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Immunological tolerance removes or inactivates self-reactive B cells,including those that also recognize cross-reactive foreign antigens. Whereas a few microbial pathogens exploit these holes" in the B cell repertoire by mimicking host antigens to evade immune surveillance the extent to which tolerance reduces the B cell repertoire to foreign antigens is unknown. Here we use single-cell cultures to determine the repertoires of human B cell antigen receptors (BCRs) before (transitional B cells) and after (mature B cells) the second B cell tolerance checkpoint in both healthy donors and in patients with systemic lupus erythematosus (SLE) . In healthy donors the majority ({\~{}}70{\%}) of transitional B cells that recognize foreign antigens also bind human self-antigens (foreign+self) and peripheral tolerance halves the frequency of foreign+self-reactive mature B cells. In contrast in SLE patients who are defective in the second tolerance checkpoint frequencies of foreign+self-reactive B cells remain unchanged during maturation of transitional to mature B cells. Patterns of foreign+self-reactivity among mature B cells from healthy donors differ from those of SLE patients. We propose that immune tolerance significantly reduces the scope of the BCR repertoire to microbial pathogens and that cross-reactivity between foreign and self epitopes may be more common than previously appreciated." View Publication

We have recently demonstrated the formation of interconnecting canalicular cell processes in bone cells upon contact with basement membrane components. Here we have determined whether growth factors in the reconstituted basement membrane (Matrigel) were active in influencing the cellular network formation. Various growth factors including transforming growth factor beta (TGF-beta),epidermal growth factor (EGF),insulin-like growth factor 1,bovine fibroblast growth factor (bFGF),and platelet-derived growth factor (PDGF) were identified in Matrigel. Exogenous TGF-beta blocked the cellular network formation. Conversely,addition of TGF-beta 1 neutralizing antibodies to Matrigel stimulated the cellular network formation. bFGF,EGF,and PDGF all promoted cellular migration and organization on Matrigel. Addition of bFGF to MC3T3-E1 cells grown on Matrigel overcame the inhibitory effect of TGF-beta. Some TGF-beta remained bound to type IV collagen purified from the Engelbreth-Holm-Swarm tumor matrix. These data demonstrate that reconstituted basement membrane contains growth factors which influence cellular behavior,suggesting caution in the interpretation of experiments on cellular activity related to Matrigel,collagen type IV,and possibly other extracellular matrix components. View Publication

Accurate characterization of hematopoietic stem cells (HSC) products is needed to better anticipate the hematopoietic reconstitution and the outcome in patients. Although CD34+ viable cells enumeration is a key predictor of time to correction of aplasia,it does not fully inform about functionality of cells contained in the graft. CFU assay is the gold standard in vitro potency assay to assess clonogenicity of HSC and consists on the count and identification of colonies several days after culture in a semi solid media. Manual count of colonies with optic microscope is the most commonly used method but its important variability and subjectivity hinders the universal implementation of this potency assay. The aim of this study is to validate a standardized method using the STEMvision™ system,the first semi-automated instrument for imaging and scoring hematopoietic colonies,according to French and European recommendations. Results obtained highlight better performance criteria with STEMvision™ system than the manual method. This semi-automatic device tends to reduce the coefficients of variation of repeatability,inter-operator variability and intermediate precision. This newly available platform could represent an interesting option,significantly improving performances of CFU assays used for the characterization of hematopoietic progenitors. View Publication

It has been recently shown that increased oxidative phosphorylation,as reflected by increased mitochondrial activity,together with impairment of the mitochondrial stress response,can severely compromise hematopoietic stem cell (HSC) regeneration. Here we show that the NAD+-boosting agent nicotinamide riboside (NR) reduces mitochondrial activity within HSCs through increased mitochondrial clearance,leading to increased asymmetric HSC divisions. NR dietary supplementation results in a significantly enlarged pool of progenitors,without concurrent HSC exhaustion,improves survival by 80{\%},and accelerates blood recovery after murine lethal irradiation and limiting-HSC transplantation. In immune-deficient mice,NR increased the production of human leucocytes from hCD34+ progenitors. Our work demonstrates for the first time a positive effect of NAD+-boosting strategies on the most primitive blood stem cells,establishing a link between HSC mitochondrial stress,mitophagy,and stem-cell fate decision,and unveiling the potential of NR to improve recovery of patients suffering from hematological failure including post chemo- and radiotherapy. View Publication

