Biology subjects

Chaudhuri, J.

Publications and source records attributed to Chaudhuri, J..

7 recordsLinked to original sources

bioRxiv2024

IL-21 Shapes the B Cell Response in a Context-Dependent Manner

The cytokine interleukin-21 (IL-21) is a pivotal T cell-derived signal crucial for germinal center (GC) responses, but the precise mechanisms by which IL-21 influences B cell function remain elusive. Here, we investigated the B cell-intrinsic role of IL-21 signaling by employing a novel IL-21 receptor (Il21r) conditional knock-out mouse model and ex vivo culture systems and uncovered a surprising duality of IL-21 signaling in B cells. While IL-21 stimulation of naive B cells led to Bim-dependent apoptosis, it promoted robust proliferation of pre-activated B cells, particularly class-switched IgG1+ B cells ex vivo. Consistent with this, B cell-specific deletion of Il21r led to a severe defect in IgG1 responses in vivo following immunization. Intriguingly, Il21r-deleted B cells are significantly impaired in their ability to transition from a pre-GC to a GC state following immunization. Although Il21r-deficiency did not affect the proportion of IgG1+ B cells among GC B cells, it greatly diminished the proportion of IgG1+ B cells among the plasmablast/plasma cell population. Collectively, our data suggest that IL-21 serves as a critical regulator of B cell fates, influencing B cell apoptosis and proliferation in a context-dependent manner.

immunology↗

bioRxiv2022

Methylglyoxal-derived hydroimidazolone, MG-H1, increases food intake by altering tyramine signaling via the GATA transcription factor ELT-3 in Caenorhabditis elegans

The Maillard reaction, a chemical reaction between amino acids and sugars, is exploited to produce flavorful food almost everywhere, from the baking industry to our everyday life. However, the Maillard reaction also takes place in all cells, from prokaryotes to eukaryotes, leading to the formation of Advanced Glycation End-products (AGEs). AGEs are a heterogeneous group of compounds resulting from the irreversible reaction between biomolecules and -dicarbonyls (-DCs), including methylglyoxal (MGO), an unavoidable byproduct of anaerobic glycolysis and lipid peroxidation. We previously demonstrated that Caenorhabditis elegans mutants lacking the glod-4 glyoxalase enzyme displayed enhanced accumulation of -DCs, reduced lifespan, increased neuronal damage, and touch hypersensitivity. Here, we demonstrate that glod-4 mutation increased food intake and identify that MGO-derived hydroimidazolone, MG-H1, is a mediator of the observed increase in food intake. RNA-seq analysis in glod-4 knockdown worms identified upregulation of several neurotransmitters and feeding genes. Suppressor screening of the overfeeding phenotype identified the tdc-1-tyramine-tyra-2/ser-2 signaling as an essential pathway mediating AGEs (MG-H1) induced feeding in glod-4 mutants. We also identified the elt-3 GATA transcription factor as an essential upstream factor for increased feeding upon accumulation of AGEs by partially regulating the expression of tdc-1 and tyra-2 genes. Further, the lack of either tdc-1 or tyra-2/ser-2 receptors suppresses the reduced lifespan and rescues neuronal damage observed in glod-4 mutants. Thus, in C. elegans, we identified an elt-3 regulated tyramine-dependent pathway mediating the toxic effects of MGO and associated AGEs. Understanding this signaling pathway is essential to modulate hedonistic overfeeding behavior observed in modern AGEs rich diets.

genetics↗

bioRxiv2022

ATM and MSH2 control blunt DNA end joining in immunoglobulin class switch recombination

Class switch recombination (CSR) produces secondary immunoglobulin isotypes and requires AID-dependent DNA deamination of intronic switch (S) regions within the immunoglobulin heavy chain (Igh) gene locus. Non-canonical repair of deaminated DNA by mismatch repair (MMR) or base excision repair (BER) creates DNA breaks that permit recombination between distal S regions. ATM-dependent phosphorylation of AID at serine-38 (pS38-AID) promotes its interaction with APE1, a BER protein, suggesting that ATM regulates CSR through BER. However, pS38-AID may also function in MMR during CSR, although the mechanism remains unknown. To examine whether ATM modulates BER- and/or MMR-dependent CSR, Atm-/- mice were bred to mice deficient for the MMR gene Msh2. Surprisingly, the predicted Mendelian frequencies of Atm-/-Msh2-/- adult mice were not obtained. To generate ATM and MSH2-deficient B cells, Atm was conditionally deleted on an Msh2-/- background using a floxed ATM allele [Atmf] and B cell-specific Cre recombinase expression (CD23-cre) to produce a deleted ATM allele (AtmD). As compared to AtmD/Dand Msh2-/- mice and B cells, AtmD/DMsh2-/- mice and B cells display a reduced CSR phenotype. Interestingly, S-S{gamma}1 junctions from AtmD/DMsh2-/-B cells that were induced to switch to IgG1 in vitro showed a significant loss of blunt end joins and an increase in insertions as compared to wildtype, AtmD/D, or Msh2-/- B cells. This data indicates that the absence of both ATM and MSH2 blocks non-homologous end joining (NHEJ), leading to inefficient CSR. We propose a model whereby ATM and MSH2 function cooperatively to regulate end-joining during CSR through pS38-AID. SummaryLoss of the DNA repair genes Atm and Msh2 produces a novel synthetic lethality in mice. B cell specific deletion of Atm on an Msh2-/- background reduces Ig CSR and inhibits NHEJ.

