PILRα negatively regulates mouse inflammatory arthritis.

Paired Ig-like type 2 receptor (PILR)α inhibitory receptor and its counterpart PILRß activating receptor are coexpressed on myeloid cells. In this article, we report that PILRα, but not PILRß, is elevated in human rheumatoid arthritis synovial tissue and correlates with inflammatory cell infiltration. Pilrα(-/-) mice produce more pathogenic cytokines during inflammation and are prone to enhanced autoimmune arthritis. Correspondingly, engaging PILRα with anti-PILRα mAb ameliorates inflammation in mouse arthritis models and suppresses the production of proinflammatory cytokines. Our studies suggest that PILRα mediates an important inhibitory pathway that can dampen inflammatory responses.

Polyclonal hyper-IgE mouse model reveals mechanistic insights into antibody class switch recombination.

Preceding antibody constant regions are switch (S) regions varying in length and repeat density that are targets of activation-induced cytidine deaminase. We asked how participating S regions influence each other to orchestrate rearrangements at the IgH locus by engineering mice in which the weakest S region, Sε, is replaced with prominent recombination hotspot Sµ. These mice produce copious polyclonal IgE upon challenge, providing a platform to study IgE biology and therapeutic interventions. The insertion enhances ε germ-line transcript levels, shows a preference for direct vs. sequential switching, and reduces intraswitch recombination events at native Sµ. These results suggest that the sufficiency of Sµ to mediate IgH rearrangements may be influenced by context-dependent cues.

Evolutionarily conserved paired immunoglobulin-like receptor α (PILRα) domain mediates its interaction with diverse sialylated ligands.

Paired immunoglobulin-like receptor (PILR) α is an inhibitory receptor that recognizes several ligands, including mouse CD99, PILR-associating neural protein, and Herpes simplex virus-1 glycoprotein B. The physiological function(s) of interactions between PILRα and its cellular ligands are not well understood, as are the molecular determinants of PILRα/ligand interactions. To address these uncertainties, we sought to identify additional PILRα ligands and further define the molecular basis for PILRα/ligand interactions. Here, we identify two novel PILRα binding partners, neuronal differentiation and proliferation factor-1 (NPDC1), and collectin-12 (COLEC12). We find that sialylated O-glycans on these novel PILRα ligands, and on known PILRα ligands, are compulsory for PILRα binding. Sialylation-dependent ligand recognition is also a property of SIGLEC1, a member of the sialic acid-binding Ig-like lectins. SIGLEC1 Ig domain shares ∼22% sequence identity with PILRα, an identity that includes a conserved arginine localized to position 97 in mouse and human SIGLEC1, position 133 in mouse PILRα and position 126 in human PILRα. We observe that PILRα/ligand interactions require conserved PILRα Arg-133 (mouse) and Arg-126 (human), in correspondence with a previously reported requirement for SIGLEC1 Arg-197 in SIGLEC1/ligand interactions. Homology modeling identifies striking similarities between PILRα and SIGLEC1 ligand binding pockets as well as at least one set of distinctive interactions in the galactoxyl-binding site. Binding studies suggest that PILRα recognizes a complex ligand domain involving both sialic acid and protein motif(s). Thus, PILRα is evolved to engage multiple ligands with common molecular determinants to modulate myeloid cell functions in anatomical settings where PILRα ligands are expressed.

Increased targeting of donor switch region and IgE in Sgamma1-deficient B cells.

Ab class switch recombination involves a recombination between two repetitive DNA sequences known as switch (S) regions that vary in length, content, and density of the repeats. Abs expressed by B cells are diversified by somatic hypermutation and class switch recombination. Both class switch recombination and somatic hypermutation are initiated by activation-induced cytidine deaminase (AID), which preferentially recognizes certain hot spots that are far more enriched in the S regions. We found that removal of the largest S region, Sgamma1 (10 kb), in mice can result in the accumulation of mutations and short-range intra-S recombination in the donor Smu region. Furthermore, elevated levels of IgE were detected in trinitrophenol-OVA-immunized mice and in anti-CD40 plus IL-4-stimulated B cells in vitro. We propose that AID availability and targeting in part might be regulated by its DNA substrate. Thus, prominently transcribed S regions, such as Sgamma1, might provide a sufficient sink for AID protein to titrate away AID from other accessible sites within or outside the Ig locus.