In systemic lupus erythematosus,defective clearance of apoptotic debris and activation of innate cells result in a chronically activated type 1 IFN response,which can be measured in PBMCs of most patients. Metformin,a widely used prescription drug for Type 2 diabetes,has a therapeutic effect in several mouse models of lupus through mechanisms involving inhibition of oxidative phosphorylation and a decrease in CD4+ T cell activation. In this study,we report that in CD4+ T cells from human healthy controls and human systemic lupus erythematosus patients,metformin inhibits the transcription of IFN-stimulated genes (ISGs) after IFN-alpha treatment. Accordingly,metformin inhibited the phosphorylation of pSTAT1 (Y701) and its binding to IFN-stimulated response elements that control ISG expression. These effects were independent of AMPK activation or mTORC1 inhibition but were replicated using inhibitors of the electron transport chain respiratory complexes I,III,and IV. This indicates that mitochondrial respiration is required for ISG expression in CD4+ T cells and provides a novel mechanism by which metformin may exert a therapeutic effect in autoimmune diseases. View Publication

RNA polymerase III (Pol III) is an essential 17-subunit complex responsible for the transcription of small housekeeping RNAs such as transfer RNAs and 5S ribosomal RNA. Biallelic variants in four genes (POLR3A,POLR3B,and POLR1C and POLR3K) encoding Pol III subunits have previously been found in individuals with (neuro-) developmental disorders. In this report,we describe three individuals with biallelic variants in POLR3GL,a gene encoding a Pol III subunit that has not been associated with disease before. Using whole exome sequencing in a monozygotic twin and an unrelated individual,we detected homozygous and compound heterozygous POLR3GL splice acceptor site variants. RNA sequencing confirmed the loss of full-length POLR3GL RNA transcripts in blood samples of the individuals. The phenotypes of the described individuals are mainly characterized by axial endosteal hyperostosis,oligodontia,short stature,and mild facial dysmorphisms. These features largely fit within the spectrum of phenotypes caused by previously described biallelic variants in POLR3A,POLR3B,POLR1C,and POLR3K. These findings further expand the spectrum of POLR3-related disorders and implicate that POLR3GL should be included in genetic testing if such disorders are suspected. View Publication

Lupus glomerulonephritis (GN) is an autoimmune disease characterized by immune complex-deposition,complement activation and glomerular inflammation. In lupus-prone NZM2328 mice,the occurrence of lupus GN was accompanied by a decrease in Treg cells and an increase in proinflammatory cytokine-producing T cells. Because IL-33 in addition to IL-2 has been shown to be important for Treg cell proliferation and ST2 (IL-33 receptor) positive Treg cells are more potent in suppressor activity,a hybrid cytokine with active domains of IL-2 and IL-33 was generated to target the ST2+ Treg cells as a therapeutic agent to treat lupus GN. Three mouse models were used: spontaneous and Ad-IFNalpha- accelerated lupus GN in NZM2328 and the lymphoproliferative autoimmune GN in MRL/lpr mice. Daily injections of IL233 for 5 days prevented Ad-IFNalpha-induced lupus GN and induced remission of spontaneous lupus GN. The remission was permanent in that no relapses were detected. The remission was accompanied by persistent elevation of Treg cells in the renal lymph nodes. IL233 is more potent than IL-2 and IL-33 either singly or in combination in the treatment of lupus GN. The results of this study support the thesis that IL233 should be considered as a novel agent for treating lupus GN. View Publication

Ex vivo CRISPR gene editing in haematopoietic stem and progenitor cells has opened potential treatment modalities for numerous diseases. The current process uses electroporation,sometimes followed by virus transduction. While this complex manipulation has resulted in high levels of gene editing at some genetic loci,cellular toxicity was observed. We have developed a CRISPR nanoformulation based on colloidal gold nanoparticles with a unique loading design capable of cellular entry without the need for electroporation or viruses. This highly monodispersed nanoformulation avoids lysosomal entrapment and localizes to the nucleus in primary human blood progenitors without toxicity. Nanoformulation-mediated gene editing is efficient and sustained with different CRISPR nucleases at multiple loci of therapeutic interest. The engraftment kinetics of nanoformulation-treated primary cells in humanized mice are better relative to those of non-treated cells,with no differences in differentiation. Here we demonstrate non-toxic delivery of the entire CRISPR payload into primary human blood progenitors. View Publication

