNAs and telomeric repeats, and shield telomeres. In bacteria and archaea, R-loop development is a natural defence mechanism against viruses which also causes DNA degradation. Their emergence in the mammalian genome is controlled, suggesting that they were formed as an inevitable byproduct of RNA transcription but also co-opted for regulatory functions. R-loops may be engaged in cell physiology by regulating gene expression. R-loop biology is probably going to remain a fascinating field of study for a very long time as it offers many avenues for R-loop research.

Suppression of Class Switch Recombination to IgA by RASA2 and RASA3 through Inhibition of TGF-β Signaling.

Abs play a pivotal role in adaptive immunity by binding to pathogens and initiating immune responses against infections. Processes such as somatic hypermutation and class switch recombination (CSR) enhance Ab affinity and effector functions. We previously carried out a CRISPR/Cas9 screen in the CH12F3-2 (CH12) lymphoma B cell line to identify novel factors involved in CSR. The screen showed that guide RNAs targeting both Rasa2 and Rasa3 genes were decreased in IgA-negative CH12 B cells, implying that these genes might suppress CSR. Indeed, CSR was increased when either Rasa2 or Rasa3 were knocked out in CH12 cells. Compared to controls, Rasa2-/- and Rasa3-/- CH12 cells had increased expression of activation-induced cytidine deaminase (AID) and Iα transcripts, providing an explanation for the increased CSR. The increased CSR, AID, and Iα expression in Rasa2-/- or Rasa3-/- CH12F3-2 is mediated through TGF-β stimulation. Indeed, we found that deletion of RASA2 or RASA3 promotes a shift from noncanonical to canonical TGF-β signaling through SMAD3. These results show that RASA2 and RASA3 are both novel regulators of TGF-β signaling in B cells, a pathway known to be essential for CSR to IgA.

Core enhancers of the 3'RR optimize IgH nuclear position and loop conformation for successful oriented class switch recombination.

In B lymphocytes, class switch recombination (CSR) is an essential process that adapts immunoglobulin (Ig) subtypes to antigenresponse. Taking place within the Ig heavy chain (IgH) locus, CSR needs controlled transcription of targeted regions governed by the IgH 3'regulatory region (3'RR). This super-enhancer is composed of four core enhancers surrounded by inverted repeated sequences, forming a quasi-palindrome. In addition to transcription, nuclear organization appears to be an important level in CSR regulation. While it is now established that chromatin loop extrusion takes place within IgH locus to facilitate CSR by bringing the donor and acceptor switch regions closer together, the underlying mechanism that triggers CSR loop formation remains partially understood. Here, by combining DNA 3Dfluorescence in situhybridizationwith various high-throughput approaches, we deciphered critical functions for the 3'RR core enhancer element in nuclear addressing, accessibility and chromatin looping of the IgH locus. We conclude thatthe 3'RR core enhancers are necessary and sufficient to pre-organize the position and conformation of IgH loci in resting B-cell nuclei to enable the deletional recombination events required for productive successful CSR in activated B-cell nuclei.

Intrinsic functional defects in B cells of patients with NFKB2 mutations.

