WHIM syndrome is a rare primary immunodeficiency disorder caused by gain-of-function mutations of the chemokine receptor CXCR4, leading to abnormal and exacerbated leukocyte trafficking. It is associated with severe neutropenia and lymphopenia, and recurrent infections. Few pediatric cases have been reported, but comprehensive analyses of the composition and function of peripheral lymphocyte populations in pediatric WHIM syndrome are lacking. Here we report the case of a 6-year-old male patient carrying a CXCR4 c.1000C>T gain-of-function mutation, presenting with characteristic manifestations such as abnormal orientation of the cerebellar folia, myelokathexis and severe neutropenia as well as lymphopenia. In-depth analysis of peripheral lymphocyte subpopulations revealed an elevated CD4/CD8 T-cell ratio while T-cell activation, expansion and cytokine production were normal. B lymphopenia was accompanied with a shift in circulating B-cell populations towards transitional stages, and increased apoptosis. Interestingly, despite normal serum immunoglobulin levels, vaccination responses and B-cell receptor dependent activation, the patient’s B cells showed a reduced capacity for plasmablast differentiation in vitro. These findings warrant follow-up studies in larger patient cohorts, as longitudinal monitoring of B-cell function might reveal emerging humoral defects in WHIM pediatric patients reaching adolescence and adulthood.

OBJECTIVES:The objectives of this study were to characterize some phenotypic and functional aspects of fibroblast-like synoviocytes isolated from the Synovial Fluid (SF-FLSs) of patients affected by Juvenile Idiopathic Arthritis (JIA) with active disease and to compare SF-FLS characteristics with those reported in the literature for FLSs of the SM (Synovial Membrane) in adult rheumatic patients. METHODS:FLSs were isolated from the SF of JIA patients with active disease by therapeutic arthrocentesis. SF-FLS surface marker expression was assessed by cytofluorimetry; proinflammatory cytokine and MMP gene expression was investigated by quantitative RT-PCR (qRT-PCR); and chondrogenic properties were evaluated by staining with Alcian-Blue. RESULTS:SF-FLSs display a CD45-,CD34-,CD90+,PDPN+ phenotype and exhibit a significant increase in the expression of genes coding for pro-inflammatory cytokines, but not MMPs, when treated with TNF-α, a cytokine present in the joint environment. In addition, SF-FLSs express the chondrogenic genes BMP4 and Aggrecan (AGG) and show the ability to differentiate towards a chondrocyte-like phenotype when cultured in TGF-β-enriched medium. CONCLUSION:FLSs from the SF of JIA patients display a phenotype that has pro-inflammatory, rather than tissue-disruptive, activity; this is similar to what is observed in cells from the sublining region of the SM in adult arthritis patients. In addition, they show chondrogenic ability, indicating the potential for SF-FLSs as an in vitro model for chondrocytes.

Introduction:Oligoarthritis, the most common form of Juvenile Idiopathic Arthritis in Western countries and a leading cause of disability, exhibits a variable clinical course. Early identification of children at risk of polyarticular extension is critical for guiding targeted therapy, but requires new biomarkers. This study aimed at profiling T cell and monocyte/macrophage (MM) subset composition and activation/maturation state combined with extracellular vesicle (EV) surface markers in synovial fluid (SF) and peripheral blood (PB) from new-onset Oligoarthritis patients to prospectively evaluate their correlation with clinical course over a two-year follow-up period and identify potential prognostic biomarkers. Methods:SF and PB samples were collected from 42 untreated patients at disease onset. Immune cell subsets were analyzed by flow cytometry, EV marker expression profiles by bead-based multiplex assays, and soluble TREM1 (sTREM1) levels by ELLA. Differences between patients exhibiting oligoarticular course (Group 1) or polyarticular extension (Group 2) over two years of follow-up were assessed. Results:Group 2 patients showed significantly higher CD3:CD14 ratio (AUC = 0.831,p<0.005) and HLA-DR+ CD4+ T cell percentages (64.8%vs52.5%,p=0.02) in SF compared to Group 1 patients. In PB, both HLA-DR+CD4+ and HLA-DR+CD8+ cells were significantly increased (AUC = 0.946,p<0.001) in Group 2. Group 2 patients also exhibited significantly higher proportions of effector memory (EM) CD4+ (AUC = 0.911, p<0.001) and CD8+ (AUC:0.929, p<0.001) subsets, along with lower proportions of naïve CD4+ (AUC = 0.929, p<0.001) and CD8+ (AUC = 0.893, p<0.001) subsets in the circulation, that was reflected in a significantly higher EM:naïve ratios for both CD4+ (AUC = 0.893,p<0.001) and CD8+ (AUC = 0.946;p<0.001) populations. TREM1+ CD14+ cell percentages in both SF and PB were significantly (p<0.05) lower (SF: 83.6%vs90.47%; PB:40.16%vs53.21%), while sTREM1 levels higher (SF: 8926vs5822 pg/ml; PB:298.8vs232 pg/ml), in Group 2 compared to Group 1. Finally, SF-derived EVs from Group 2 showed significantly reduced HLA-ABC (AUC = 0.857,p=0.012) and CD3 (AUC = 0.949,p<0.001) expression. Combining these markers further improved the discriminatory performance of the models (AUC = 1,p<0.001). Discussion:This exploratory study identifies novel immune classifiers combining T lymphocytes and MM subsets with EV markers which stratify, at onset, Oligoarthritis patients who will develop polyarticular extension and provide important mechanistic insights into arthritis progression.

