A regulatory element associated to NAFLD in the promoter of DIO1 controls LDL-C, HDL-C and triglycerides in hepatic cells.

BACKGROUND: Genome-wide association studies (GWAS) have identified genetic variants linked to fat metabolism and related traits, but rarely pinpoint causative variants. This limitation arises from GWAS not considering functional implications of noncoding variants that can affect transcription factor binding and potentially regulate gene expression. The aim of this study is to investigate a candidate noncoding functional variant within a genetic locus flagged by a GWAS SNP associated with non-alcoholic fatty liver disease (NAFLD), a condition characterized by liver fat accumulation in non-alcohol consumers. METHODS: CRISPR-Cas9 gene editing in HepG2 cells was used to modify the regulatory element containing the candidate functional variant linked to NAFLD. Global gene expression in mutant cells was assessed through RT-qPCR and targeted transcriptomics. A phenotypic assay measured lipid droplet accumulation in the CRISPR-Cas9 mutants. RESULTS: The candidate functional variant, rs2294510, closely linked to the NAFLD-associated GWAS SNP rs11206226, resided in a regulatory element within the DIO1 gene's promoter region. Altering this element resulted in changes in transcription factor binding sites and differential expression of candidate target genes like DIO1, TMEM59, DHCR24, and LDLRAD1, potentially influencing the NAFLD phenotype. Mutant HepG2 cells exhibited increased lipid accumulation, a hallmark of NAFLD, along with reduced LDL-C, HDL-C and elevated triglycerides. CONCLUSIONS: This comprehensive approach, that combines genome editing, transcriptomics, and phenotypic assays identified the DIO1 promoter region as a potential enhancer. Its activity could regulate multiple genes involved in the NAFLD phenotype or contribute to defining a polygenic risk score for enhanced risk assessment in NAFLD patients.

Organ-specific metabolic pathways distinguish prediabetes, type 2 diabetes, and normal tissues.

Environmental and genetic factors cause defects in pancreatic islets driving type 2 diabetes (T2D) together with the progression of multi-tissue insulin resistance. Mass spectrometry proteomics on samples from five key metabolic tissues of a cross-sectional cohort of 43 multi-organ donors provides deep coverage of their proteomes. Enrichment analysis of Gene Ontology terms provides a tissue-specific map of altered biological processes across healthy, prediabetes (PD), and T2D subjects. We find widespread alterations in several relevant biological pathways, including increase in hemostasis in pancreatic islets of PD, increase in the complement cascade in liver and pancreatic islets of PD, and elevation in cholesterol biosynthesis in liver of T2D. Our findings point to inflammatory, immune, and vascular alterations in pancreatic islets in PD that are hypotheses to be tested for potential contributions to hormonal perturbations such as impaired insulin and increased glucagon production. This multi-tissue proteomic map suggests tissue-specific metabolic dysregulations in T2D.

CD44 Depletion in Glioblastoma Cells Suppresses Growth and Stemness and Induces Senescence.

Glioblastoma multiforme (GBM) is a lethal brain tumor, characterized by enhanced proliferation and invasion, as well as increased vascularization and chemoresistance. The expression of the hyaluronan receptor CD44 has been shown to correlate with GBM progression and poor prognosis. Here, we sought to elucidate the molecular mechanisms by which CD44 promotes GBM progression by knocking out (KO) CD44, employing CRISPR/Cas9 gene editing in U251MG cells. CD44-depleted cells exhibited an impaired proliferation rate, as shown by the decreased cell numbers, decreased Ki67-positive cell nuclei, diminished phosphorylation of CREB, and increased levels of the cell cycle inhibitor p16 compared to control cells. Furthermore, the CD44 KO cells showed decreased stemness and increased senescence, which was manifested upon serum deprivation. In stem cell-like enriched spheres, RNA-sequencing analysis of U251MG cells revealed a CD44 dependence for gene signatures related to hypoxia, the glycolytic pathway, and G2 to M phase transition. Partially similar results were obtained when cells were treated with the γ-secretase inhibitor DAPT, which inhibits CD44 cleavage and therefore inhibits the release of the intracellular domain (ICD) of CD44, suggesting that certain transcriptional responses are dependent on CD44-ICD. Interestingly, the expression of molecules involved in hyaluronan synthesis, degradation, and interacting matrix proteins, as well as of platelet-derived growth factor (PDGF) isoforms and PDGF receptors, were also deregulated in CD44 KO cells. These results were confirmed by the knockdown of CD44 in another GBM cell line, U2990. Notably, downregulation of hyaluronan synthase 2 (HAS2) impaired the hypoxia-related genes and decreased the CD44 protein levels, suggesting a CD44/hyaluronan feedback circuit contributing to GBM progression.

