Nuclear factor κB (NF-κB) activation is a deleterious molecular mechanism that drives acute kidney injury (AKI) and manifests in transplanted kidneys as delayed graft function. The TNFAIP3 gene encodes A20, a cytoplasmic ubiquitin ligase and a master negative regulator of the NF- κB signaling pathway. Common population-specific TNFAIP3 coding variants that reduce A20's enzyme function and increase NF- κB activation have been linked to heightened protective immunity and autoimmune disease, but have not been investigated in AKI. Here, we functionally identified a series of unique human TNFAIP3 coding variants linked to the autoimmune genome-wide association studies single nucleotide polymorphisms of F127C; namely F127C;R22Q, F127C;G281E, F127C;W448C and F127C;N449K that reduce A20's anti-inflammatory function in an NF- κB reporter assay. To investigate the impact of TNFAIP3 hypomorphic coding variants in AKI we tested a mouse Tnfaip3 hypomorph in a model of ischemia reperfusion injury (IRI). The mouse Tnfaip3 coding variant I325N increases NF- κB activation without overt inflammatory disease, providing an immune boost as I325N mice exhibit enhanced innate immunity to a bacterial challenge. Surprisingly, despite exhibiting increased intra-kidney NF- κB activation with inflammation in IRI, the kidney of I325N mice was protected. The I325N variant influenced the outcome of IRI by changing the dynamic expression of multiple cytoprotective mechanisms, particularly by increasing NF- κB-dependent anti-apoptotic factors BCL-2, BCL-XL, c-FLIP and A20, altering the active redox state of the kidney with a reduction of superoxide levels and the enzyme super oxide dismutase-1, and enhancing cellular protective mechanisms including increased Foxp3+ T cells. Thus, TNFAIP3 gene variants represent a kidney and population-specific molecular factor that can dictate the course of IRI.

NF-κB activation unites metabolic and inflammatory responses in many diseases yet less is known about the role NF-κB plays in normal metabolism. Here, to define this role in the context of beta cell function and metabolic control, we deleted the canonical NF-κB transcription factor RelA/p65 specifically in pancreatic beta cells to generate βP65KO mice. RelA deficiency resulted in complete loss of stimulus dependent inflammatory gene upregulation, consistent with its known role to govern inflammation. However, RelA deletion also rendered mice glucose intolerant due to a functional loss of insulin secretion. Glucose intolerance was intrinsic to beta cells as βP65KO islets failed to secrete insulin ex vivo in response to a glucose challenge, and were unable to restore metabolic control when transplanted into secondary diabetic recipients. Maintenance of glucose tolerance required RelA, but was independent of classical NF-κB inflammatory cascades, as blocking NF-κB signalling in vivo by beta cell knock-out of the essential activator of NF-κB, NEMO, or beta cell overexpression of the negative NF-κB regulator, A20, did not cause severe glucose intolerance. Thus, basal RelA activity performs an essential and islet-intrinsic role to maintain normal glucose homeostasis. Genome wide bioinformatic mapping revealed the presence of RelA binding sites in the promoter regions of specific metabolic genes, and in the majority (~70%) of islet enhancer hubs that are responsible for shaping beta cell type-specific gene expression programmes. Indeed, islet specific metabolic genes Slc2a2 and Capn9, identified within the large network of islet enhancer hub genes showed dysregulated expression in βP65KO islets. These data demonstrate an unappreciated role for RelA as a regulator of islet-specific transcriptional programmes necessary for the maintenance of healthy glucose metabolism.

ABSTRACTMonogenic diseases can often manifest diverse clinical phenotypes and cause diagnostic dilemmas. While monoallelic loss-of-function variants in TNFAIP3 (Haploinsufficiency of A20; HA20) cause a highly penetrant autoinflammatory disease, the variable expressivity suggest a role for additional genetic and environmental disease modifiers. Here, we identify critically ill children who inherited a family-specific TNFAIP3 deletion from one of their otherwise healthy parents. Each of the probands also inherited in trans a subtle loss-of-function I207L TNFAIP3 variant that is common in Oceania, originally introgressed from Denisovans. Modelling this compound heterozgous state in mice under specific pathogen free conditions demonstrated a reduced threshold to break immune tolerance. Exaggerated immune responses were precipitated by inheriting the two genetic hits on the TNFAIP3 checkpoint coupled with increasing the microbial challenge to immune tolerance, either by co-housing with pet store mice carrying a wild microbial burden or by transient dietary exposure to a chemical that diminishes the intestinal mucin barrier separating gut microbes from immune sensing systems. These data illuminate second-hit genetic and environmental modifiers contributing to complex inflammatory and autoimmune disease. Increased mechanistic understanding of the presence and contribution of disease modifiers will aid diagnostic and prognostic patient stratification and potentially reveal novel therapeutic opportunities.