Neuroblastoma (NB) is the most common extracranial solid tumor during infancy, causing up to 10% of mortality in children; thus, identifying novel early and accurate diagnostic and prognostic biomarkers is mandatory. NB-derived exosomes carry proteins (Exo-prots) reflecting the status of the tumor cell of origin. The purpose of this study was to characterize, for the first time, the Exo-prots specifically expressed in NB patients associated with tumor phenotype and disease stage. We isolated exosomes from plasma specimens of 24 HR-NB patients and 24 low-risk (LR-NB) patients at diagnosis and of 24 age-matched healthy controls (CTRL). Exo-prot expression was measured by liquid chromatography–mass spectrometry. The data are available via ProteomeXchange (PXD042422). The NB patients had a different Exo-prot expression profile compared to the CTRL. The deregulated Exo-prots in the NB specimens acted mainly in the tumor-associated pathways. The HR-NB patients showed a different Exo-prot expression profile compared to the LR-NB patients, with the modulation of proteins involved in cell migration, proliferation and metastasis. NCAM, NCL, LUM and VASP demonstrated a diagnostic value in discriminating the NB patients from the CTRL; meanwhile, MYH9, FN1, CALR, AKAP12 and LTBP1 were able to differentiate between the HR-NB and LR-NB patients with high accuracy. Therefore, Exo-prots contribute to NB tumor development and to the aggressive metastatic NB phenotype.

IntroductionNew early low-invasive biomarkers are demanded for the management of Oligoarticular Juvenile Idiopathic Arthritis (OJIA), the most common chronic pediatric rheumatic disease in Western countries and a leading cause of disability. A deeper understanding of the molecular basis of OJIA pathophysiology is essential for identifying new biomarkers for earlier disease diagnosis and patient stratification and to guide targeted therapeutic intervention. Proteomic profiling of extracellular vesicles (EVs) released in biological fluids has recently emerged as a minimally invasive approach to elucidate adult arthritis pathogenic mechanisms and identify new biomarkers. However, EV-prot expression and potential as biomarkers in OJIA have not been explored. This study represents the first detailed longitudinal characterization of the EV-proteome in OJIA patients. MethodsFourty-five OJIA patients were recruited at disease onset and followed up for 24 months, and protein expression profiling was carried out by liquid chromatography-tandem mass spectrometry in EVs isolated from plasma (PL) and synovial fluid (SF) samples. ResultsWe first compared the EV-proteome of SF vs paired PL and identified a panel of EV-prots whose expression was significantly deregulated in SF. Interaction network and GO enrichment analyses performed on deregulated EV-prots through STRING database and ShinyGO webserver revealed enrichment in processes related to cartilage/bone metabolism and inflammation, suggesting their role in OJIA pathogenesis and potential value as early molecular indicators of OJIA development. Comparative analysis of the EV-proteome in PL and SF from OJIA patients vs PL from age/gender-matched control children was then carried out. We detected altered expression of a panel of EV-prots able to differentiate new-onset OJIA patients from control children, potentially representing a disease-associated signature measurable at both the systemic and local levels with diagnostic potential. Deregulated EV-prots were significantly associated with biological processes related to innate immunity, antigen processing and presentation, and cytoskeleton organization. Finally, we ran WGCNA on the SF- and PL-derived EV-prot datasets and identified a few EV-prot modules associated with different clinical parameters stratifying OJIA patients in distinct subgroups. DiscussionThese data provide novel mechanistic insights into OJIA pathophysiology and an important contribution in the search of new candidate molecular biomarkers for the disease.