Plasmid-Based Donor Templates for Nonviral CRISPR/Cas9-Mediated Gene Knock-In in Human T Cells.

Effective and precise gene editing of T lymphocytes is critical for advancing the understanding of T cell biology and the development of next-generation cellular therapies. Although methods for effective CRISPR/Cas9-mediated gene knock-out in primary human T cells have been developed, complementary techniques for nonviral gene knock-in can be cumbersome and inefficient. Here, we report a simple and efficient method for nonviral CRISPR/Cas9-based gene knock-in utilizing plasmid-based donor DNA templates. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Purification of human CD4+ or CD8+ T cells from blood Basic Protocol 2: Activation of purified CD4+ or CD8+ T cells using TransAct CD3/CD28 agonist-conjugated nanomatrix Basic Protocol 3: Preparation of Cas9/sgRNA RNPs Basic Protocol 4: Transfection of CAS9-RNP and knock-in template into human T cells Support Protocol 1: Purity check following magnetic T cell isolation Support Protocol 2: Dextramer staining of TCR-edited T cells Support Protocol 3: Functional characterization of TCR knock-in T cells Support Protocol 4: Detection of knock-in reporter activity in CRISPR/CAS9-edited T cells.

High-efficiency nonviral CRISPR/Cas9-mediated gene editing of human T cells using plasmid donor DNA.

Genome engineering of T lymphocytes, the main effectors of antitumor adaptive immune responses, has the potential to uncover unique insights into their functions and enable the development of next-generation adoptive T cell therapies. Viral gene delivery into T cells, which is currently used to generate CAR T cells, has limitations in regard to targeting precision, cargo flexibility, and reagent production. Nonviral methods for effective CRISPR/Cas9-mediated gene knock-out in primary human T cells have been developed, but complementary techniques for nonviral gene knock-in can be cumbersome and inefficient. Here, we report a convenient and scalable nonviral method that allows precise gene edits and transgene integration in primary human T cells, using plasmid donor DNA template and Cas9-RNP. This method is highly efficient for single and multiplex gene manipulation, without compromising T cell function, and is thus valuable for use in basic and translational research.

DNA targets of AID evolutionary link between antibody somatic hypermutation and class switch recombination.

As part of the adaptive immune response, B cells alter their functional immunoglobulin (Ig) receptor genes through somatic hypermutation (SHM) and/or class switch recombination (CSR) via processes that are initiated by activation induced cytidine deaminase (AID). These genetic modifications are targeted at specific sequences known as Variable (V) and Switch (S) regions. Here, we analyze and review the properties and function of AID target sequences across species and compare them with non-Ig sequences, including known translocation hotspots. We describe properties of the S sequences, and discuss species and isotypic differences among S regions. Common properties of SHM and CSR target sequences suggest that evolution of S regions might involve the duplication and selection of SHM hotspots.

DEAF-1 regulates immunity gene expression in Drosophila.

Immunity genes are activated in the Drosophila fat body by Rel and GATA transcription factors. Here, we present evidence that an additional regulatory factor, deformed epidermal autoregulatory factor-1 (DEAF-1), also contributes to the immune response and is specifically important for the induction of two genes encoding antimicrobial peptides, Metchnikowin (Mtk) and Drosomycin (Drs). The systematic mutagenesis of a minimal Mtk 5' enhancer identified a sequence motif essential for both a response to LPS preparations in S2 cells and activation in the larval fat body in response to bacterial infection. Using affinity chromatography coupled to multidimensional protein identification technology (MudPIT), we identified DEAF-1 as a candidate regulator. DEAF-1 activates the expression of Mtk and Drs promoter-luciferase fusion genes in S2 cells. SELEX assays and footprinting data indicate that DEAF-1 binds to and activates Mtk and Drs regulatory DNAs via a TTCGGBT motif. The insertion of this motif into the Diptericin (Dpt) regulatory region confers DEAF-1 responsiveness to this normally DEAF-1-independent enhancer. The coexpression of DEAF-1 with Dorsal, Dif, and Relish results in the synergistic activation of transcription. We propose that DEAF-1 is a regulator of Drosophila immunity.