Mutations in the human nuclear factor-κB2 gene (NFKB2) are associated with common variable immunodeficiency (CVID) or combined immunodeficiency diseases (CID), characterized by B-cell lymphopenia, hypogammaglobulinemia, and T cell dysfunction. This study investigated whether B cells with NFKB2 mutations exhibit intrinsic impairments in activation, class-switch recombination, and differentiation. We analyzed five patients from four unrelated families with CVID, each carrying a heterozygous NFKB2 mutation: P1 (C.2595_2614del, p.A867Gfs*12), P2 (C.2597G>A, p.S866N), P3 (C.2540dupT, p.R848Efs*38), and P4 and P5 (C.2570_2571insCAGCACA, p.A860Qfs*28). The patients with frameshift mutations (P1, P3, P4, and P5) exhibited truncated proteins detectable in their peripheral blood mononuclear cells, while P2 had a missense mutation. All identified mutations disrupted the processing of p100 into the active p52 form, resulting in NF-κB2 loss-of-function and IκBδ gain-of-function. Clinically, P1, P2, and P3 exhibited B-cell lymphopenia, and all five patients presented with hypogammaglobulinemia. Notably, P2 exhibited a markedly low B-cell count, associated with increased proportions of memory B and IgD-CD27- double negative B cells. In vitro experiments with naïve B cells from P1 and P4 demonstrated decreased survival, impaired activation, and reduced differentiation into CD27+IgD- cells and plasmablasts, while class switch recombination was unaffected. These findings reveal novel B cell-intrinsic functional defects in patients with NFKB2 mutations.

Transcription elongation factor ELOF1 is required for efficient somatic hypermutation and class switch recombination.

Somatic hypermutation (SHM) and class switch recombination (CSR) diversify immunoglobulin (Ig) genes and are initiated by the activation induced deaminase (AID), a single-stranded DNA cytidine deaminase that is thought to engage its substrate in the context of RNA polymerase II (RNAPII) transcription. Through a loss of function genetic screen, we identified numerous potential factors involved in SHM including ELOF1, a component of the RNAPII elongation complex that has been shown to function in DNA repair and transcription elongation. Loss of ELOF1 strongly compromises SHM, CSR, and AID targeting and alters RNAPII transcription by reducing RNAPII pausing downstream of transcription start sites and levels of serine 5 but not serine 2 phosphorylated RNAPII throughout transcribed genes. ELOF1 must bind to RNAPII to be a proximity partner for AID and to function in SHM and CSR. We propose that ELOF1 helps create the appropriate stalled RNAPII substrate on which AID acts.

Negative regulation of activation-induced cytidine deaminase gene transcription in developing B cells by a PU.1-interacting intronic region

Activation-induced cytidine deaminase (AID, encoded by Aicda) plays a key role in somatic hypermutation and class switch recombination in germinal center B cells. However, off-target effects of AID are implicated in human leukemia and lymphoma. A mouse model of precursor B cell acute lymphoblastic leukemia driven by deletion of the related transcription factors PU.1 and Spi-B revealed C->T transition mutations compatible with being induced by AID. Therefore, we hypothesized that PU.1 negatively regulates Aicda during B cell development. Aicda mRNA transcript levels were increased in leukemia cells and bone marrow pre-B cells lacking PU.1 and/or Spi-B, relative to wild type cells. Using chromatin immunoprecipitation, PU.1 was found to interact with a negative regulatory region (R2–1) within the first intron of Aicda. CRISPR-Cas9-induced mutagenesis of R2–1 in cultured pre-B cells resulted in upregulation of Aicda in response to lipopolysaccharide stimulation. Mutation of the PU.1 interaction site and neighboring sequences resulted in reduced repressive ability of R2–1 in transient transfection analysis followed by luciferase assays. These results show that a PU.1-interacting intronic region negatively regulates Aicda transcription in developing B cells.

BCR ligation selectively inhibits IgE class switch recombination.

Mechanisms that restrict class switch recombination (CSR) to IgE limit the subsequent production of IgE antibodies and therefore the development of allergic disease. Mice with impaired B cell receptor (BCR) signaling have significantly increased IgE responses, consistent with a role for BCR signaling in IgE regulation. While prior work focused on BCR signaling in IgE-expressing cells to explain these findings, it has been reported that BCR signaling can reduce CSR. Therefore, we investigated the possibility that IgE CSR might be particularly sensitive to inhibition by BCR signaling in unswitched B cells. We found that immunization of mice with high-affinity antigen resulted in reduced representation of IgE-expressing cells among germinal center B cells and plasma cells relative to a low-affinity antigen. Mechanistic experiments with cultured mouse B cells demonstrated that BCR ligands selectively inhibited IgE CSR in a dose-, affinity-, and avidity-dependent manner. Signaling via Syk was required for the inhibition of IgE CSR following BCR stimulation, whereas inhibition of the PI3K subunit p110δ increased IgE CSR independently of BCR ligation. The inhibition of IgE CSR by BCR ligands synergized with IL-21 or TGFβ1. BCR ligation also inhibited CSR to IgE in human tonsillar B cells, and this inhibition was also synergistic with IL-21. These findings establish that IgE CSR is uniquely susceptible to inhibition by BCR signaling in mouse and human B cells, with important implications for the regulation and pathogenesis of allergic disease.