Juvenile Idiopathic Arthritis (JIA) represents the most common chronic pediatric arthritis in Western countries and a leading cause of disability in children. Despite recent clinical achievements, patient management is still hindered by a lack of diagnostic/prognostic biomarkers and targeted treatment protocols. MicroRNAs (miRNAs) are short non-coding RNAs playing a key role in gene regulation, and their involvement in many pathologies has been widely reported in the literature. In recent decades, miRNA's contribution to the regulation of the immune system and the pathogenesis of autoimmune diseases has been demonstrated. Furthermore, miRNAs isolated from patients' biological samples are currently under investigation for their potential as novel biomarkers. This review aims to provide an overview of the state of the art on miRNA investigation in JIA. The literature addressing the expression of miRNAs in different types of biological samples isolated from JIA patients was reviewed, focusing in particular on their potential application as diagnostic/prognostic biomarkers. The role of miRNAs in the regulation of immune responses in affected joints will also be discussed along with their potential utility as markers of patients' responses to therapeutic approaches. This information will be of value to investigators in the field of pediatric rheumatology, encouraging further research to increase our knowledge of miRNAs' potential for future clinical applications in JIA.

Dear Editor, Oligoarticular juvenile idiopathic arthritis (OJIA) is the most common chronic paediatric arthritis in Western countries and a major cause of childhood disability.1 Early diagnosis and prediction of disease course and therapeutic response are crucial for patient management but are hindered by the lack of biomarkers. Identification of new low-invasive biomarkers is thus highly required to improve the current diagnosis of OJIA patients and help with the setting up of targeted treatments at disease onset, which would allow to reduce the burden of the disease, limit the occurrence of joint damage and loss of functionality, minimize patient exposure to the potential side-effects of ineffective medication, and induce earlier remission, thus enhancing patient quality of life2 (Supporting Information, Section 1). Extracellular vesicles (EVs) released into biologic fluids have gained increased recognition as key mediators of the pathogenesis of many chronic inflammatory and autoimmune diseases, including adult arthritides,3 and as a reliable and enriched source of disease biomarkers, by virtue of their cargo of bioactive molecules (nucleic acids, proteins, and lipids) of cellular origin, which can be transferred to, and elicit responses in, recipient cells.4 Analysis of microRNAs encapsulated in EVs (EV-miRs) provides a powerful means for new noninvasive biomarker discovery, given their high stability, concentration, and integrity coupled to tissue specificity5 (Supporting Information, Section 1). Recent studies indicated the diagnostic/prognostic potential of dysregulated EV-miRs in adult rheumatic patients.6,7 However, EV-miR expression and potential as biomarkers in OJIA has not been investigated. The aimof this studywas to identify candidate EV-miR-based biomarkers in children with newly diagnosed OJIA. Because joints are the main targets of clinical manifestations in OJIA, we first optimized the protocol for profiling EV-miRs in small volumes of synovial fluid (SF) collected from arthritic joints. We then searched

Objective JIA is a chronic inflammatory disease of unknown origin. The regulation of inflammatory processes involves multiple cellular steps including mRNA transcription and translation. Different miRNAs control these processes tightly. We aimed to determine the roles of specific miRNAs within JIA pathogenesis. Methods We performed a global miRNA expression analysis in parallel in cells from the arthritic joint and peripheral blood of oligoarticular JIA patients and healthy controls. Quantitative RT-PCR analysis was used to verify expression of miRNA in T cells. Ex vivo experiments and flow cytometric analyses were used to analyse proliferation and redox metabolism. Results Global miRNA expression analysis demonstrated a different composition of miRNA expression at the site of inflammation compared with peripheral blood. Bioinformatic analysis of predicted miRNA target genes suggest a huge overrepresentation of genes involved in metabolic and oxidative stress pathways in the inflamed joint. Despite enhanced reactive oxygen species (ROS) levels within the local inflammatory milieu, JIA T cells are hyperproliferative and reveal an overexpression of miR-23a, which is an inhibitor of Peptidyl-prolyl isomerase F (PPIF), the regulator of mitochondrial ROS escape. Mitochondrial ROS escape is diminished in JIA T cells, resulting in their prolonged survival. Conclusion Our data suggest that miRNA-dependent mitochondrial ROS shuttling might be a mechanism that contributes to T cell regulation in JIA at the site of inflammation.