Precise gene editing in hematopoietic stem and progenitor cells (HSPCs) holds promise for treating genetic diseases. However,responses triggered by programmable nucleases in HSPCs are poorly characterized and may negatively impact HSPC engraftment and long-term repopulation capacity. Here,we induced either one or several DNA double-stranded breaks (DSBs) with optimized zinc-finger and CRISPR/Cas9 nucleases and monitored DNA damage response (DDR) foci induction,cell-cycle progression,and transcriptional responses in HSPC subpopulations,with up to single-cell resolution. p53-mediated DDR pathway activation was the predominant response to even single-nuclease-induced DSBs across all HSPC subtypes analyzed. Excess DSB load and/or adeno-associated virus (AAV)-mediated delivery of DNA repair templates induced cumulative p53 pathway activation,constraining proliferation,yield,and engraftment of edited HSPCs. However,functional impairment was reversible when DDR burden was low and could be overcome by transient p53 inhibition. These findings provide molecular and functional evidence for feasible and seamless gene editing in HSPCs. View Publication

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an arrhythmia syndrome characterized by adrenaline induced ventricular tachycardia. The primary genetic aetiologies underlying CPVT are either autosomal dominant or autosomal recessive inheritance,resulting from heterozygous mutations in cardiac ryanodine receptor (RYR2) and homozygous mutations in cardiac calsequestrin-2 (CASQ2),respectively. Recently,a large family with autosomal dominant CPVT due to a heterozygous mutation in CASQ2,p.Lys180Arg,was reported. This resource is the first induced pluripotent stem cell line generated from a patient with autosomal dominant CPVT due to a heterozygous mutation in CASQ2. Induced pluripotent stem cells were generated from the whole blood of a 40-year-old woman with severe CPVT who is heterozygous for the p.Lys180Arg CASQ2 mutation. Induced pluripotent stem cell (iPSC) characterization confirmed expression of pluripotency makers,trilineage differentiation potential,and the absence of exogenous pluripotency vector expression. View Publication

Patient-derived pancreatic ductal adenocarcinoma (PDAC) organoid systems show great promise for understanding the biological underpinnings of disease and advancing therapeutic precision medicine. Despite the increased use of organoids,the fidelity of molecular features,genetic heterogeneity,and drug response to the tumor of origin remain important unanswered questions limiting their utility. To address this gap in knowledge,primary tumor- and patient-derived xenograft (PDX)-derived organoids,and 2D cultures for in-depth genomic and histopathologic comparisons with the primary tumor were created. Histopathologic features and PDAC representative protein markers (e.g.,claudin 4 and CA19-9) showed strong concordance. DNA- and RNA-sequencing (RNAseq) of single organoids revealed patient-specific genomic and transcriptomic consistency. Single-cell RNAseq demonstrated that organoids are primarily a clonal population. In drug response assays,organoids displayed patient-specific sensitivities. In addition,the in vivo PDX response to FOLFIRINOX and gemcitabine/abraxane treatments were examined,which was recapitulated in vitro with organoids. This study has demonstrated that organoids are potentially invaluable for precision medicine as well as preclinical drug treatment studies because they maintain distinct patient phenotypes and respond differently to drug combinations and dosage. IMPLICATIONS: The patient-specific molecular and histopathologic fidelity of organoids indicate that they can be used to understand the etiology of the patient's tumor and the differential response to therapies and suggests utility for predicting drug responses. View Publication

CD4+ T cells recognize antigens through their T cell receptors (TCRs); however,additional signals involving costimulatory receptors,for example,CD28,are required for proper T cell activation. Alternative costimulatory receptors have been proposed,including members of the Toll-like receptor (TLR) family,such as TLR5 and TLR2. To understand the molecular mechanism underlying a potential costimulatory role for TLR5,we generated detailed molecular maps and logical models for the TCR and TLR5 signaling pathways and a merged model for cross-interactions between the two pathways. Furthermore,we validated the resulting model by analyzing how T cells responded to the activation of these pathways alone or in combination,in terms of the activation of the transcriptional regulators CREB,AP-1 (c-Jun),and NF-kappaB (p65). Our merged model accurately predicted the experimental results,showing that the activation of TLR5 can play a similar role to that of CD28 activation with respect to AP-1,CREB,and NF-kappaB activation,thereby providing insights regarding the cross-regulation of these pathways in CD4+ T cells. View Publication