Imatinib mesylate reduces c-MYC expression in double-hit lymphoma cells by suppressing inducible cytidine deaminase

BackgroundDouble-hit lymphoma (DHL) with c-MYC gene translocation is highly aggressive and has a poor prognosis. In DHL cells, activation-induced cytidine deaminase (AID) promotes antibody class switch recombination (CSR), ultimately leading to c-MYC gene translocation caused by Myc/IgH DNA double-strand breaks. However, currently there is still no method to suppress the expression of AID.MethodsIn this study, we compared the clinical significance of AID expression in DHL, Additionally, two human double-hit lymphoma cell lines were used to analyze the effect of imatinib mesylate on c-MYC in vitro, and the therapeutic effect was also evaluated in xenograft mouse models.ResultsImatinib mesylate downregulated the AID and c-MYC proteins in patients with chronic myelogenous leukemia associated with DHL. In addition, imatinib mesylate reduced AID and c-MYC expression in SU-DHL-4 and OCI-Ly18DHL cells. Imatinib mesylate exerted significant inhibitory effects on the proliferation and metastasis of SU-DHL-4 and OCI-Ly18 cells. Finally, imatinib mesylate reduced not only tumor burden in DHL mouse models, but also AID and c-MYC expression in vivo.ConclusionThese findings reveal that imatinib mesylate effectively reduces the carcinogenic function of c-MYC in DHL, providing novel strategies for developing therapies targeting c-MYC-driven DHL.Graphical abstract

Immunogenetic Landscape in Pediatric Common Variable Immunodeficiency.

Common variable immunodeficiency (CVID) is the most common symptomatic antibody deficiency, characterized by heterogeneous genetic, immunological, and clinical phenotypes. It is no longer conceived as a sole disease but as an umbrella diagnosis comprising a spectrum of clinical conditions, with defects in antibody biosynthesis as their common denominator and complex pathways determining B and T cell developmental impairments due to genetic defects of many receptors and ligands, activating and co-stimulatory molecules, and intracellular signaling molecules. Consequently, these genetic variants may affect crucial immunological processes of antigen presentation, antibody class switch recombination, antibody affinity maturation, and somatic hypermutation. While infections are the most common features of pediatric CVID, variants in genes linked to antibody production defects play a role in pathomechanisms of immune dysregulation with autoimmunity, allergy, and lymphoproliferation reflecting the diversity of the immunogenetic underpinnings of CVID. Herein, we have reviewed the aspects of genetics in CVID, including the monogenic, digenic, and polygenic models of inheritance exemplified by a spectrum of genes relevant to CVID pathophysiology. We have also briefly discussed the epigenetic mechanisms associated with micro RNA, DNA methylation, chromatin reorganization, and histone protein modification processes as background for CVID development.

