Autoimmune amelogenesis imperfecta in patients with APS-1 and coeliac disease.

Ameloblasts are specialized epithelial cells in the jaw that have an indispensable role in tooth enamel formation-amelogenesis1. Amelogenesis depends on multiple ameloblast-derived proteins that function as a scaffold for hydroxyapatite crystals. The loss of function of ameloblast-derived proteins results in a group of rare congenital disorders called amelogenesis imperfecta2. Defects in enamel formation are also found in patients with autoimmune polyglandular syndrome type-1 (APS-1), caused by AIRE deficiency3,4, and in patients diagnosed with coeliac disease5-7. However, the underlying mechanisms remain unclear. Here we show that the vast majority of patients with APS-1 and coeliac disease develop autoantibodies (mostly of the IgA isotype) against ameloblast-specific proteins, the expression of which is induced by AIRE in the thymus. This in turn results in a breakdown of central tolerance, and subsequent generation of corresponding autoantibodies that interfere with enamel formation. However, in coeliac disease, the generation of such autoantibodies seems to be driven by a breakdown of peripheral tolerance to intestinal antigens that are also expressed in enamel tissue. Both conditions are examples of a previously unidentified type of IgA-dependent autoimmune disorder that we collectively name autoimmune amelogenesis imperfecta.

Clinical Features and Natural History of Paediatric Patients with Ulcerative Proctitis: A Multicentre Study from the Paediatric IBD Porto Group of ESPGHAN.

BACKGROUND AND AIMS: Ulcerative proctitis [UP] is an uncommon presentation in paediatric patients with ulcerative colitis. We aimed to characterize the clinical features and natural history of UP in children, and to identify predictors of poor outcomes. METHODS: This was a retrospective study involving 37 sites affiliated with the IBD Porto Group of ESPGHAN. Data were collected from patients aged <18 years diagnosed with UP between January 1, 2016 and December 31, 2020. RESULTS: We identified 196 patients with UP (median age at diagnosis 14.6 years [interquartile range, IQR 12.5-16.0]), with a median follow-up of 2.7 years [IQR 1.7-3.8]. The most common presenting symptoms were bloody stools [95%], abdominal pain [61%] and diarrhoea [47%]. At diagnosis, the median paediatric ulcerative colitis activity index [PUCAI] score was 25 [IQR 20-35], but most patients exhibited moderate-severe endoscopic inflammation. By the end of induction, 5-aminosalicylic acid administration orally, topically or both resulted in clinical remission rates of 48%, 48%, and 73%, respectively. The rates of treatment escalation to biologics at 1, 3, and 5 years were 10%, 22%, and 43%, respectively. In multivariate analysis, the PUCAI score at diagnosis was significantly associated with initiation of systemic steroids, or biologics, and subsequent acute severe colitis events and inflammatory bowel disease-associated admission, with a score ≥35 providing an increased risk for poor outcomes. By the end of follow-up, 3.1% of patients underwent colectomy. Patients with UP that experienced proximal disease progression during follow-up [48%] had significantly higher rates of a caecal patch at diagnosis and higher PUCAI score by the end of induction, compared to those without progression. CONCLUSION: Paediatric patients with UP exhibit high rates of treatment escalation and proximal disease extension.

Comparison of Clinical Outcomes in Pediatric Patients with Ileocolonic Crohn Disease Treated with Infliximab Versus Adalimumab.