Women with autoimmune and inflammatory aetiologies can exhibit reduced fecundity. TNFAIP3 is a master negative regulator of inflammation, and has been linked to many inflammatory conditions by genome wide associations studies, however its role in fertility remains unknown. Here we show that mice harbouring a mild Tnfaip3 reduction-of-function coding variant (Tnfaip3I325N) that reduces the threshold for inflammatory NF-κB activation, exhibit reduced fecundity. Sub-fertility in Tnfaip3I325N mice is associated with irregular estrous cycling, low numbers of ovarian secondary follicles, impaired mammary gland development and insulin resistance. These pathological features are associated with infertility in human subjects. Transplantation of Tnfaip3I325N ovaries, mammary glands or pancreatic islets into wild-type recipients rescued estrous cycling, mammary branching and hyperinsulinemia respectively, pointing towards a cell-extrinsic hormonal mechanism. Examination of hypothalamic brain sections revealed increased levels of microglial activation with reduced levels of luteinizing hormone. TNFAIP3 coding variants may offer one contributing mechanism for the cause of sub-fertility observed across otherwise healthy populations as well as for the wide variety of auto-inflammatory conditions to which TNFAIP3 is associated. Further, TNFAIP3 represents a molecular mechanism that links heightened immunity with neuronal inflammatory homeostasis. These data also highlight that tuning-up immunity with TNFAIP3 comes with the potentially evolutionary significant trade-off of reduced fertility.

The notion that mobile units of nucleic acid known as transposable elements can operate as genomic controlling elements was put forward over six decades ago(1,2). However, it was not until the advancement of genomic sequencing technologies that the abundance and repertoire of transposable elements were revealed, and they are now known to constitute up to two-thirds of mammalian genomes(3,4). The presence of DNA regulatory regions including promoters, enhancers and transcription-factor-binding sites within transposable elements(5-8) has led to the hypothesis that transposable elements have been co-opted to regulate mammalian gene expression and cell phenotype(8-14). Mammalian transposable elements include recent acquisitions and ancient transposable elements that have been maintained in the genome over evolutionary time. The presence of ancient conserved transposable elements correlates positively with the likelihood of a regulatory function, but functional validation remains an essential step to identify transposable element insertions that have a positive effect on fitness. Here we show that CRISPR-Cas9-mediated deletion of a transposable element-namely the LINE-1 retrotransposon Lx9c11-in mice results in an exaggerated and lethal immune response to virus infection. Lx9c11 is critical for the neogenesis of a non-coding RNA (Lx9c11-RegoS) that regulates genes of the Schlafen family, reduces the hyperinflammatory phenotype and rescues lethality in virus-infected Lx9c11(-/-) mice. These findings provide evidence that a transposable element can control the immune system to favour host survival during virus infection.

Background Neonatal porcine islets (NPIs) can restore glucose control in mice, pigs, and non-human primates, representing a potential abundant alternative islet supply for clinical beta cell replacement therapy. However, NPIs are vulnerable to inflammatory insults that could be overcome with genetic modifications. Here, we demonstrate in a series of proof-of-concept experiments the potential of the cytoplasmic ubiquitin-editing protein A20, encoded by the TNFAIP3 gene, as an NPI cytoprotective gene. Methods We forced A20 expression in NPI grafts using a recombinant adenovirus 5 (Ad5) vector and looked for impact on TNF-stimulated NF-kappa B activation and NPI graft function. As adeno-associated vectors (AAV) are clinically preferred vectors but exhibit poor transduction efficacy in NPIs, we next screened a series of AAV serotypes under different transduction protocols for their ability achieve high transduction efficiency and suppress NPI inflammation without impacting NPI maturation. Results Forcing the expression of A20 in NPI with Ad5 vector blocked NF-kappa B activation by inhibiting I kappa B alpha phosphorylation and degradation, and reduced the induction of pro-inflammatory genes Cxcl10 and Icam1. A20-expressing NPIs also exhibited superior functional capacity when transplanted into diabetic immunodeficient recipient mice, evidenced by a more rapid return to euglycemia and improved GTT compared to unmodified NPI grafts. We found AAV2 combined with a 14-day culture period maximized NPI transduction efficiency (>70% transduction rate), and suppressed NF-kappa B-dependent gene expression without adverse impact upon NPI maturation. Conclusion We report a new protocol that allows for high-efficiency genetic modification of NPIs, which can be utilized to introduce candidate genes without the need for germline engineering. This approach would be suitable for preclinical and clinical testing of beneficial molecules. We also report for the first time that A20 is cytoprotective for NPI, such that A20 gene therapy could aid the clinical development of NPIs for beta cell replacement.