FAM72A degrades UNG2 through the GID/CTLH complex to promote mutagenic repair during antibody maturation

A diverse antibody repertoire is essential for humoral immunity. Antibody diversification requires the introduction of deoxyuridine (dU) mutations within immunoglobulin genes to initiate somatic hypermutation (SHM) and class switch recombination (CSR). dUs are normally recognized and excised by the base excision repair (BER) protein uracil-DNA glycosylase 2 (UNG2). However, FAM72A downregulates UNG2 permitting dUs to persist and trigger SHM and CSR. How FAM72A promotes UNG2 degradation is unknown. Here, we show that FAM72A recruits a C-terminal to LisH (CTLH) E3 ligase complex to target UNG2 for proteasomal degradation. Deficiency in CTLH complex components result in elevated UNG2 and reduced SHM and CSR. Cryo-EM structural analysis reveals FAM72A directly binds to MKLN1 within the CTLH complex to recruit and ubiquitinate UNG2. Our study further suggests that FAM72A hijacks the CTLH complex to promote mutagenesis in cancer. These findings show that FAM72A is an E3 ligase substrate adaptor critical for humoral immunity and cancer development.

Isotype-aware inference of B cell clonal lineage trees from single-cell sequencing data

Single-cell RNA sequencing (scRNA-seq) enables comprehensive characterization of the micro-evolutionary processes of B cells during an adaptive immune response, capturing features of somatic hypermutation (SHM) and class switch recombination (CSR). Existing phylogenetic approaches for reconstructing B cell evolution have primarily focused on the SHM process alone. Here, we present tree inference of B cell clonal lineages (TRIBAL), an algorithm designed to optimally reconstruct the evolutionary history of B cell clonal lineages undergoing both SHM and CSR from scRNA-seq data. Through simulations, we demonstrate that TRIBAL produces more comprehensive and accurate B cell lineage trees compared to existing methods. Using real-world datasets, TRIBAL successfully recapitulates expected biological trends in a model affinity maturation system while reconstructing evolutionary histories with more parsimonious class switching than state-of-the-art methods. Thus, TRIBAL significantly improves B cell lineage tracing, useful for modeling vaccine responses, disease progression, and the identification of therapeutic antibodies.

Phosphoryl oligosaccharide alleviates food allergy by suppressing IgE class switch recombination through LCN2 pathway

Specific algal polysaccharides exhibit significant anti-allergic activity. B cell class switch recombination (CSR) is a crucial step in food allergies, however, the role of polysaccharides in regulating CSR remains unclear. To investigate the regulation of B cell CSR by algal polysaccharides, an in vitro IgE-type CSR cell model was used to screen for active algal polysaccharides, and four active polysaccharides were identified. In a food allergy mouse model, Undaria pinnatifida polysaccharides (UPP) and phosphoryl oligosaccharides (POS) suppressed allergic responses and reduced the proliferation of IgE+ B cells. Transcriptome sequencing of B cells identified LCN2 as a potential target of POS, and inhibition of LCN2 blocked the activity of POS on CSR. These findings demonstrated the efficacy of POS in regulating B cell CSR and alleviating allergic responses and revealed the underlying mechanisms. This work provided data and theoretical support for the development of polysaccharide-based functional foods for individuals with allergies.

B-Cell Epigenetic Modulation of IgA Response by 5-Azacytidine and IgA Nephropathy.

IgA nephropathy is an important global cause of kidney failure. Dysregulation of IgA production is thought to play a key role in IgA nephropathy pathogenesis, however, little is known about the epigenetic mechanisms such as RNA 5- methylcytosine (5mC) modification in regulating IgA synthesis. To decipher the role of RNA 5mC in regulation of IgA class switch, the miR-23b-/- and LCWE induced Kawasaki disease mice were treated with 5-azacytidine. Trdmt1-/- and double Trdmt1-/-/ miR-23b-/- mice, Aid-/- mice or Aid-/-/ miR-23b-/- mice were also employed. We showed that miR-23b down regulated expression of Transfer RNA Aspartic Acid Methyltransferase 1 (Trdmt1) and consequently reduced 5-methylcytosine (m5C) RNA modification and IgA synthesis in B cells. Inhibition of m5C RNA modification normalised serum IgA levels and ameliorated progression of the IgA nephropathy-like kidney disease in miR-23b-/- and Kawasaki disease mice while mesangial IgA and C3 deposition failed to develop in Trdmt1-/-miR-23b-/- mice. By contrast, increased m5C RNA modification resulted in an exaggerated IgA nephropathy phenotype. miR-23b regulation of serum IgA levels and the development of an IgA nephropathy-like kidney disease in miR-23b-/- and Kawasaki disease mice is likely mediated through TRDMT1 driven 5-methylcytosine RNA modification in B cells, resulting in impaired activation-induced cytidine deaminase activity and IgA class switch recombination. This study revealed TRDMT1 induced RNA 5mC methylation regulate IgA class switch and inhibition of RNA 5mC by 5-Azacytidine could ameliorate progression of IgA nephropathy.