Embryonic lethality and defective mammary gland development of activator-function impaired conditional knock-in Erbb3 V943R mice.

ERBB3 is a pseudokinase domain-containing member of the ERBB family of receptor tyrosine kinases (RTKs). Following ligand binding, ERBB receptors homo- or hetero-dimerize, leading to a head-to-tail arrangement of the intracellular kinase domains, where the "receiver" kinase domain of one ERBB is activated by the "activator" domain of the other ERBB in the dimer. In ERBB3, a conserved valine at codon 943 (V943) in the kinase C-terminal domain has been shown to be important for its function as an "activator" kinase in vitro. Here we report a knock-in mouse model where we have modified the endogenous Erbb3 allele to allow for tissue-specific conditional expression of Erbb3 V943R (Erbb3 CKI-V943R ). Additionally, we generated an Erbb3 D850N (Erbb3 CKI-D850N ) conditional knock-in mouse model where the conserved aspartate in the DFG motif of the pseudokinase domain was mutated to abolish any potential residual kinase activity. While Erbb3 D850N/D850N animals developed normally, homozygous Erbb3 V943R/V943R expression during development resulted in embryonic lethality. Further, tissue specific expression of Erbb3 V943R/V943R in the mammary gland epithelium following its activation using MMTV-Cre resulted in delayed elongation of the ductal network during puberty. Single-cell RNA-seq analysis of Erbb3 V943R/V943R mammary glands showed a reduction in a specific subset of fibrinogen-producing luminal epithelial cells.

The kinase IRAK4 promotes endosomal TLR and immune complex signaling in B cells and plasmacytoid dendritic cells.

The dysregulation of multiple signaling pathways, including those through endosomal Toll-like receptors (TLRs), Fc gamma receptors (FcγR), and antigen receptors in B cells (BCR), promote an autoinflammatory loop in systemic lupus erythematosus (SLE). Here, we used selective small-molecule inhibitors to assess the regulatory roles of interleukin-1 receptor (IL-1R)-associated kinase 4 (IRAK4) and Bruton's tyrosine kinase (BTK) in these pathways. The inhibition of IRAK4 repressed SLE immune complex- and TLR7-mediated activation of human plasmacytoid dendritic cells (pDCs). Correspondingly, the expression of interferon (IFN)-responsive genes (IRGs) in cells and in mice was positively regulated by the kinase activity of IRAK4. Both IRAK4 and BTK inhibition reduced the TLR7-mediated differentiation of human memory B cells into plasmablasts. TLR7-dependent inflammatory responses were differentially regulated by IRAK4 and BTK by cell type: In pDCs, IRAK4 positively regulated NF-κB and MAPK signaling, whereas in B cells, NF-κB and MAPK pathways were regulated by both BTK and IRAK4. In the pristane-induced lupus mouse model, inhibition of IRAK4 reduced the expression of IRGs during disease onset. Mice engineered to express kinase-deficient IRAK4 were protected from both chemical (pristane-induced) and genetic (NZB/W_F1 hybrid) models of lupus development. Our findings suggest that kinase inhibitors of IRAK4 might be a therapeutic in patients with SLE.

The Indian cobra reference genome and transcriptome enables comprehensive identification of venom toxins.