The CRISPR-Cas9 and related systems offer a unique genome-editing tool allowing facile and efficient introduction of heritable and locus-specific sequence modifications in the genome. Despite its molecular precision, temporal and spatial control of gene editing with the CRISPR-Cas9 system is very limited. We developed a light-sensitive liposome delivery system that offers a high degree of spatial and temporal control of gene editing with the CRISPR-Cas9 system. We demonstrated its efficient protein release by respectively assessing the targeted knockout of the eGFP gene in human HEK293/GFP cells and the TNFAIP3 gene in TNFα-induced HEK293 cells. We further validated our results at a single-cell resolution using an in vivo eGFP reporter system in zebrafish (77% knockout). These findings indicate that light-triggered liposomes may have new options for precise control of CRISPR-Cas9 release and editing.

Germline loss-of-function variation in TNFAIP3 , encoding A20, has been implicated in a wide variety of autoinflammatory and autoimmune conditions, with acquired somatic missense mutations linked to cancer progression. Furthermore, human sequence data reveals that the A20 locus contains ~ 400 non-synonymous coding variants, which are largely uncharacterised. The growing number of A20 coding variants with unknown function, but potential clinical impact, poses a challenge to traditional mouse-based approaches. Here we report the development of a novel functional genomics approach that utilizes a new A20-deficient zebrafish ( Danio rerio ) model to investigate the impact of TNFAIP3 genetic variants in vivo. A20-deficient zebrafish are hyper-responsive to microbial immune activation and exhibit spontaneous early lethality. Ectopic addition of human A20 rescued A20-null zebrafish from lethality, while missense mutations at two conserved A20 residues, S381A and C243Y, reversed this protective effect. Ser381 represents a phosphorylation site important for enhancing A20 activity that is abrogated by its mutation to alanine, or by a causal C243Y mutation that triggers human autoimmune disease. These data reveal an evolutionarily conserved role for TNFAIP3 in limiting inflammation in the vertebrate linage and show how this function is controlled by phosphorylation. They also demonstrate how a zebrafish functional genomics pipeline can be utilized to investigate the in vivo significance of medically relevant human TNFAIP3 gene variants.

Islet transplantation can restore lost glycemic control in type 1 diabetes subjects, but is restricted in its clinical application by limiting supplies of islets and the need for heavy immune suppression to prevent rejection. TNFAIP3 , encoding the ubiquitin editing enzyme A20, regulates the activation of immune cells by raising NF-κB signalling thresholds. Here we show that increasing A20 expression in allogeneic islet grafts resulted in permanent survival for ~45 % of recipients, and >80% survival when combined with subtherapeutic rapamycin. Allograft survival was dependent upon regulatory T cells, was antigen-specific and grafts showed reduced expression of inflammatory factors, but increased TGFβ and IL-10. By analysing islets expressing an A20 coding mutation (I325N) that cripples A20’s OTU ubiquitin editing domain, we found that A20 regulates intra-graft RIPK1 levels to modulate NF-κB signalling. Transplantation of I325N islets resulted in increased NF-κB signalling, graft hyper-inflammation and acute allograft rejection. Neonatal porcine islets (NPI) represent a clinical alternative islet source but are readily rejected. However, forced A20 expression reduced NPI inflammation and increased their function after transplantation. Therapeutic administration of A20 raises NF-κB signalling thresholds and promotes islet allogeneic survival. Clinically this would allow for reduced immunosuppression supporting the use of alternate islet sources.

Resisting and tolerating microbes are alternative strategies to survive infection, but little is known about the evolutionary mechanisms controlling this balance. Here genomic analyses of anatomically modern humans, extinct Denisovan hominins and mice revealed a TNFAIP3 allelic series with alterations in the encoded immune response inhibitor A20. Each TNFAIP3 allele encoded substitutions at non-catalytic residues of the ubiquitin protease OTU domain that diminished IκB kinase-dependent phosphorylation and activation of A20. Two TNFAIP3 alleles encoding A20 proteins with partial phosphorylation deficits seemed to be beneficial by increasing immunity without causing spontaneous inflammatory disease: A20 T108A;I207L, originating in Denisovans and introgressed in modern humans throughout Oceania, and A20 I325N, from an N -ethyl- N -nitrosourea (ENU)-mutagenized mouse strain. By contrast, a rare human TNFAIP3 allele encoding an A20 protein with 95% loss of phosphorylation, C243Y, caused spontaneous inflammatory disease in humans and mice. Analysis of the partial-phosphorylation A20 I325N allele in mice revealed diminished tolerance of bacterial lipopolysaccharide and poxvirus inoculation as tradeoffs for enhanced immunity.

