Project description:The B-cell receptor (BCR) enables individual B cells to identify diverse antigens, including bacterial and viral proteins. While advances in RNA-seq have enabled high throughput profiling of transcript expression in single cells, the unique task of assembling the full-length heavy and light chain sequences from single cell RNA-sequencing (scRNA-seq) in B cells has been largely unstudied. We developed a new software tool, BASIC, which allows investigators to use scRNA-seq for assembling BCR sequences at single cell level. To demonstrate the utility of our software, we subjected single B cells from a human donor to scRNA-seq, assembled the full-length heavy and the light chains, and experimentally confirmed these results by using single cell primer based nested PCRs and Sanger sequencing.
Project description:Purpose: B-1a cells have a distinct BCR repertoire compared with that of B-2 cells. To examine whether CIC loss affects the BCR repertoire in B-1a cells, we analyzed mRNA sequences of immunoglobulin heavy (Igh) and light (Igk and Igl) chain genes in B-1a cells from 12-week-old control and Cicf/f;Cd19-Cre mice. Methods: Peritoneal cavity B-1a cells (IgM+, CD19+, CD5+, CD43+) were sorted by a MoFlo-XDP (Beckman Coulter). Total RNA was extracted using TRIzol Reagent (GeneAll), according to the manufacturer’s instructions. Long Read iR-Profile Reagent System (iRepertoire) was used to generate NGS libraries covering BCR chains including Igh, Igk, and Igl. Briefly, nested inside and outside primers selectively amplified all V- and C- regions and incorporated communal adaptors. Following clean up, only target amplicons, which contain 5’ and 3’ communal adaptors, were exponentially amplified. Amplified libraries were multiplexed for sequencing on the Illumina Miseq platform. Sequence reads were de-multiplexed according to the barcode sequences. Results: Trimmed reads were mapped to germline V, D and J reference sequences downloaded from the IMGT database. IgH diversity and the usage of variable (V) segments in heavy (Ighv) chain and light (Igkv and Iglv) chain genes were comparable between control and Cic-null B-1a cells. Analysis of non-templated (N)-nucleotide addition at V(D)J junctions revealed that Cic-null B-1a cells have a higher proportion of zero to two N-nucleotides-containing-BCRs than control cells. Conclusions: Our study presents the first comparative BCR repertoire analysis of wild-type and Cic-null B-1a cells. We concluded that CIC deficiency does not dramatically alter the BCR repertoire in B-1a cells.
Project description:B cells are known to have different properties and BCR repertoires depending on the time of development. Our objective is to investigate the BCR repertoire of B cells across embryonic, neonatal, and adult stages, particularly in cells with a RAG2 expression history. We focus on sequencing and analyzing the immunoglobulin heavy chain (IGH) genes of these cells to understand their BCR diversity and specificity. Additionally, we explore the relationship between B-1a cells and bone marrow IgM+ plasmablasts/plasma cells, aiming to shed light on the development and function of B-1a cells in the immune system.
Project description:Motivation: The B-cell receptor (BCR) performs essential functions for the adaptive immune system including recognition of pathogen-derived antigens. The vast repertoire and adaptive variation of BCR sequences due to V(D)J recombination and somatic hypermutation (SHM) necessitates single-cell characterization of BCR sequences. Single-cell RNA sequencing (scRNA-seq) presents the opportunity for simultaneous capture of paired BCR heavy and light chains and the transcriptomic signature. Results: We developed VDJPuzzle, a novel bioinformatic tool that reconstructs productive, full-length B-cell receptor sequences of both heavy and light chains. VDJPuzzle successfully reconstructed BCRs from 98.3% (n=117) human and 96.5% (n=200) murine B cells. The reconstructed BCRs were successfully validated with single-cell Sanger sequencing. Availability: VDJPuzzle is available at https://bitbucket.org/kirbyvisp/vdjpuzzle2
Project description:This analysis focused on identifying factors that protect pre-B cells against DNA double strand break (DSB)-mediated DNA damage stress during pre-B cell differentiation. Differentiation of pre-B cells including immunoglobulin light chain gene recombination were performed by withdrawal of interleukin-7 (IL-7) from IL-7-dependent murine pre-B cells or by inhibition of the BCR-ABL1 kinase activity in BCR-ABL1-transformed pre-B cells. The BCR-ABL1 kinase inhibitor STI571 (Imatinib) was used for the inhibition of BCR-ABL1.