Snakebite envenoming is a serious and neglected tropical disease that kills ~100,000 people annually. High-quality, genome-enabled comprehensive characterization of toxin genes will facilitate development of effective humanized recombinant antivenom. We report a de novo near-chromosomal genome assembly of Naja naja, the Indian cobra, a highly venomous, medically important snake. Our assembly has a scaffold N50 of 223.35 Mb, with 19 scaffolds containing 95% of the genome. Of the 23,248 predicted protein-coding genes, 12,346 venom-gland-expressed genes constitute the 'venom-ome' and this included 139 genes from 33 toxin families. Among the 139 toxin genes were 19 'venom-ome-specific toxins' (VSTs) that showed venom-gland-specific expression, and these probably encode the minimal core venom effector proteins. Synthetic venom reconstituted through recombinant VST expression will aid in the rapid development of safe and effective synthetic antivenom. Additionally, our genome could serve as a reference for snake genomes, support evolutionary studies and enable venom-driven drug discovery.

Computational models for neurogenic gene expression in the Drosophila embryo.

The early Drosophila embryo is emerging as a premiere model system for the computational analysis of gene regulation in development because most of the genes, and many of the associated regulatory DNAs, that control segmentation and gastrulation are known. The comprehensive elucidation of Drosophila gene networks provides an unprecedented opportunity to apply quantitative models to metazoan enhancers that govern complex patterns of gene expression during development. Models based on the fractional occupancy of defined DNA binding sites have been used to describe the regulation of the lac operon in E. coli and the lysis/lysogeny switch of phage lambda. Here, we apply similar models to enhancers regulated by the Dorsal gradient in the ventral neurogenic ectoderm (vNE) of the early Drosophila embryo. Quantitative models based on the fractional occupancy of Dorsal, Twist, and Snail binding sites raise the possibility that cooperative interactions among these regulatory proteins mediate subtle differences in the vNE expression patterns. Variations in cooperativity may be attributed to differences in the detailed linkage of Dorsal, Twist, and Snail binding sites in vNE enhancers. We propose that binding site occupancy is the key rate-limiting step for establishing localized patterns of gene expression in the early Drosophila embryo.

Function of CSF1 and IL34 in Macrophage Homeostasis, Inflammation, and Cancer.

Colony-stimulating factor 1 (CSF1) and interleukin 34 (IL34) signal via the CSF1 receptor to regulate macrophage differentiation. Studies in IL34- or CSF1-deficient mice have revealed that IL34 function is limited to the central nervous system and skin during development. However, the roles of IL34 and CSF1 at homeostasis or in the context of inflammatory diseases or cancer in wild-type mice have not been clarified in vivo. By neutralizing CSF1 and/or IL34 in adult mice, we identified that they play important roles in macrophage differentiation, specifically in steady-state microglia, Langerhans cells, and kidney macrophages. In several inflammatory models, neutralization of both CSF1 and IL34 contributed to maximal disease protection. However, in a myeloid cell-rich tumor model, CSF1 but not IL34 was required for tumor-associated macrophage accumulation and immune homeostasis. Analysis of human inflammatory conditions reveals IL34 upregulation that may account for the protection requirement of IL34 blockade. Furthermore, evaluation of IL34 and CSF1 blockade treatment during Listeria infection reveals no substantial safety concerns. Thus, IL34 and CSF1 play non-redundant roles in macrophage differentiation, and therapeutic intervention targeting IL34 and/or CSF1 may provide an effective treatment in macrophage-driven immune-pathologies.

Actionable Activating Oncogenic ERBB2/HER2 Transmembrane and Juxtamembrane Domain Mutations.

Deregulated HER2 is a target of many approved cancer drugs. We analyzed 111,176 patient tumors and identified recurrent mutations in HER2 transmembrane domain (TMD) and juxtamembrane domain (JMD) that include G660D, R678Q, E693K, and Q709L. Using a saturation mutagenesis screen and testing of patient-derived mutations we found several activating TMD and JMD mutations. Structural modeling and analysis showed that the TMD/JMD mutations function by improving the active dimer interface or stabilizing an activating conformation. Further, we found that HER2 G660D employed asymmetric kinase dimerization for activation and signaling. Importantly, anti-HER2 antibodies and small-molecule kinase inhibitors blocked the activity of TMD/JMD mutants. Consistent with this, a G660D germline mutant lung cancer patient showed remarkable clinical response to HER2 blockade.