Resisting or tolerating microbes are alternative strategies to survive infection, but little is known about the evolutionary mechanisms controlling this balance. Here, genomic analyses of anatomically modern humans, extinct Denisovan hominins, and mice revealed a series of missense variants in the immune response inhibitor A20 (encoded by TNFAIP3 ), substituting non-catalytic residues of the ubiquitin protease domain to diminish IκB-dependent phosphorylation and activation of A20. Two A20 variants with partial phosphorylation deficits appeared beneficial: one originating in Denisovans and introgressed in modern humans throughout Oceania, and another in a mouse strain resistant to Coxsackievirus. By contrast, a variant with 95% loss of phosphorylation caused spontaneous inflammatory disease in humans and mice. Analysis of the partial phosphorylation variant in mice revealed diminished tolerance of bacterial lipopolysaccharide or to poxvirus inoculation as trade-offs for enhanced immunity. One Sentence Summary Modern and ancient variants reveal a genetically tunable element for balancing immunity and microbial tolerance.

Purpose of review Clinical islet transplantation does not enjoy the success seen for solid organ transplants, indicating a need for new therapeutic approaches to improve patient outcomes. This has prompted investigation into islet autonomous factors and pathways that may represent druggable targets. These have the potential to synergize with approaches aimed at generating graft-specific tolerance. Recent findings There are emerging data that nuclear factor B (NF-kappa B) activation can prevent and or overcome tolerance, whereas dampening NF-kappa B activation in immune cells is associated with prolonged allograft survival. In islet cells, NF-kappa B plays a central role in triggering the inflammatory transcriptional response that is often associated with reduced islet function and contributes to poor transplant outcomes. Summary Targeting intraislet NF-kappa B represents a promising target in islet transplantation. Here we will discuss the current state of the knowledge on the role of NF-kappa B activation in the context of islet transplantation and the implications of targeting NF-kappa B for tolerance induction.

Clinical islet transplantation does not enjoy the success seen for solid organ transplants, indicating a need for new therapeutic approaches to improve patient outcomes. This has prompted investigation into islet autonomous factors and pathways that may represent druggable targets. These have the potential to synergize with approaches aimed at generating graft-specific tolerance.There are emerging data that nuclear factor κB (NF-κB) activation can prevent and or overcome tolerance, whereas dampening NF-κB activation in immune cells is associated with prolonged allograft survival. In islet cells, NF-κB plays a central role in triggering the inflammatory transcriptional response that is often associated with reduced islet function and contributes to poor transplant outcomes.Targeting intraislet NF-κB represents a promising target in islet transplantation. Here we will discuss the current state of the knowledge on the role of NF-κB activation in the context of islet transplantation and the implications of targeting NF-κB for tolerance induction.

Influenza A virus (IAV) infections lead to severe inflammation in the airways. Patients with chronic obstructive pulmonary disease (COPD) characteristically have exaggerated airway inflammation and are more susceptible to infections with severe symptoms and increased mortality. The mechanisms that control inflammation during IAV infection and the mechanisms of immune dysregulation in COPD are unclear. We found that IAV infections lead to increased inflammatory and antiviral responses in primary bronchial epithelial cells (pBECs) from healthy nonsmoking and smoking subjects. In pBECs from COPD patients, infections resulted in exaggerated inflammatory but deficient antiviral responses. A20 is an important negative regulator of NF-κB-mediated inflammatory but not antiviral responses, and A20 expression was reduced in COPD. IAV infection increased the expression of miR-125a or -b, which directly reduced the expression of A20 and mitochondrial antiviral signaling (MAVS), and caused exaggerated inflammation and impaired antiviral responses. These events were replicated in vivo in a mouse model of experimental COPD. Thus, miR-125a or -b and A20 may be targeted therapeutically to inhibit excessive inflammatory responses and enhance antiviral immunity in IAV infections and in COPD.