OBJECTIVES: Infliximab is considered superior to adalimumab in patients with ulcerative colitis, especially in severe cases. Whether this is true for Crohn disease (CD) patients with colonic involvement is unclear. Our aim was to compare the clinical effectiveness of infliximab versus adalimumab in pediatric ileocolonic (L3) CD. METHODS: This retrospective study included patients <18 years with ileocolonic CD treated with infliximab or adalimumab between 2014 and 2021. Primary outcome was steroid-free clinical remission by week 52. Secondary outcomes were treatment modifications, drug discontinuation, inflammatory bowel disease (IBD)-associated hospitalizations, and surgery during the first year of treatment. RESULTS: We identified 74 patients treated with adalimumab and 41 with infliximab, with comparable demographic features. Concomitant immunomodulator therapy at biologic initiation was significantly lower in the adalimumab group (28% vs 85%, P < 0.001). Rates of drug intensification were higher in the infliximab group at end of induction (EOI) and at 52 weeks (55% vs 32% and 88% vs 46%, P < 0.001). Given significant differences between initial median Pediatric Crohn Disease Activity Index scores (20.0 [interquartile range, IQR 15.0-27.5] vs 11.0 [IQR 7.5-20.0] for infliximab and adalimumab groups, respectively, P < 0.001), propensity score matching was performed. Following matching, the rate of patients in steroid-free clinical remission by EOI was significantly higher in the adalimumab group (93.8% vs 46.9%, P < 0.001), but comparable by 1 year. Moreover, inflammatory markers and fecal calprotectin values were also similar at these time points. Rates of drug discontinuation, IBD-associated admissions, and surgery were similar between groups. CONCLUSIONS: In a retrospective study of patients with ileocolonic CD, adalimumab and infliximab had comparable outcomes by 52 weeks.

RIPK1 mutations causing infantile-onset IBD with inflammatory and fistulizing features.

Purpose: Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is an important regulator of necroptosis and inflammatory responses. We present the clinical features, genetic analysis and immune work-up of two patients with infantile-onset inflammatory bowel disease (IBD) resulting from RIPK1 mutations. Methods: Whole exome and Sanger sequencing was performed in two IBD patients. Mass cytometry time of flight (CyTOF) was conducted for in-depth immunophenotyping on one of the patient's peripheral blood mononuclear cells, and compared to control subjects and patients with Crohn's disease. Results: The patients presented with severe colitis and perianal fistulas in the first months of life, without severe/atypical infections. Genetic studies identified pathogenic genetic variants in RIPK1 (Patient 1, A c.1934C>T missense mutation in Exon 11; Patient 2, c.580G>A missense mutation residing in Exon 4). Protein modeling demonstrated that the mutation in Patient 1 displaces a water molecule, potentially disrupting the local environment, and the mutation in Patient 2 may lead to disruption of the packing and conformation of the kinase domain. Immunofluorescence RIPK1 staining in rectal biopsies demonstrated no expression for Patient 1 and minimal expression for Patient 2, compared to controls and patients with active Crohn's disease. Using CyTOF unbiased clustering analysis, we identified peripheral immune dysregulation in one of these patients, characterized by an increase in IFNγ CD8+ T cells along with a decrease in monocytes, dendritic cells and B cells. Moreover, RIPK1-deficient patient's immune cells exhibited decreased IL-6 production in response to lipopolysaccharide (LPS) across multiple cell types including T cells, B cells and innate immune cells. Conclusions: Mutations in RIPK1 should be considered in very young patients presenting with colitis and perianal fistulas. Given RIPK1's role in inflammasome activation, but also in epithelial cells, it is unclear whether IL1 blockade or allogeneic hematopoietic stem cell transplantation can suppress or cure the hyper-inflammatory response in these patients. Additional studies in humans are required to better define the role of RIPK1 in regulating intestinal immune responses, and how treatment can be optimized for patients with RIPK1 deficiency.

Early post-liver transplant thrombocytopenia in children: Clinical characteristics and significance.

BACKGROUND: Post-liver transplant thrombocytopenia is common and associated with worse outcome in adults. In children, however, the prevalence, course, and significance of post-liver transplantation thrombocytopenia are not described. Therefore, we aimed to assess this phenomenon in children. METHODS: A retrospective chart review of children who underwent liver transplantation at a single tertiary center between 2004 and 2021. RESULTS: Overall, 130 pediatric liver transplantations were reviewed. During the first 28 POD, thrombocytopenia was evident in 116 (89%, 95% CI 83%-94%). The median nadir platelet count was 54 K/µl (IQR: 37-99). Nadir platelet count was reached in half the patients by the third POD (IQR: 1-6). In multivariate analysis, preoperative platelet count (p = .024), volume of intraoperative packed cell transfusion (p = .045), and hypersplenism (p = .007) were associated with lower postoperative platelet counts. Patients with platelet count lower than the 50th centile on the first POD suffered from a more complicated course leading to a longer PICU admission (p = .039). CONCLUSIONS: Early post-liver transplant thrombocytopenia appears to be common in children and associated with preoperative thrombocytopenia, hypersplenism, and higher intraoperative blood transfusion volumes. A low first POD platelet count (<86 K/µl) was found to be independently associated with a more complicated postoperative course, suggesting the need for heightened surveillance.