CtBP-independent repression in the Drosophila embryo.

There are three mechanisms of transcriptional repression in eukaryotes. The first is quenching, whereby repressors and activators co-occupy closely linked sites and then the repressor inhibits adjacent activators. The second is direct repression, in which repressors block the function of the core transcription complex. The third is competition, in which repressors compete with activators for a common DNA-binding site. Previous studies have shown that the Drosophila melanogaster CtBP corepressor (dCtBP) is essential for the quenching activity of three short-range sequence-specific repressors in the early Drosophila embryo: Krüppel, Knirps, and Snail. Here we demonstrate that dCtBP is dispensable for target enhancers that contain overlapping activator and repressor binding sites. However, it is essential when Krüppel and Knirps repressor sites do not overlap activator sites but are instead located adjacent to either activators or the core promoter. These findings provide evidence that competition is distinct from quenching and direct repression. Quenching and direct repression depend on dCtBP, whereas competition does not.

The kinase TPL2 activates ERK and p38 signaling to promote neutrophilic inflammation.

Tumor progression locus 2 (TPL2; also known as MAP3K8) is a mitogen-activated protein kinase (MAPK) kinase kinase (MAP3K) that phosphorylates the MAPK kinases MEK1 and MEK2 (MEK1/2), which, in turn, activate the MAPKs extracellular signal-regulated kinase 1 (ERK1) and ERK2 (ERK1/2) in macrophages stimulated through the interleukin-1 receptor (IL-1R), Toll-like receptors (TLRs), or the tumor necrosis factor receptor (TNFR). We describe a conserved and critical role for TPL2 in mediating the effector functions of neutrophils through the activation of the p38 MAPK signaling pathway. Gene expression profiling and functional studies of neutrophils and monocytes revealed a MEK1/2-independent branch point downstream of TPL2 in neutrophils. Biochemical analyses identified the MAPK kinases MEK3 and MEK6 and the MAPKs p38α and p38δ as downstream effectors of TPL2 in these cells. Genetic ablation of the catalytic activity of TPL2 or therapeutic intervention with a TPL2-specific inhibitor reduced the production of inflammatory mediators by neutrophils in response to stimulation with the TLR4 agonist lipopolysaccharide (LPS) in vitro, as well as in rodent models of inflammatory disease. Together, these data suggest that TPL2 is a drug target that activates not only MEK1/2-dependent but also MEK3/6-dependent signaling to promote inflammatory responses.

Antibody Isotype Switching in Vertebrates.

The humoral or antibody-mediated immune response in vertebrates has evolved to respond to diverse antigenic challenges in various anatomical locations. Diversification of the immunoglobulin heavy chain (IgH) constant region via isotype switching allows for remarkable plasticity in the immune response, including versatile tissue distribution, Fc receptor binding, and complement fixation. This enables antibody molecules to exert various biological functions while maintaining antigen-binding specificity. Different immunoglobulin (Ig) classes include IgM, IgD, IgG, IgE, and IgA, which exist as surface-bound and secreted forms. High-affinity autoantibodies are associated with various autoimmune diseases such as lupus and arthritis, while defects in components of isotype switching are associated with infections. A major route of infection used by a large number of pathogens is invasion of mucosal surfaces within the respiratory, digestive, or urinary tract. Most infections of this nature are initially limited by effector mechanisms such as secretory IgA antibodies. Mucosal surfaces have been proposed as a major site for the genesis of adaptive immune responses, not just in fighting infections but also in tolerating commensals and constant dietary antigens. We will discuss the evolution of isotype switching in various species and provide an overview of the function of various isotypes with a focus on IgA, which is universally important in gut homeostasis as well as pathogen clearance. Finally, we will discuss the utility of antibodies as therapeutic modalities.