Deubiquitinating enzymes USP4 and USP17 finetune the trafficking of PDGFRß and affect PDGF-BB-induced STAT3 signalling.

Interaction of platelet-derived growth factor (PDGF) isoforms with their receptors results in activation and internalization of receptors, with a concomitant activation of downstream signalling pathways. Ubiquitination of PDGFRs serves as a mark to direct the internalization and sorting of the receptors. By overexpressing a panel of deubiquitinating enzymes (DUBs), we found that USP17 and USP4 efficiently deubiquitinate PDGF receptor ß (PDGFRß) and are able to remove both Lys63 and Lys48-linked polyubiquitin chains from the receptor. Deubiquitination of PDGFRß did not affect its stability, but regulated the timing of its trafficking, whereby USP17 prolonged the presence of the receptor at the cell surface, while USP4 affected the speed of trafficking towards early endosomes. Induction of each of the DUBs in BJhTERT fibroblasts and U2OS osteosarcoma cells led to prolonged and/or shifted activation of STAT3 in response to PDGF-BB stimulation, which in turn led to increased transcriptional activity of STAT3. Induction of USP17 promoted acute upregulation of the mRNA expression of STAT3-inducible genes STAT3, CSF1, junB and c-myc, while causing long-term changes in the expression of myc and CDKN1A. Deletion of USP17 was lethal to fibroblasts, while deletion of USP4 led to a decreased proliferative response to stimulation by PDGF-BB. Thus, USP17- and USP4-mediated changes in ubiquitination of PDFGRß lead to dysregulated signalling and transcription downstream of STAT3, resulting in defects in the control of cell proliferation.

SIDT1 plays a key role in type I IFN responses to nucleic acids in plasmacytoid dendritic cells and mediates the pathogenesis of an imiquimod-induced psoriasis model.

BACKGROUND: Type I IFN (IFN-I) is a family of cytokines involved in the pathogenesis of autoimmune and autoinflammatory diseases such as psoriasis. SIDT1 is an ER-resident protein expressed in the lymphoid lineage, and involved in anti-viral IFN-I responses in vivo, through an unclear mechanism. Herein we have dissected the role of SIDT1 in the natural IFN-producing cells, the plasmacytoid dendritic cells (pDC). METHODS: The function of SIDT1 in pDC was determined by silencing its expression in human primary pDC and GEN2.2 cell line. SIDT1 role in vivo was assessed using the imiquimod-induced psoriasis model in the SIDT1-deficient mice (sidt1-/-). FINDINGS: Silencing of SIDT1 in GEN2.2 led to a blockade of the IFN-I response after stimulation of TLR7 and TLR9, without affecting the pro-inflammatory responses or upregulation of maturation markers. We found that SIDT1 migrates from the ER to the endosomal and lysosomal compartments together with TLR9 after CpG stimulation, participating in the access of the TLR9-CpG complex to lysosome-related vesicles, and therefore mediating the activation of TBK1 and the nuclear migration of IRF7, but not of NF-κB. sidt1-/- mice showed a significant decrease in severity parameters of the imiquimod-induced acute psoriasis-like model, associated with a decrease in the production of IFN-I and IFN-dependent chemokines. INTERPRETATION: Our findings indicate that SIDT1 is at the cross-road between the IFN-I and the proinflammatory pathways and constitutes a promising drug target for psoriasis and other diseases mediated by IFN-I responses. FUNDING: This work was supported by the Consejería de Salud y Familias de la Junta de Andalucía (PIER_S1149 and C2_S0050) and Instituto de Salud Carlos III (PI18/00082 and PI21/01151), partly supported by European FEDER funds, and prior funding to MEAR from the Alliance for Lupus Research and the Swedish Research Council.

Monoallelic and bi-allelic variants in NCDN cause neurodevelopmental delay, intellectual disability, and epilepsy.