An instructive role for Interleukin-7 receptor α in the development of human B-cell precursor leukemia.

Kinase signaling fuels growth of B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Yet its role in leukemia initiation is unclear and has not been shown in primary human hematopoietic cells. We previously described activating mutations in interleukin-7 receptor alpha (IL7RA) in poor-prognosis "ph-like" BCP-ALL. Here we show that expression of activated mutant IL7RA in human CD34+ hematopoietic stem and progenitor cells induces a preleukemic state in transplanted immunodeficient NOD/LtSz-scid IL2Rγnull mice, characterized by persistence of self-renewing Pro-B cells with non-productive V(D)J gene rearrangements. Preleukemic CD34+CD10highCD19+ cells evolve into BCP-ALL with spontaneously acquired Cyclin Dependent Kinase Inhibitor 2 A (CDKN2A) deletions, as commonly observed in primary human BCP-ALL. CRISPR mediated gene silencing of CDKN2A in primary human CD34+ cells transduced with activated IL7RA results in robust development of BCP-ALLs in-vivo. Thus, we demonstrate that constitutive activation of IL7RA can initiate preleukemia in primary human hematopoietic progenitors and cooperates with CDKN2A silencing in progression into BCP-ALL.

Targeting oncogenic interleukin-7 receptor signalling with N-acetylcysteine in T cell acute lymphoblastic leukaemia.

Activating mutations of the interleukin-7 receptor (IL7R) occur in approximately 10% of patients with T cell acute lymphoblastic leukaemia (T-ALL). Most mutations generate a cysteine at the transmembrane domain leading to receptor homodimerization through disulfide bond formation and ligand-independent activation of STAT5. We hypothesized that the reducing agent N-acetylcysteine (NAC), a well-tolerated drug used widely in clinical practice to treat acetaminophen overdose, would reduce disulfide bond formation, and inhibit mutant IL7R-mediated oncogenic signalling. We found that treatment with NAC disrupted IL7R homodimerization in IL7R-mutant DND-41 cells as assessed by non-reducing Western blot, as well as in a luciferase complementation assay. NAC led to STAT5 dephosphorylation and cell apoptosis at clinically achievable concentrations in DND-41 cells, and Ba/F3 cells transformed by an IL7R-mutant construct containing a cysteine insertion. The apoptotic effects of NAC could be rescued in part by a constitutively active allele of STAT5. Despite using doses lower than those tolerated in humans, NAC treatment significantly inhibited the progression of human DND-41 cells engrafted in immunodeficient mice. Thus, targeting leukaemogenic IL7R homodimerization with NAC offers a potentially effective and feasible therapeutic strategy that warrants testing in patients with T-ALL.

Novel activating mutations lacking cysteine in type I cytokine receptors in acute lymphoblastic leukemia.

Gain-of-function somatic mutations introducing cysteines to either the extracellular or to the transmembrane domain (TMD) in interleukin-7 receptor α (IL7R) or cytokine receptor-like factor 2 (CRLF2) have been described in acute lymphoblastic leukemias. Here we report noncysteine in-frame mutations in IL7R and CRLF2 located in a region of the TMD closer to the cytosolic domain. Biochemical and functional assays showed that these are activating mutations conferring cytokine-independent growth of progenitor lymphoid cells in vitro and are transforming in vivo. Protein fragment complementation assays suggest that despite the absence of cysteines, the mechanism of activation is through ligand-independent dimerization. Mutagenesis experiments and ConSurf calculations suggest that the mutations stabilize the homodimeric conformation, positioning the cytosolic kinases in predefined orientation to each other, thereby inducing spontaneous receptor activation independently of external signals. Hence, type I cytokine receptors may be activated in leukemia through 2 types of transmembrane somatic dimerizing mutations.