Moderate Aerobic Exercise Induces Homeostatic IgA Generation in Senile Mice.

A T-cell-independent (TI) pathway activated by microbiota results in the generation of low-affinity homeostatic IgA with a critical role in intestinal homeostasis. Moderate aerobic exercise (MAE) provides a beneficial impact on intestinal immunity, but the action of MAE on TI-IgA generation under senescence conditions is unknown. This study aimed to determine the effects of long-term MAE on TI-IgA production in young (3 month old) BALB/c mice exercised until adulthood (6 months) or aging (24 months). Lamina propria (LP) from the small intestine was obtained to determine B cell and plasma cell sub-populations by flow cytometry and molecular factors related to class switch recombination [Thymic Stromal Lymphopoietin (TSLP), A Proliferation-Inducing Ligand (APRIL), B Cell Activating Factor (BAFF), inducible nitric oxide synthase (iNOS), and retinal dehydrogenase (RDH)] and the synthesis of IgA [α-chain, interleukin (IL)-6, IL-21, and Growth Factor-β (TGF-β)]; and epithelial cells evaluated IgA transitosis [polymeric immunoglobulin receptor (pIgR), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), IL-4] by the RT-qPCR technique. The results were compared with data obtained from sedentary age-matched mice. Statistical analysis was computed with ANOVA, and p < 0.05 was considered to be a statistically significant difference. Under senescence conditions, MAE promoted the B cell and IgA+ B cells and APRIL, which may improve the intestinal response and ameliorate the inflammatory environment associated presumably with the downmodulation of pro-inflammatory mediators involved in the upmodulation of pIgR expression. Data suggested that MAE improved IgA and downmodulate the cytokine pro-inflammatory expression favoring homeostatic conditions in aging.

RNA 2'-O-methylation promotes persistent R-loop formation and AID-mediated IgH class switch recombination

BackgroundRNA–DNA hybrids or R-loops are associated with deleterious genomic instability and protective immunoglobulin class switch recombination (CSR). However, the underlying phenomenon regulating the two contrasting functions of R-loops is unknown. Notably, the underlying mechanism that protects R-loops from classic RNase H-mediated digestion thereby promoting persistence of CSR-associated R-loops during CSR remains elusive.ResultsHere, we report that during CSR, R-loops formed at the immunoglobulin heavy (IgH) chain are modified by ribose 2′-O-methylation (2′-OMe). Moreover, we find that 2′-O-methyltransferase fibrillarin (FBL) interacts with activation-induced cytidine deaminase (AID) associated snoRNA aSNORD1C to facilitate the 2′-OMe. Moreover, deleting AID C-terminal tail impairs its association with aSNORD1C and FBL. Disrupting FBL, AID or aSNORD1C expression severely impairs 2′-OMe, R-loop stability and CSR. Surprisingly, FBL, AID’s interaction partner and aSNORD1C promoted AID targeting to the IgH locus.ConclusionTaken together, our results suggest that 2′-OMe stabilizes IgH-associated R-loops to enable productive CSR. These results would shed light on AID-mediated CSR and explain the mechanism of R-loop-associated genomic instability.