Neurochondrin (NCDN) is a cytoplasmatic neural protein of importance for neural growth, glutamate receptor (mGluR) signaling, and synaptic plasticity. Conditional loss of Ncdn in mice neural tissue causes depressive-like behaviors, impaired spatial learning, and epileptic seizures. We report on NCDN missense variants in six affected individuals with variable degrees of developmental delay, intellectual disability (ID), and seizures. Three siblings were found homozygous for a NCDN missense variant, whereas another three unrelated individuals carried different de novo missense variants in NCDN. We assayed the missense variants for their capability to rescue impaired neurite formation in human neuroblastoma (SH-SY5Y) cells depleted of NCDN. Overexpression of wild-type NCDN rescued the neurite-phenotype in contrast to expression of NCDN containing the variants of affected individuals. Two missense variants, associated with severe neurodevelopmental features and epilepsy, were unable to restore mGluR5-induced ERK phosphorylation. Electrophysiological analysis of SH-SY5Y cells depleted of NCDN exhibited altered membrane potential and impaired action potentials at repolarization, suggesting NCDN to be required for normal biophysical properties. Using available transcriptome data from human fetal cortex, we show that NCDN is highly expressed in maturing excitatory neurons. In combination, our data provide evidence that bi-allelic and de novo variants in NCDN cause a clinically variable form of neurodevelopmental delay and epilepsy, highlighting a critical role for NCDN in human brain development.

Proof-of-concept for CRISPR/Cas9 gene editing in human preadipocytes: Deletion of FKBP5 and PPARG and effects on adipocyte differentiation and metabolism.

CRISPR/Cas9 has revolutionized the genome-editing field. So far, successful application in human adipose tissue has not been convincingly shown. We present a method for gene knockout using electroporation in preadipocytes from human adipose tissue that achieved at least 90% efficiency without any need for selection of edited cells or clonal isolation. We knocked out the FKBP5 and PPARG genes in preadipocytes and studied the resulting phenotypes. PPARG knockout prevented differentiation into adipocytes. Conversely, deletion of FKBP51, the protein coded by the FKBP5 gene, did not affect adipogenesis. Instead, it markedly modulated glucocorticoid effects on adipocyte glucose metabolism and, furthermore, we show some evidence of altered transcriptional activity of glucocorticoid receptors. This has potential implications for the development of insulin resistance and type 2 diabetes. The reported method is simple, easy to adapt, and enables the use of human primary preadipocytes instead of animal adipose cell models to assess the role of key genes and their products in adipose tissue development, metabolism and pathobiology.

CRISPR-Cas9-mediated knockout of SPRY2 in human hepatocytes leads to increased glucose uptake and lipid droplet accumulation.

BACKGROUND: The prevalence of obesity and its comorbidities, including type 2 diabetes mellitus (T2DM), is dramatically increasing throughout the world; however, the underlying aetiology is incompletely understood. Genome-wide association studies (GWAS) have identified hundreds of genec susceptibility loci for obesity and T2DM, although the causal genes and mechanisms are largely unknown. SPRY2 is a candidate gene identified in GWAS of body fat percentage and T2DM, and has recently been linked to insulin production in pancreatic ß-cells. In the present study, we aimed to further understand SPRY2 via functional characterisation in HepG2 cells, an in vitro model of human hepatocytes widely used to investigate T2DM and insulin resistance. METHODS: CRISPR-Cas9 genome editing was used to target SPRY2 in HepG2 cells, and the functional consequences of SPRY2 knockout (KO) and overexpression subsequently assessed using glucose uptake and lipid droplet assays, measurement of protein kinase phosphorylation and RNA sequencing. RESULTS: The major functional consequence of SPRY2 KO was a significant increase in glucose uptake, along with elevated lipid droplet accumulation. These changes were attenuated, but not reversed, in cells overexpressing SPRY2. Phosphorylation of protein kinases across key signalling pathways (including Akt and mitogen activated protein kinases) was not altered after SPRY2 KO. Transcriptome profiling in SPRY2 KO and mock (control) cells revealed a number of differentially expressed genes related to cholesterol biosynthesis, cell cycle regulation and cellular signalling pathways. Phospholipase A2 group IIA (PLA2G2A) mRNA level was subsequently validated as significantly upregulated following SPRY2 KO, highlighting this as a potential mediator downstream of SPRY2. CONCLUSION: These findings suggest a role for SPRY2 in glucose and lipid metabolism in hepatocytes and contribute to clarifying the function of this gene in the context of metabolic diseases.

Detailed Functional Characterization of a Waist-Hip Ratio Locus in 7p15.2 Defines an Enhancer Controlling Adipocyte Differentiation.