Glycogen Storage Disease type 1b (GSDIb) is a genetic disorder with long term severe complications. Accumulation of the glucose analog 1,5-anhydroglucitol-6-phosphate (1,5AG6P) in neutrophils inhibits the phosphorylation of glucose in these cells, causing neutropenia and neutrophil dysfunctions. This condition leads to serious infections and inflammatory bowel disease (IBD) in GSDIb patients. We show here that dapagliflozin, an inhibitor of the renal sodium-glucose co-transporter-2 (SGLT2), improves neutrophil function in an inducible mouse model of GSDIb by reducing 1,5AG6P accumulation in myeloid cells.

Fanconi Anemia (FA) is a disease characterized by bone marrow (BM) failure and aplastic anemia. In addition to a defective DNA repair system, other mechanisms are involved in its pathogenesis, such as defective mitochondrial metabolism, accumulation of lipids, and increment of oxidative stress production. To better understand the role of these metabolic alterations in the process of HSC maturation in FA, we evaluated several biochemical and cellular parameters on mononuclear cells isolated from the bone marrow of FA patients or healthy donors. To mimic the cellular residence in the BM niche or their exit from the BM niche to the bloodstream, cells have been grown in hypoxic or normoxic conditions, respectively. The data show that, in normoxic conditions, a switch from anaerobic to aerobic metabolism occurs both in healthy and in pathological samples. However, in FA cells this change is associated with altered oxidative phosphorylation, the increment of oxidative stress production, no activation of the endogenous antioxidant defenses and arrest in the G2M phase of the cell cycle. By contrast, FA cells grown in hypoxic conditions do not show cell cycle and metabolic alterations in comparison to the healthy control, maintaining both an anaerobic flux. The data reported herein suggests that the passage from the BM niche to the bloodstream represents a crucial point in the FA pathogenesis associated with mitochondrial dysfunction.

Background: Tetralogy of Fallot (ToF) and Atrial Septal Defects (ASD) are the most common types of congenital heart diseases and a major cause of childhood morbidity and mortality. Cardiopulmonary bypass (CPB) is used during corrective cardiac surgery to support circulation and heart stabilization. However, this procedure triggers systemic inflammatory and stress response and consequent increased risk of postoperative complications. The aim of this study was to define the molecular bases of ToF and ASD pathogenesis and response to CPB and identify new potential biomarkers. Methods: Comparative transcriptome analysis of right atrium specimens collected from 10 ToF and 10 ASD patients was conducted before (Pre-CPB) and after (Post-CPB) corrective surgery. Total RNA isolated from each sample was individually hybridized on Affymetrix HG-U133 Plus Array Strips containing 38,500 unique human genes. Differences in the gene expression profiles and functional enrichment/network analyses were assessed using bioinformatic tools. qRT-PCR analysis was used to validate gene modulation. Results: Pre-CPB samples showed significant differential expression of a total of 72 genes, 28 of which were overexpressed in ToF and 44 in ASD. According to Gene Ontology annotation, the mostly enriched biological processes were represented by matrix organization and cell adhesion in ToF and by muscle development and contractility in ASD specimens. GSEA highlighted the specific enrichment of hypoxia gene sets in ToF samples, pointing to a role for hypoxia in disease pathogenesis. The post-CPB myocardium exhibited significant alterations in the expression profile of genes related to transcription regulation, growth/apoptosis, inflammation, adhesion/matrix organization, and oxidative stress. Among them, only 70 were common to the two disease groups, whereas 110 and 24 were unique in ToF and ASD, respectively. Multiple functional interactions among differentially expressed gene products were predicted by network analysis. Interestingly, gene expression changes in ASD samples followed a consensus hypoxia profile. Conclusion: Our results provide a comprehensive view of gene reprogramming in right atrium tissues of ToF and ASD patients before and after CPB, defining specific molecular pathways underlying disease pathophysiology and myocardium response to CPB. These findings have potential translational value because they identify new candidate prognostic markers and targets for tailored cardioprotective post-surgical therapies.