Towards precision medicine in childhood leukemia--insights from mutationally activated cytokine receptor pathways in acute lymphoblastic leukemia.

The successful therapy of childhood leukemia has been characterized by careful personalized adaptation of therapy by risk stratification. Yet almost all drugs are relatively non-specific. To achieve greater precision in therapy, druggable targets and specific targeting drugs are necessary. Here we review the recent discoveries of cytokine receptors and their signaling components in high risk leukemias and the potential approaches to target them.

Interleukin 7 and thymic stromal lymphopoietin: from immunity to leukemia.

Cancer is often caused by deregulation of normal developmental processes. Here, we review recent research on the aberrant activation of two hematopoietic cytokine receptors in acute lymphoid leukemias. Somatic events in the genes for thymic stromal lymphopoietin and Interleukin 7 receptors as well as in their downstream JAK kinases result in constitutive ligand-independent activation of survival and proliferation in B and T lymphoid precursors. Drugs targeting these receptors or the signaling pathways might provide effective therapies of these leukemias.

Gain-of-function mutations in interleukin-7 receptor-α (IL7R) in childhood acute lymphoblastic leukemias.

Interleukin-7 receptor α (IL7R) is required for normal lymphoid development. Loss-of-function mutations in this gene cause autosomal recessive severe combined immune deficiency. Here, we describe somatic gain-of-function mutations in IL7R in pediatric B and T acute lymphoblastic leukemias. The mutations cause either a serine-to-cysteine substitution at amino acid 185 in the extracellular domain (4 patients) or in-frame insertions and deletions in the transmembrane domain (35 patients). In B cell precursor leukemias, the mutations were associated with the aberrant expression of cytokine receptor-like factor 2 (CRLF2), and the mutant IL-7R proteins formed a functional receptor with CRLF2 for thymic stromal lymphopoietin (TSLP). Biochemical and functional assays reveal that these IL7R mutations are activating mutations conferring cytokine-independent growth of progenitor lymphoid cells. A cysteine, included in all but three of the mutated IL-7R alleles, is essential for the constitutive activation of the receptor. This is the first demonstration of gain-of-function mutations of IL7R. Our current and recent observations of mutations in IL7R and CRLF2, respectively suggest that the addition of cysteine to the juxtamembranous domains is a general mechanism for mutational activation of type I cytokine receptors in leukemia.

Multisensory visual-tactile object related network in humans: insights gained using a novel crossmodal adaptation approach.

Neuroimaging techniques have provided ample evidence for multisensory integration in humans. However, it is not clear whether this integration occurs at the neuronal level or whether it reflects areal convergence without such integration. To examine this issue as regards visuo-tactile object integration we used the repetition suppression effect, also known as the fMRI-based adaptation paradigm (fMR-A). Under some assumptions, fMR-A can tag specific neuronal populations within an area and investigate their characteristics. This technique has been used extensively in unisensory studies. Here we applied it for the first time to study multisensory integration and identified a network of occipital (LOtv and calcarine sulcus), parietal (aIPS), and prefrontal (precentral sulcus and the insula) areas all showing a clear crossmodal repetition suppression effect. These results provide a crucial first insight into the neuronal basis of visuo-haptic integration of objects in humans and highlight the power of using fMR-A to study multisensory integration using non-invasinve neuroimaging techniques.

A putative model of multisensory object representation.

This review surveys the recent literature on visuo-haptic convergence in the perception of object form, with particular reference to the lateral occipital complex (LOC) and the intraparietal sulcus (IPS) and discusses how visual imagery or multisensory representations might underlie this convergence. Drawing on a recent distinction between object- and spatially-based visual imagery, we propose a putative model in which LOtv, a subregion of LOC, contains a modality-independent representation of geometric shape that can be accessed either bottom-up from direct sensory inputs or top-down from frontoparietal regions. We suggest that such access is modulated by object familiarity: spatial imagery may be more important for unfamiliar objects and involve IPS foci in facilitating somatosensory inputs to the LOC; by contrast, object imagery may be more critical for familiar objects, being reflected in prefrontal drive to the LOC.