We combined CAGE sequencing in human adipocytes during differentiation with data from genome-wide association studies to identify an enhancer in the SNX10 locus on chromosome 7, presumably involved in body fat distribution. Using reporter assays and CRISPR-Cas9 gene editing in human cell lines, we characterized the role of the enhancer in adipogenesis. The enhancer was active during adipogenesis and responded strongly to insulin and isoprenaline. The allele associated with increased waist-hip ratio in human genetic studies was associated with higher enhancer activity. Mutations of the enhancer resulted in less adipocyte differentiation. RNA sequencing of cells with disrupted enhancer showed reduced expression of established adipocyte markers, such as ADIPOQ and LPL, and identified CHI3L1 on chromosome 1 as a potential gene involved in adipocyte differentiation. In conclusion, we identified and characterized an enhancer in the SNX10 locus and outlined its plausible mechanisms of action and downstream targets.

Role of peroxisome proliferator-activated receptor gamma Pro12Ala polymorphism in human adipose tissue: assessment of adipogenesis and adipocyte glucose and lipid turnover.

The protective mechanisms of peroxisome proliferator-activated receptor gamma (PPARγ) Pro12Ala polymorphism in type 2 diabetes (T2D) are unclear. We obtained subcutaneous adipose tissue (AT) before and 3 h after oral glucose (OGTT) in carriers and non-carriers of the Ala allele (12 Pro/Pro, 15 Pro/Ala, and 13 Ala/Ala). Adipogenesis, adipocyte glucose uptake and lipolysis as well as PPARγ target gene expression were investigated and compared between the genotype groups. During fasting and post-OGTT, neither basal nor insulin-stimulated adipocyte glucose uptake differed between genotypes. Compared to fasting, a decreased hormone-sensitive lipase gene expression in Pro/Pro (p < 0.05) was accompanied with a higher antilipolytic effect of insulin post-OGTT (p < 0.01). The adipocyte size was similar across groups. Preadipocyte differentiation rates between Pro/Pro and Ala/Ala were unchanged. In conclusion, no major differences in AT differentiation, glucose uptake, lipolysis or expression of PPARγ target genes were observed between different PPARγ Pro12Ala genotypes. Albeit small, our study may suggest that other pathways in AT or effects exerted in other tissues might contribute to the Pro12Ala-mediated protection against T2D.

FKBP5 expression in human adipose tissue: potential role in glucose and lipid metabolism, adipogenesis and type 2 diabetes.

PURPOSE: Here, we explore the involvement of FKBP51 in glucocorticoid-induced insulin resistance (IR) in human subcutaneous adipose tissue (SAT), including its potential role in type 2 diabetes (T2D). Moreover, we assess the metabolic effects of reducing the activity of FKBP51 using the specific inhibitor SAFit1. METHODS: Human SAT was obtained by needle biopsies of the lower abdominal region. FKBP5 gene expression was assessed in fresh SAT explants from a cohort of 20 T2D subjects group-wise matched by gender, age and BMI to 20 non-diabetic subjects. In addition, human SAT was obtained from non-diabetic volunteers (20F/9M). SAT was incubated for 24 h with or without the synthetic glucocorticoid dexamethasone and SAFit1. Incubated SAT was used to measure the glucose uptake rate in isolated adipocytes. RESULTS: FKBP5 gene expression levels in SAT positively correlated with several indices of IR as well as glucose area under the curve during oral glucose tolerance test (r = 0.33, p < 0.05). FKBP5 gene expression levels tended to be higher in T2D subjects compared to non-diabetic subjects (p = 0.088). Moreover, FKBP5 gene expression levels were found to inversely correlate with lipolytic, lipogenic and adipogenic genes. SAFit1 partly prevented the inhibitory effects of dexamethasone on glucose uptake. CONCLUSIONS: FKBP5 gene expression in human SAT tends to be increased in T2D subjects and is related to elevated glucose levels. Moreover, FKBP5 gene expression is inversely associated with the expression of lipolytic, lipogenic and adipogenic genes. SAFit1 can partly prevent glucose uptake impairment by glucocorticoids, suggesting that FKBP51 might be a key factor in glucocorticoid-induced IR.

Glucose challenge metabolomics implicates medium-chain acylcarnitines in insulin resistance.