immunology↗

bioRxiv2022

The Structure-Selective Endonucleases GEN1 and MUS81 are Functionally Complementary in Safeguarding the Genome of Proliferating B Lymphocytes

During the development of humoral immunity, activated B lymphocytes undergo vigorous proliferative, transcriptional, metabolic, and DNA remodeling activities; hence, their genomes are constantly exposed to an onslaught of genotoxic agents and processes. Recombination-dependent DNA transactions that preserve the integrity of the genome and of the DNA replication process generates Holliday junctions that must be eliminated for the accurate segregation of sister chromatids and faithful propagation of genomic material. To investigate the role of two Holliday junction resolvases, GEN1 and MUS81, in B cell biology, we established B-cell conditional knockout mouse models and found that targeted deletion of GEN1 and MUS81 in early B cell precursors halts their development and maturation while selective loss of the resolvases in mature B cells inhibits the generation of robust germinal centers. Upon activation, these double-null mature B lymphocytes fail to proliferate and survive while exhibiting transcriptional signatures of p53 signaling, apoptosis, and type I interferon response. Metaphase spreads of these resolvase-deficient cells showed severe and diverse chromosomal abnormalities, including a preponderance of chromosome breaks, consistent with a defect in resolving DNA recombination intermediates. These observations underscore the essential roles of GEN1 and MUS81 in safeguarding the genome to ensure the proper development and maintenance of B lymphocytes.

immunology↗

bioRxiv2021

A study of Mutation in ATP7B gene and its correlation with clinical phenotype and radiological features in Wilson Disease patients

IntroductionWilson Disease (WD) is an autosomal recessive disease caused by mutations in the ATP7B gene. Clinical manifestations of WD are variable. Identification of prevalent mutations in a given population is necessary to provide mutation-based molecular diagnosis. Previous studies have detected common mutations in this part of the world and our study aimed to correlate genotype with clinical and radiological features. MethodsA descriptive cross-sectional observational study was conducted over a period of two years in a tertiary care hospital and neurology referral unit of Kolkata, India. All WD patients within the study period and meeting the inclusion criteria were included. Demographic data collection, clinical examination and relevant laboratory investigations were done. Magnetic resonance imaging of brain and cognitive assessment by Mini Mental Score Exam (MMSE) were also performed. Blood was collected for genetic analyses. PCR-Sanger sequencing of exons 2,4,6,8,10,14,16,18 of ATP7B gene was done based on previous reports of mutation hotspots of ATP7B gene for WD in Eastern India. Genotype phenotype correlation was attempted using two supervised machine learning methods, viz. logistic regression with an elastic-net penalty and the random forest. ResultsOf 52 WD patients were included in the study, 57.7% were males. The mean age at diagnosis was 13.96 years. Majority (61.8%) of the patients had dystonia on presentation, followed by dysarthria (41.2%), tremor (17.6%) and ataxia (11.8%). The mean MMSE and Frontal Assessment Battery score were 23.74 and 10.63 respectively and both were lower than the normal baseline values.Out of the total cohort of 52 patients,15(28.8%) harbored previously reported common mutations from this part of the country. Of the 15, 12 had the same mutation of c.813C>A(p.cys271Ter).The presence of common mutationswas associated with several distinct clinical phenotypes in the mathematical models but larger sample sizes are needed to corroborate the correlation. ConclusionsWD patients in eastern India have significant genotypic and phenotypic diversity. Further studies with larger samples and screening of remaining exons are warranted.

neuroscience↗

bioRxiv2018

Sensory neurons control heritable adaptation to stress through germline reprogramming

Maternal neuronal signaling has been reported to program adaptive changes in offspring physiology in diverse organisms [1, 2]. However, the mechanisms for the inheritance of adaptive maternal effects through the germline are largely unknown. In the nematode Auanema freiburgensis, stress-resistance and sex of the offspring depend on environmental cues experienced by the mother. Maternal sensing of high population densities results in the production of stress-resistant larvae (dauers) that develop into hermaphrodites. Ablation of the maternal ASH chemosensory neurons results only in non-dauer offspring that develop into males or females. High population densities correlate with changes in the methylation status of H3K4 and H3K9 in the maternal germline. Inhibition of JMJD histone demethylases prevents mothers from producing dauers and hermaphrodite offspring in high-density conditions. Our results demonstrate a case of soma-to-germline transmission of environmental information that influences the phenotype of the following generation through changes in histone modifications of the maternal germline.\n\nHighlightsO_LIHigh population density leads to the production of hermaphrodite offspring.\nC_LIO_LIThe ASH neuron in the hermaphrodite mother senses population density.\nC_LIO_LIHistone modifications in the maternal germline correlate with the sex of offspring.\nC_LIO_LIInhibition of histone demethylases results in female offspring in all conditions.\nC_LI

developmental biology↗

bioRxiv2018

Outflanking Immunodominance to Target Subdominant Broadly Neutralizing Epitopes

A major obstacle to vaccination to antigenically variable viruses is skewing of antibody responses to immunodominant epitopes. For influenza virus hemagglutinin (HA), the immunodominance of the variable head impairs responses to the highly conserved stem. Here, we show that head immunodominance depends on the physical attachment of head to stem. Stem immunogenicity is enhanced by immunizing with stem only-constructs or by increasing local HA concentration in the draining lymph node. Surprisingly, co-immunization of HA and stem alters stem-antibody class switching. Our findings delineate strategies for overcoming immunodominance with important implications for human vaccination.

immunology↗