beta cell replacement with either pancreas or islet transplantation has progressed immensely over the last decades with current 1- and 5-year insulin independence rates of approximately 85% and 50%, respectively. Recent advances are largely attributed to improvements in immunosuppressive regimen, donor selection, and surgical technique. However, both strategies are compromised by a scarce donor source. Xenotransplantation offers a potential solution by providing a theoretically unlimited supply of islets, but clinical application has been limited by concerns for a potent immune response against xenogeneic tissue. beta cell clusters derived from embryonic or induced pluripotent stem cells represent another promising unlimited source of insulin producing cells, but clinical application is pending further advances in the function of the beta cell like clusters. Exciting developments and rapid progress in all areas of beta cell replacement prompted a lively debate by members of the young investigator committee of the International Pancreas and Islet Transplant Association at the 15th International Pancreas and Islet Transplant Association Congress in Melbourne and at the 26th international congress of The Transplant Society in Hong Kong. This international group of young investigators debated which modality of beta cell replacement would predominate the landscape in 10 years, and their arguments are summarized here.

ß cell replacement with either pancreas or islet transplantation has progressed immensely over the last decades with current 1and 5-year insulin independence rates of ~85% and ~50%, respectively. Recent advances are largely attributed to improvements in immunosuppressive regimen, donor selection and surgical technique. However, both strategies are compromised by a scarce donor source. Xenotransplantation provides a potential solution by providing a theoretically unlimited supply of islets, but clinical application has been limited by concerns for a potent immune response against xenogeneic tissue. ß cell clusters derived from embryonic or induced pluripotent stem (iPS) cells represent another promising unlimited source of insulin producing cells, but clinical application is pending further advances in the function of the ß cell like clusters. Exciting developments and rapid progress in all areas of ß cell replacement prompted a lively debate by members of the young investigator committee of the International Pancreas and Islet Transplant Association (IPITA) at the 15th IPITA Congress in Melbourne and at the 26th [...] SCHUETZ, Christian, et al. ß cell replacement therapy: the next 10 years. Transplantation,

Administration of anti-CD40 ligand (CD40L) antibodies has been reported to allow long-term islet allograft survival in non-human primates without the need for exogenous immunosuppression. However, the use of anti-CD40L antibodies was associated with thromboembolic complications. Targeting downstream intracellular components shared between CD40 and other TNF family co-stimulatory molecules could bypass these complications. TNF receptor associated factor 2 (TRAF2) integrates multiple TNF receptor family signalling pathways that are critical for T cell activation and may be a central node of alloimmune responses.

In this study, a critical and novel role for TNF receptor (TNFR) associated factor 2 (TRAF2) is elucidated for peripheral CD8+ T‐cell and NKT‐cell homeostasis. Mice deficient in TRAF2 only in their T cells (TRAF2TKO) show ∼40% reduction in effector memory and ∼50% reduction in naïve CD8+ T‐cell subsets. IL‐15‐dependent populations were reduced further, as TRAF2TKO mice displayed a marked ∼70% reduction in central memory CD8+CD44hiCD122+ T cells and ∼80% decrease in NKT cells. TRAF2TKO CD8+CD44hi T cells exhibited impaired dose‐dependent proliferation to exogenous IL‐15. In contrast, TRAF2TKO CD8+ T cells proliferated normally to anti‐CD3 and TRAF2TKO CD8+CD44hi T cells exhibited normal proliferation to exogenous IL‐2. TRAF2TKO CD8+ T cells expressed normal levels of IL‐15‐associated receptors and possessed functional IL‐15‐mediated STAT5 phosphorylation, however TRAF2 deletion caused increased AKT activation. Loss of CD8+CD44hiCD122+ and NKT cells was mechanistically linked to an inability to respond to IL‐15. The reduced CD8+CD44hiCD122+ T‐cell and NKT‐cell populations in TRAF2TKO mice were rescued in the presence of high dose IL‐15 by IL‐15/IL‐15Rα complex administration. These studies demonstrate a critical role for TRAF2 in the maintenance of peripheral CD8+ CD44hiCD122+ T‐cell and NKT‐cell homeostasis by modulating sensitivity to T‐cell intrinsic growth factors such as IL‐15.

Citation for published version (APA): Malle, E. K., Zammit, N. W., Walters, S. N., Koay, Y. C., Wu, J., Tan, B. M., Villanueva, J. E., Brink, R., Loudovaris, T., Cantley, J., McAlpine, S. R., Hesselson, D., & Grey, S. T. (2015). Nuclear factor B-inducing kinase activation as a mechanism of pancreatic cell failure in obesity. Journal of Experimental Medicine, 212(8), 1239-1254. https://doi.org/10.1084/jem.20150218