Insulin resistance (IR) predisposes to type 2 diabetes and cardiovascular disease but its causes are incompletely understood. Metabolic challenges like the oral glucose tolerance test (OGTT) can reveal pathogenic mechanisms. We aimed to discover associations of IR with metabolite trajectories during OGTT. In 470 non-diabetic men (age 70.6 ± 0.6 years), plasma samples obtained at 0, 30 and 120 minutes during an OGTT were analyzed by untargeted liquid chromatography-mass spectrometry metabolomics. IR was assessed with the hyperinsulinemic-euglycemic clamp method. We applied age-adjusted linear regression to identify metabolites whose concentration change was related to IR. Nine trajectories, including monounsaturated fatty acids, lysophosphatidylethanolamines and a bile acid, were significantly associated with IR, with the strongest associations observed for medium-chain acylcarnitines C10 and C12, and no associations with L-carnitine or C2-, C8-, C14- or C16-carnitine. Concentrations of C10- and C12-carnitine decreased during OGTT with a blunted decline in participants with worse insulin resistance. Associations persisted after adjustment for obesity, fasting insulin and fasting glucose. In mouse 3T3-L1 adipocytes exposed to different acylcarnitines, we observed blunted insulin-stimulated glucose uptake after treatment with C10- or C12-carnitine. In conclusion, our results identify medium-chain acylcarnitines as possible contributors to IR.

Drosophila exoribonuclease nibbler is a tumor suppressor, acts within the RNAi machinery and is not enriched in the nuage during early oogenesis.

BACKGROUND: micro RNAs (miRNAs) are important regulators of many biological pathways. A plethora of steps are required to form, from a precursor, the mature miRNA that eventually acts on its target RNA to repress its expression or to inhibit translation. Recently, Drosophila nibbler (nbr) has been shown to be an important player in the maturation process of miRNA and piRNA. Nbr is an exoribonuclease which helps to shape the 3' end of miRNAs by trimming the 3' overhang to a final length. RESULTS: In contrast to previous reports on the localization of Nbr, we report that 1) Nbr is expressed only during a short time of oogenesis and appears ubiquitously localized within oocytes, and that 2) Nbr was is not enriched in the nuage where it was shown to be involved in piwi-mediated mechanisms. To date, there is little information available on the function of nbr for cellular and developmental processes. Due to the fact that nbr mutants are viable with minor deleterious effects, we used the GAL4/UAS over-expression system to define novel functions of nbr. We disclose hitherto unknown functions of nbr 1) as a tumor suppressor and 2) as a suppressor of RNAi. Finally, we confirm that nbr is a suppressor of transposon activity. CONCLUSIONS: Our data suggest that nbr exerts much more widespread functions than previously reported from trimming 3' ends of miRNAs only.

BANK1 controls CpG-induced IL-6 secretion via a p38 and MNK1/2/eIF4E translation initiation pathway.

BANK1, an adaptor protein expressed in B cells, plays a little understood role in B cell signaling. Because BANK1 contains an N-terminal putative Toll/IL-1R receptor domain, we used mouse Bank1(-/-) splenic B cells to test whether BANK1 affects signaling induced by the TLR9 agonist CpG. Following CpG stimulation, BANK1 deficiency reduced p38 phosphorylation without affecting that of ERK or JNK and reduced IL-6 secretion. Bank1(-/-) B cells showed reduced phosphorylation of MNK1/2 and eIF4E, suggesting an effect on translation initiation, whereas Bank1(-/-) had no effect on IL-6 mRNA stability, thus suggesting that BANK1 has no effect on MK2 signaling. IL-6 secretion observed when CpG stimulation was combined with anti-CD40 was reduced in the absence of BANK1. Whereas in the presence of anti-CD40 stimulation CpG induced a stronger phosphorylation of AKT, mTOR, and 4E-BP1, Bank1(-/-) had no effect on phosphorylation of mTOR and 4E-BP1, and a weak effect on AKT, implying that BANK1 does not affect the release of eIF4E by phospho-4E-BP1. Taken together, these data establish a previously unrecognized role for BANK1 in CpG-induced responses by splenic B cells on p38 signaling and control of translation initiation of IL-6 via MNK1/2 and eIF4E.

BANK1 and BLK act through phospholipase C gamma 2 in B-cell signaling.

The B cell adaptor protein with ankyrin repeats (BANK1) and the B lymphoid tyrosine kinase (BLK) have been genetically associated with autoimmunity. The proteins of these genes interact physically and work in concert during B-cell signaling. Little is know about their interactions with other B-cell signaling molecules or their role in the process. Using yeast two hybrid (Y2H) we sought for factors that interact with BANK1. We found that the molecular switch PLCg2 interacts with BANK1 and that the interaction is promoted by B-cell receptor (BCR) stimulation. We found further that the kinase activity of BLK enhanced BANK1- PLCg2 binding and that the interaction was suppressed upon BLK depletion. Immunoprecipitation and mutational analysis demonstrated that the interaction between BANK1 and PLCg2 was dependent on specific tyrosine and proline residues on the adaptor protein. Our results provide new information important to understand the role of these two genes in basic B-cell physiology and immune-related diseases.