Project description:During B cell development the precursor B cell receptor (pre-BCR) checkpoint is thought to increase immunoglobulin k light chain (Igk) locus accessibility to the V(D)J recombinase. Accordingly, pre-B cells lacking the pre-BCR signaling molecules Btk or Slp65 showed reduced germline Vk transcription. To investigate whether pre-BCR signaling modulates Vk accessibility through enhancer-mediated Igk locus topology, we performed chromosome conformation capture and sequencing analyses. These revealed that already in pro-B cells the k enhancers robustly interact with the ~3.2 Mb Vk region and its flanking sequences. Analyses in wild-type, Btk and Slp65 single and double-deficient pre-B cells demonstrated that pre-BCR signaling reduces interactions of both enhancers with Igk locus flanking sequences and increases interactions of the 3’k enhancer with Vk genes. Remarkably, pre-BCR signaling does not significantly affect interactions between the intronic enhancer and Vk genes, which are already robust in pro-B cells. Both enhancers interact most frequently with highly used Vk genes, which are often marked by transcription factor E2a. We conclude that the k enhancers interact with the Vk region already in pro-B cells and that pre-BCR signaling induces accessibility through a functional redistribution of long-range chromatin interactions within the Vk region, whereby the two enhancers play distinct roles.
Project description:We report that B-1a cells develop in a surrogate light chain independent context. As a consequence, the precursor B-1a cell population avoids a pre-BCR positive selection stage. To confirm that the B-1a cells generated in this manner repersent a bonafide B-1a cell compartment, we did NGS on BCR rearrangements to assess the repertoire diversity. We find that as a whoile, B-1a cell repertoire that develop in Igll1 kncokout mice are similar compared to wild-type. This supports our findings that B-1a cells develop properly in the absence of surrogate light chain.
Project description:During B cell development the precursor B cell receptor (pre-BCR) checkpoint is thought to increase immunoglobulin k light chain (Igk) locus accessibility to the V(D)J recombinase. Accordingly, pre-B cells lacking the pre-BCR signaling molecules Btk or Slp65 showed reduced germline Vk transcription. To investigate whether pre-BCR signaling modulates Vk accessibility through enhancer-mediated Igk locus topology, we performed chromosome conformation capture and sequencing analyses. These revealed that already in pro-B cells the k enhancers robustly interact with the ~3.2 Mb Vk region and its flanking sequences. Analyses in wild-type, Btk and Slp65 single and double-deficient pre-B cells demonstrated that pre-BCR signaling reduces interactions of both enhancers with Igk locus flanking sequences and increases interactions of the 3â??k enhancer with Vk genes. Remarkably, pre-BCR signaling does not significantly affect interactions between the intronic enhancer and Vk genes, which are already robust in pro-B cells. Both enhancers interact most frequently with highly used Vk genes, which are often marked by transcription factor E2a. We conclude that the k enhancers interact with the Vk region already in pro-B cells and that pre-BCR signaling induces accessibility through a functional redistribution of long-range chromatin interactions within the Vk region, whereby the two enhancers play distinct roles. We performed genome-wide expression profiling of FACS-purified B220+CD19+ pre-B cell fractions from wild-type (WT), Btk and Slp65 single and double deficient VH81x transgenic Rag1-/- mice (n=4 of each genotype). In these experiments non-VH81x transgenic Rag1-/- pro-B cells served as controls (n=3).