Inhibition of the kinase ITK in a mouse model of asthma reduces cell death and fails to inhibit the inflammatory response.

Interleukin-2 (IL-2)-inducible T cell kinase (ITK) mediates T cell receptor (TCR) signaling primarily to stimulate the production of cytokines, such as IL-4, IL-5, and IL-13, from T helper 2 (TH2) cells. Compared to wild-type mice, ITK knockout mice are resistant to asthma and exhibit reduced lung inflammation and decreased amounts of TH2-type cytokines in the bronchoalveolar lavage fluid. We found that a small-molecule selective inhibitor of ITK blocked TCR-mediated signaling in cultured TH2 cells, including the tyrosine phosphorylation of phospholipase C-γ1 (PLC-γ1) and the secretion of IL-2 and TH2-type cytokines. Unexpectedly, inhibition of the kinase activity of ITK during or after antigen rechallenge in an ovalbumin-induced mouse model of asthma failed to reduce airway hyperresponsiveness and inflammation. Rather, in mice, pharmacological inhibition of ITK resulted in T cell hyperplasia and the increased production of TH2-type cytokines. Thus, our studies predict that inhibition of the kinase activity of ITK may not be therapeutic in patients with asthma.

Critical role of activation induced cytidine deaminase in experimental autoimmune encephalomyelitis.

Multiple Sclerosis (MS) is a neurodegenerative autoimmune disorder caused by chronic inflammation and demyelination within the central nervous system (CNS). Clinical studies in MS patients have demonstrated efficacy with B cell targeted therapies such as anti-CD20. However, the exact role that B cells play in the disease process is unclear. Activation Induced cytidine deaminase (AID) is an essential enzyme for the processes of antibody affinity maturation and isotype switching. To evaluate the impact of affinity maturation and isotype switching, we have interrogated the effect of AID-deficiency in an animal model of MS. Here, we show that the severity of experimental autoimmune encephalomyelitis (EAE) induced by the extracellular domain of human myelin oligodendrocyte glycoprotein (MOG1-125) is significantly reduced in Aicda deficient mice, which, unlike wild-type mice, lack serum IgG to myelin associated antigens. MOG specific T cell responses are comparable between wild-type and Aicda knockout mice suggesting an active role for antigen experienced B cells. Thus affinity maturation and/or class switching are critical processes in the pathogenesis of EAE.

Origin of immunoglobulin isotype switching.

BACKGROUND: From humans to frogs, immunoglobulin class switching introduces different effector functions to antibodies through an intrachromosomal DNA recombination process at the heavy-chain locus. Although there are two conventional antibody classes (IgM, IgW) in sharks, their heavy chains are encoded by 20 to >100 miniloci. These representatives of the earliest jawed vertebrates possess a primordial immunoglobulin gene organization where each gene cluster is autonomous and contains a few rearranging gene segments (VH-D1-D2-JH) with one constant region, µ or ω. RESULTS: V(D)J rearrangement always takes place within the µ cluster, but here we show that the VDJ can be expressed with constant regions from different clusters, although IgH genes are spatially distant, at >120 kb. Moreover, reciprocal exchanges take place between Igω and Igµ genes. Switching is augmented with deliberate immunization and is concomitant with somatic hypermutation activity. Because switching occurs independently of the partners' linkage position, some events involve transchromosomal recombination. The switch sites consist of direct joins between two genes in the 3' intron flanking JH. CONCLUSIONS: Our data are consistent with a mechanism of cutting or joining of distal DNA lesions initiated by activation-induced cytidine deaminase (AID), in the absence of mammalian-type switch regions. We suggest that, in shark, with its many autonomous IgH targeted by programmed DNA breakage, factors predisposing broken DNA ends to translocate configured the earliest version of class switch recombination.