Inflammatory cells are major players in the onset of cancer. The degree of inflammation and type of inflammatory cells in the tumor microenvironment (TME) are responsible for tilting the balance between tumor progression and regression. Cancer-related inflammation has also been shown to influence the efficacy of conventional therapy. Mononuclear phagocytes (MPs) represent a major component of the inflammatory circuit that promotes tumor progression. Despite their potential to activate immunosurveillance and exert anti-tumor responses, MPs are subverted by the tumor to support its growth, immune evasion, and spread. MP responses in the TME are dictated by a network of stimuli integrated through the cross-talk between activatory and inhibitory receptors. Alterations in receptor expression/signaling can create excessive inflammation and, when chronic, promote tumorigenesis. Research advances have led to the development of new therapeutic strategies aimed at receptor targeting to induce a tumor-infiltrating MP switch from a cancer-supportive toward an anti-tumor phenotype, demonstrating efficacy in different human cancers. This review provides an overview of the role of MP receptors in inflammation-mediated carcinogenesis and discusses the most recent updates regarding their targeting for immunotherapeutic purposes. We focus in particular on the TREM-1 receptor, a major amplifier of MP inflammatory responses, highlighting its relevance in the development and progression of several types of inflammation-associated malignancies and the promises of its inhibition for cancer immunotherapy.

Background In the last years miRNAs have emerged as critical regulators of innate and adaptive immune responses and an altered expression or function is associated with several inflammatory and autoimmune diseases. Therefore miRNAs are also believed to promote inflammatory processes within the inflamed joint of juvenile idiopathic arthritis (JIA) patients. It is furthermore known that oxidative stress is associated with JIA. Free radicals are implicated in joint damage and play an important role as secondary messengers in immunological responses. How and if miRNAs contribute to dysregulated reactive oxygen species (ROS) metabolism in JIA remains to be elucidated. Objectives We aimed to identify miRNAs and miRNA regulated pathways, which contribute to dysregulated immune cell responses within the inflamed joint. Methods: miRNA profiling was performed on peripheral blood mononuclear cells (PBMCs) from healthy children, PBMCS from 9 JIA patients and synovial fluid mononuclear cells (SFMCs) from the same JIA patients. Subsequently, GO and pathway enrichment analyses were performed on predicted target genes. Upregulation of miRNAs was confirmed in vitro after incubation with synovial fluid by qRT-PCR. Mitochondrial integrity, cellular ROS and Nrf2 protein expression were measured by flow cytometry. Results Transcriptome analysis of JIA SFMCs compared to HC PBMCs revealed strongly enhanced expression of miR23a and miR23a, miR27a, miR146a, and miR155, which are involved in oxidative stress responses. In addition, expression of those could be induced in healthy control PBMCs by synovial fluid ex vivo. ROS level in synovial fluid T cells were enhanced, while expression of Nrf2, the main regulator of anti-oxidative responses and a target of miR27a, remained low. Furthermore mitochondrial cyclophilin, which regulates ROS escape from mitochondria and is suppressed by miR23a, was downregulated in SFMCs as well. Conclusion SFMCs within the inflamed joint reveal a distinct miRNA expression profile. Especially miRNAs that are involved in regulation of ROS metabolism are upregulated. In line with this, expression of Nrf2 and mitochondrial cyclophilin which are important regulators of cellular ROS metabolism are reduced while production of ROS is enhanced. We suggest that higher abundance of miRNAs, that are involved in oxidative stress pathways, contribute to redox dysregulations within the inflamed joint and thereby contribute to inflammatory processes. Disclosure of Interests:  Kim Ohl: None declared, Patricia Klemm: None declared, Tobias Schwarz: None declared, federica Raggi: None declared, Alessandro Consolaro Grant/research support from: AbbVie, Pfizer, Joachim Peitz: None declared, Gerd Horneff: None declared, Klaus Tenbrock Grant/research support from: Pfizer, BMS, Novartis, Speakers bureau: Pfizer, Novartis

Despite intensive treatment, 50% of children with high-risk neuroblastoma (HR-NB) succumb to their disease. Progression through current trials evaluating the efficacy of new treatments for children with HR disease usually depends on an inadequate response to induction chemotherapy, assessed using imaging modalities. In this study, we sought to identify circulating biomarkers that might be detected in a simple blood sample to predict patient response to induction chemotherapy. Since exosomes released by tumor cells can drive tumor growth and chemoresistance, we tested the hypothesis that exosomal microRNA (exo-miRNAs) in blood might predict response to induction chemotherapy. The exo-miRNAs expression profile in plasma samples collected from children treated in HR-NBL-1/SIOPEN before and after induction chemotherapy was compared to identify a three exo-miRs signature that could discriminate between poor and good responders. Exo-miRNAs expression also provided a chemoresistance index predicting the good or poor prognosis of HR-NB patients.

