Project description:Purpose: The goal of this study was to assess if TLR9 deficiency (TLR9-/-) or TLR9 incapacity to signal through MyD88 would differentially influence the gene programs of B cell subsets, in a B cell intrinsic manner. Methods : Mixed bone marrow chimeras of one-third each TLR9+/+ CD45.1/2, TLR9-/- CD45.1/1 and TLR9P915H/P915H CD45.2/2 were generated on the MRL/lpr background. From each recipient, three B cell subsets, FO, MZ and ABC were sorted with respect to the CD45 congenic markers at [x weeks] post chimerism. RNA was isolated using the RNeasy Plus Micro Kit (QIAGEN). Samples were sequenced using NovaSeq 6000 flowcell (Illumina, Inc, California, USA) with 100 bp paired-end reads (20 million reads per sample) and aligned to the mm10 genome using the STAR aligner. Results: ABCs showed the most transcriptional differences among TLR9 genotypes. TLR9P915H and TLR9WT ABC transcriptomes were much more similar to each other than to those of TLR9-/- mice, sharing 246 of 381 DEGs, even though TLR9P915H B cells could not signal via MyD88. These included a number of genes encoding for inhibitory or anti-inflammatory pathways, suggesting that TLR9 could induce a regulatory signal independently of MyD88.
Project description:We compared in vitro mTECs-high stimulated with TLR9 ligand CpG ODN (1826) or non stimulated from MyD88 -/- and MyD88 +/+ mice: Thymi were enzymaticaly digested, cells were MACS enriched for CD45- fraction, and FACS sorted using BD Influx sorter. mTECs-high were gated as EpCAM+CD11c-Ly51-MHCII+CD80+. Cell from MyD88 -/- and MyD88 +/+ mice were incubated in RPMI with or without CpG ODN (1826) for 24 hours. Total RNA was isolated using RNeasy Plus Micro Kit (Qiagen). 4 samples per condition were used.
Project description:CD4 T cell help is critical for both the generation and maintenance of germinal centers, and T follicular helper (TFH) cells are the CD4 T cell subset required for this process. SAP (SH2D1A) expression in CD4 T cells is essential for germinal center development. However, SAP-deficient mice have only a moderate defect in TFH differentiation as defined by common TFH surface markers. CXCR5+ TFH cells are found within the germinal center as well as along the boundary regions of T/B cell zones. Here we show that germinal center associated T cells (GC TFH) can be identified by their co-expression of CXCR5 and the GL7 epitope, allowing for phenotypic and functional analysis of TFH and GC TFH populations. Here we show GC TFH are a functionally discrete subset of further polarized TFH cells, with enhanced B cell help capacity and a specialized ability to produce IL-4 in a TH2-independent manner. Strikingly, SAP-deficient mice have an absence of the GC TFH subset and SAP- TFH are defective in IL-4 and IL-21 production. We further demonstrate that SLAM (Slamf1, CD150), a surface receptor that utilizes SAP signaling, is specifically required for IL-4 production by GC TFH. GC TFH cells require IL-4 and IL-21 production for optimal help to B cells. These data illustrate complexities of SAP-dependent SLAM family receptor signaling, revealing a prominent role for SLAM receptor ligation in IL-4 production by germinal center CD4 T cells but not in TFH and GC TFH differentiation. Analysis of in vivo polyclonal GC Tfh vs Tfh vs Non-Tfh eight days after LCMV viral infection. Analysis of in vivo follicular helper CD4 T cells (CXCR5high GL7low), versus germinal center follicular helper CD4 T cells (CXCR5hi GL7hi), versus non-follicular helper CD4 T cells (CXCR5low) eight days after viral infection.
Project description:Nuclear speckles are conserved, membrane-less organelles linked to various post-transcriptional processes. Here, we examined their roles in human cells by engineered, acute removal of SON and SRRM2, two conserved speckle core components characterized by intrinsically disordered regions (IDRs). Their removal results in a significant downregulation of GC-rich genes with short introns clustered within GC-rich isochores, caused by inefficient and chaotic splicing; in contrast, expression or splicing of genes outside these isochores remains unaffected. Comparative analysis across eukaryotes, from fungi to mammals, reveals that both GC-rich isochores and speckles are found exclusively in amniotes; moreover, the IDRs of SON have undergone notable expansion in the latter. Together, these findings suggest that the expansion of IDRs in vertebrates facilitated an increase in GC content by creating a condensate essential for splicing the by-products of this process: GC-rich, levelled exon-intron architectures.