TGF-β1 impairs IgA class switch recombination and production in porcine Peyer's patches B cells.

Secretory IgA is crucial for preventing the invasion of entero-pathogens via intestinal mucosa. While it is well-established that Transforming growth factor β1 (TGF-β1) regulates IgA production in human and mouse B cells, our previous investigation revealed different functions of TGF-β1 in IgA generation in pigs compared with humans and mice, with the underlying mechanism remaining elusive. In this study, IgM+ B cells from porcine Peyer's patches (PPs) were isolated and stimulated with recombinant porcine TGF-β1 to evaluate the effect of TGF-β1 on pigs. The results showed that antibody production from B cells of PPs was impaired by TGF-β1 ex vivo. Furthermore, TGF-β1 treatment led to a decrease in the expression of germ-line transcript αand postswitch transcript α. Moreover, we observed that TGF-β1 predominantly inhibited the phosphorylation of p38-mitogen-activated protein kinases (MAPK), confirming the involvement of the p38-MAPK pathway in porcine IgA generation and IgA class switch recombination. The application of p38-MAPK inhibitor resulted in decreased B-cell differentiation levels. Collectively, this study demonstrates that exogenous TGF-β1 restrains the production and class switch recombination of IgA antibodies by inhibiting p38-MAPK signaling in porcine PPs B cells, which may constitute a component of TGF-β1-mediated inhibition of B-cell activation.

Dupilumab treatment decreases MBC2s, correlating with reduced IgE levels in pediatric atopic dermatitis

BackgroundA preference for type 2 immunity plays a central role in the pathogenesis of atopic dermatitis (AD). Dupilumab, a monoclonal antibody targeting the IL-4α receptor subunit, inhibits IL-4 and IL-13 signaling. These cytokines contribute significantly to IgE class switch recombination in B-cells, critical in atopic diseases. Recent studies indicate IgG+CD23hiIL-4RA+ memory B-cells (MBC2) as IgE-producing B-cell precursors, linked to total IgE serum levels in atopic patients. Total IgE serum levels decreased during dupilumab treatment in previous studies. ObjectiveTo assess the effects of dupilumab treatment in comparison to alternative therapies on the frequency of MBC2 and the correlation to total IgE levels in pediatric patients with AD. MethodsPediatric patients with AD, participating in an ongoing trial, underwent randomization into three treatment groups: dupilumab (n=12), cyclosporine (n=12), or topical treatment (n=12). Plasma and Peripheral Blood Mononuclear Cells (PBMCs) were collected at baseline (T0) and after 6 months (T6). Flow cytometry was employed for PBMC phenotyping, ELISA was utilized to assess total IgE levels in plasma. For detailed Methods, please see the Methods section in this article's Online Repository at www.jacionline.org ResultsOur findings revealed a significant reduction in MBC2 frequency and total IgE levels among patients treated with dupilumab. Additionally, a significant correlation was observed between MBC2s and total IgE levels ConclusionSystemic blocking of the IL-4RA subunit leads to a decrease in circulating MBC2 cells and total IgE in pediatric AD patients. Our findings unveil a novel mechanism through which dupilumab exerts its influence on the atopic signature.

The multifaceted functions of DNA-PKcs: implications for the therapy of human diseases.

The DNA-dependent protein kinase(DNA-PK), catalytic subunit, also known as DNA-PKcs, is complexed with the heterodimer Ku70/Ku80 to form DNA-PK holoenzyme, which is well recognized as initiator in the nonhomologous end joining (NHEJ) repair after double strand break (DSB). During NHEJ, DNA-PKcs is essential for both DNA end processing and end joining. Besides its classical function in DSB repair, DNA-PKcs also shows multifaceted functions in various biological activities such as class switch recombination (CSR) and variable (V) diversity (D) joining (J) recombination in B/T lymphocytes development, innate immunity through cGAS-STING pathway, transcription, alternative splicing, and so on, which are dependent on its function in NHEJ or not. Moreover, DNA-PKcs deficiency has been proven to be related with human diseases such as neurological pathogenesis, cancer, immunological disorder, and so on through different mechanisms. Therefore, it is imperative to summarize the latest findings about DNA-PKcs and diseases for better targeting DNA-PKcs, which have shown efficacy in cancer treatment in preclinical models. Here, we discuss the multifaceted roles of DNA-PKcs in human diseases, meanwhile, we discuss the progresses of DNA-PKcs inhibitors and their potential in clinical trials. The most updated review about DNA-PKcs will hopefully provide insights and ideas to understand DNA-PKcs associated diseases.