Fine mapping and conditional analysis identify a new mutation in the autoimmunity susceptibility gene BLK that leads to reduced half-life of the BLK protein.

OBJECTIVES: To perform fine mapping of the autoimmunity susceptibility gene BLK and identify functional variants involved in systemic lupus erythematosus (SLE). METHODS: Genotyping of 1163 European SLE patients and 1482 controls and imputation were performed covering the BLK gene with 158 single-nucleotide polymorphisms. Logistic regression analysis was done using PLINK and conditional analyses using GENABEL's test score. Transfections of BLK constructs on HEK293 cells containing the novel mutation or the wild type form were analysed for their effect on protein half-life using a protein stability assay, cycloheximide and western blot. CHiP-qPCR for detection of nuclear factor κ B (NFkB) binding. RESULTS: Fine mapping of BLK identified two independent genetic effects with functional consequences: one represented by two tightly linked associated haplotype blocks significantly enriched for NFκB-binding sites and numerous putative regulatory variants whose risk alleles correlated with low BLK mRNA levels. Binding of NFkBp50 and p65 to an associated 1.2 Kb haplotype segment was confirmed. A second independent genetic effect was represented by an Ala71Thr, low-frequency missense substitution with an OR=2.31 (95% CI 1.38 to 3.86). The 71Thr decreased BLK protein half-life. CONCLUSIONS: These results show that rare and common regulatory variants in BLK are involved in disease susceptibility and both, albeit independently, lead to reduced levels of BLK protein.

Genetic and physical interaction of the B-cell systemic lupus erythematosus-associated genes BANK1 and BLK.

OBJECTIVES: Altered signalling in B cells is a predominant feature of systemic lupus erythematosus (SLE). The genes BANK1 and BLK were recently described as associated with SLE. BANK1 codes for a B-cell-specific cytoplasmic protein involved in B-cell receptor signalling and BLK codes for an Src tyrosine kinase with important roles in B-cell development. To characterise the role of BANK1 and BLK in SLE, a genetic interaction analysis was performed hypothesising that genetic interactions could reveal functional pathways relevant to disease pathogenesis. METHODS: The GPAT16 method was used to analyse the gene-gene interactions of BANK1 and BLK. Confocal microscopy was used to investigate co-localisation, and immunoprecipitation was used to verify the physical interaction of BANK1 and BLK. RESULTS: Epistatic interactions between BANK1 and BLK polymorphisms associated with SLE were observed in a discovery set of 279 patients and 515 controls from northern Europe. A meta-analysis with 4399 European individuals confirmed the genetic interactions between BANK1 and BLK. As BANK1 was identified as a binding partner of the Src tyrosine kinase LYN, the possibility that BANK1 and BLK could also show a protein-protein interaction was tested. The co-immunoprecipitation and co-localisation of BLK and BANK1 were demonstrated. In a Daudi cell line and primary naive B cells endogenous binding was enhanced upon B-cell receptor stimulation using anti-IgM antibodies. CONCLUSION: This study shows a genetic interaction between BANK1 and BLK, and demonstrates that these molecules interact physically. The results have important consequences for the understanding of SLE and other autoimmune diseases and identify a potential new signalling pathway.

Recent findings on genetics of systemic autoimmune diseases.

Association studies of over 1 million SNPs capturing most of the human genome common variation became possible thanks to the information provided by the HapMap International project and the development of high-throughput genotyping technologies at accessible prices. Genome-wide scans analyzing thousands of individuals have now identified most if not all of the major genes involved in susceptibility for several systemic autoimmune diseases. In particular, results for rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and systemic sclerosis (SSc) are reviewed here. While most genes are shared between diseases, few seem to be unique reflecting that we still are long before knowing all genes, their interactions with other genes and the environment and their impact on biological functions.

Expression and regulation of Spätzle-processing enzyme in Drosophila.

The Drosophila melanogaster Toll receptor controls embryonic dorsal-ventral axis formation and is crucial for the innate immune response. In both cases, Toll is activated by the enzymatically cleaved form of its ligand Spätzle (Spz). During axis formation, Spz is cleaved by the maternally provided serine protease Easter while the Spätzle-processing enzyme (SPE) activates Spz after infection. We confirm the role of SPE in immunity and show that it is a zygotic gene specifically expressed in immune tissues implying that the dual activation of Spz is achieved by differential spatiotemporal expression of two similar but distinct serine proteases.