Glycogen storage disease type 1a (GSD-1a) is a rare genetic disease caused by mutations in the catalytic subunit of the enzyme glucose-6-phosphatase-alpha (G6Pase-α). The majority of patients develop long-term complications including renal failure and hepatocellular adenoma/carcinoma. The purpose of this study was to ascertain the proteomic changes in the liver of LS-G6pc-/- mice, a murine model of GSD-1a, in comparison with wild type mice to identify potential biomarkers of the pathophysiology of the affected liver. We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to analyze liver lysates from a total of 20 LS-G6pc-/- and 18 wild type (WT) mice. We compared the proteomic expression profile of LS-G6pc-/- and WT mice. We identified 4138 significantly expressed proteins 1243 of which were differentially represented. Network and pathway analyses indicate that LS-G6pc-/- livers display an age-dependent modulation of the expression of proteins involved in specific biological processes associated with increased progression of liver disease. Moreover, we found upregulation of proteins involved in the process of tissue inflammation and macrophage polarization toward the M2 phenotype in LS-G6pc-/- mice with adenomas. Our results identify a metabolic reprogramming of glucose-6-P and a pathologic environment in the liver compatible with tumor development and progression.

Hypoxia, which characterizes most tumor tissues, can alter the function of different immune cell types, favoring tumor escape mechanisms. In this study, we show that hypoxia profoundly acts on NK cells by influencing their transcriptome, affecting their immunoregulatory functions, and changing the chemotactic responses of different NK cell subsets. Exposure of human peripheral blood NK cells to hypoxia for 16 or 96 h caused significant changes in the expression of 729 or 1,100 genes, respectively. Gene Set Enrichment Analysis demonstrated that these changes followed a consensus hypoxia transcriptional profile. As assessed by Gene Ontology annotation, hypoxia-targeted genes were implicated in several biological processes: metabolism, cell cycle, differentiation, apoptosis, cell stress, and cytoskeleton organization. The hypoxic transcriptome also showed changes in genes with immunological relevance including those coding for proinflammatory cytokines, chemokines, and chemokine-receptors. Quantitative RT-PCR analysis confirmed the modulation of several immune-related genes, prompting further immunophenotypic and functional studies. Multiplex ELISA demonstrated that hypoxia could variably reduce NK cell ability to release IFNγ, TNFα, GM-CSF, CCL3, and CCL5 following PMA+Ionomycin or IL15+IL18 stimulation, while it poorly affected the response to IL12+IL18. Cytofluorimetric analysis showed that hypoxia could influence NK chemokine receptor pattern by sustaining the expression of CCR7 and CXCR4. Remarkably, this effect occurred selectively (CCR7) or preferentially (CXCR4) on CD56bright NK cells, which indeed showed higher chemotaxis to CCL19, CCL21, or CXCL12. Collectively, our data suggest that the hypoxic environment may profoundly influence the nature of the NK cell infiltrate and its effects on immune-mediated responses within tumor tissues.

BACKGROUND AND AIMS:Glycogen storage disease type Ib (GSD1b) is a rare metabolic and immune disorder caused by a deficiency in the glucose-6-phosphate transporter (G6PT) and characterized by impaired glucose homeostasis, myeloid dysfunction, and long-term risk of hepatocellular adenomas. Despite maximal therapy, based on a strict diet and on granulocyte colony-stimulating factor treatment, long-term severe complications still develop. Understanding the pathophysiology of GSD1b is a prerequisite to develop new therapeutic strategies and depends on the availability of animal models. The G6PT-KO mouse mimics the human disease but is very fragile and rarely survives weaning. We generated a conditional G6PT-deficient mouse as an alternative model for studying the long-term pathophysiology of the disease. We utilized this conditional mouse to develop an inducible G6PT-KO model to allow temporally regulated G6PT deletion by the administration of tamoxifen (TM).METHODS:We generated a conditional G6PT-deficient mouse utilizing the CRElox strategy. Histology, histochemistry, and phenotype analyses were performed at different times after TM-induced G6PT inactivation. Neutrophils and monocytes were isolated and analyzed for functional activity with standard techniques.RESULTS:The G6PT-inducible KO mice display the expected disturbances of G6P metabolism and myeloid dysfunctions of the human disorder, even though with a milder intensity.CONCLUSIONS:TM-induced inactivation of G6PT in these mice leads to a phenotype which mimics that of human GSD1b patients. The conditional mice we have generated represent an excellent tool to study the tissue-specific role of the G6PT gene and the mechanism of long-term complications in GSD1b.