Malic enzyme 1 knockout has no deleterious phenotype and is favored in the male germline under standard laboratory conditions.

Malic Enzyme 1 (ME1) plays an integral role in fatty acid synthesis and cellular energetics through its production of NADPH and pyruvate. As such, it has been identified as a gene of interest in obesity, type 2 diabetes, and an array of epithelial cancers, with most work being performed in vitro. The current standard model for ME1 loss in vivo is the spontaneous Mod-1 null allele, which produces a canonically inactive form of ME1. Herein, we describe two new genetically engineered mouse models exhibiting ME1 loss at dynamic timepoints. Using murine embryonic stem cells and Flp/FRT and Cre/loxP class switch recombination, we established a germline Me1 knockout model (Me1 KO) and an inducible conditional knockout model (Me1 cKO), activated upon tamoxifen treatment in adulthood. Collectively, neither the Me1 KO nor Me1 cKO models exhibited deleterious phenotype under standard laboratory conditions. Knockout of ME1 was validated by immunohistochemistry and genotype confirmed by PCR. Transmission patterns favor Me1 loss in Me1 KO mice when maternally transmitted to male progeny. Hematological examination of these models through complete blood count and serum chemistry panels revealed no discrepancy with their wild-type counterparts. Orthotopic pancreatic tumors in Me1 cKO mice grow similarly to Me1 expressing mice. Similarly, no behavioral phenotype was observed in Me1 cKO mice when aged for 52 weeks. Histological analysis of several tissues revealed no pathological phenotype. These models provide a more modern approach to ME1 knockout in vivo while opening the door for further study into the role of ME1 loss under more biologically relevant, stressful conditions.

Toll-Like Receptor Activation and B Cell Maturation Via MyD88-Dependent Pathway Under Hyperglycemia Condition

hyperglycemia causes a degenerative syndrome that involves an inflammatory process with an increase in certain proinflammatory cytokines and chemokines which in the process will activate B cells to produce immunoglobulins through several mechanisms. One of the interesting mechanisms is the mechanism via the MyD88 pathway. Objectives: to explore the role of MyD88 adapter protein in Toll-like receptor activation and B cell maturation under hyperglycemia conditions. Methods: a literature review was done to answer the study objectives. Results: Class switching process under hyperglycemia conditions involves activation of NFkB through the inflammatory MyD88-dependent pathway to trigger the expression of TLR and B cell maturation and proliferation as well as antibody production. The MyD88 adapter protein is a protein formed by stimulation of pro-inflammatory cytokines IL-6 and plays a role in the continuation of signals from the TLR and IL-1 pathways. Mature B cell stimulation induces 2 genetic changes in the Ig gene locus, called somatic hypermutation (SHM) and class switch recombination (CSR) to produce antibodies. Changes in immunoglobulin genes occur related to changes in certain DNA segments at the locus of genes where CSR occurs, this gene change requires the role of AID (activated-induced cytidine deaminase) in DNA cleavage. AID in mature B cells is activated by proinflammatory cytokines via induction of NfKB activation via the inflammatory MyD88-dependent pathway. Conclusion: Toll-like receptor activation plays a crucial role in B cell maturation activated by pro-inflammatory cytokine via MyD88 dependent-NFkB activation.