DOCK11 deficiency in patients with X-linked actinopathy and autoimmunity.

Dedicator of cytokinesis (DOCK) proteins play a central role in actin cytoskeleton regulation. This is highlighted by the DOCK2 and DOCK8 deficiencies leading to actinopathies and immune deficiencies. DOCK8 and DOCK11 activate CDC42, a Rho-guanosine triphosphate hydrolases involved in actin cytoskeleton dynamics, among many cellular functions. The role of DOCK11 in human immune disease has been long suspected but, to the best of our knowledge, has never been described to date. We studied 8 male patients, from 7 unrelated families, with hemizygous DOCK11 missense variants leading to reduced DOCK11 expression. The patients were presenting with early-onset autoimmunity, including cytopenia, systemic lupus erythematosus, skin, and digestive manifestations. Patients' platelets exhibited abnormal ultrastructural morphology and spreading as well as impaired CDC42 activity. In vitro activated T cells and B-lymphoblastoid cell lines from patients exhibited aberrant protrusions and abnormal migration speed in confined channels concomitant with altered actin polymerization during migration. Knock down of DOCK11 recapitulated these abnormal cellular phenotypes in monocytes-derived dendritic cells and primary activated T cells from healthy controls. Lastly, in line with the patients' autoimmune manifestations, we also observed abnormal regulatory T-cell (Treg) phenotype with profoundly reduced FOXP3 and IKZF2 expression. Moreover, we found reduced T-cell proliferation and impaired STAT5B phosphorylation upon interleukin-2 stimulation of the patients' lymphocytes. In conclusion, DOCK11 deficiency is a new X-linked immune-related actinopathy leading to impaired CDC42 activity and STAT5 activation, and is associated with abnormal actin cytoskeleton remodeling as well as Treg phenotype, culminating in immune dysregulation and severe early-onset autoimmunity.

CALR mutant protein rescues the response of MPL p.R464G variant associated with CAMT to eltrombopag.

Congenital amegakaryocytic thrombocytopenia (CAMT) is a severe inherited thrombocytopenia due to loss-of-function mutations affecting the thrombopoietin (TPO) receptor, MPL. Here, we report a new homozygous MPL variant responsible for CAMT in 1 consanguineous family. The propositus and her sister presented with severe thrombocytopenia associated with mild anemia. Next-generation sequencing revealed the presence of a homozygous MPLR464G mutation resulting in a weak cell-surface expression of the receptor in platelets. In cell lines, we observed a defect in MPLR464G maturation associated with its retention in the endoplasmic reticulum. The low cell-surface expression of MPLR464G induced very limited signaling with TPO stimulation, leading to survival and reduced proliferation of cells. Overexpression of a myeloproliferative neoplasm-associated calreticulin (CALR) mutant did not rescue trafficking of MPLR464G to the cell surface and did not induce constitutive signaling. However, it unexpectedly restored a normal response to eltrombopag (ELT), but not to TPO. This effect was only partially mimicked by the purified recombinant CALR mutant protein. Finally, the endogenous CALR mutant was able to restore the megakaryocyte differentiation of patient CD34+ cells carrying MPLR464G in response to ELT.

Cardiac valve involvement in ADAR-related type I interferonopathy.

BACKGROUND: Adenosine deaminases acting on RNA (ADAR) mutations cause a spectrum of neurological phenotypes ranging from severe encephalopathy (Aicardi-Goutières syndrome) to isolated spastic paraplegia and are associated with enhanced type I interferon signalling. In children, non-neurological involvement in the type I interferonopathies includes autoimmune and rheumatological phenomena, with calcifying cardiac valve disease only previously reported in the context of MDA5 gain-of-function. RESULTS: We describe three patients with biallelic ADAR mutations who developed calcifying cardiac valvular disease in late childhood (9.5-14 years). Echocardiography revealed progressive calcification of the valvular leaflets resulting in valvular stenosis and incompetence. Two patients became symptomatic with biventricular failure after 5-6.5 years. In one case, disease progressed to severe cardiac failure despite maximal medical management, with death occurring at 17 years. Another child received mechanical mitral and aortic valve replacement at 16 years with good postoperative outcome. Histological examination of the affected valves showed fibrosis and calcification. CONCLUSIONS: Type I interferonopathies of differing genetic aetiology demonstrate an overlapping phenotypic spectrum which includes calcifying cardiac valvular disease. Individuals with ADAR-related type I interferonopathy may develop childhood-onset multivalvular stenosis and incompetence which can progress insidiously to symptomatic, and ultimately fatal, cardiac failure. Regular surveillance echocardiograms are recommended to detect valvular disease early.

Artificial intelligence outperforms experienced nephrologists to assess dry weight in pediatric patients on chronic hemodialysis.

BACKGROUND: Dry weight is the lowest weight patients on hemodialysis can tolerate; correct dry weight estimation is necessary to minimize morbi-mortality, but is difficult to achieve. Here, we used artificial intelligence to improve the accuracy of dry weight assessment in hemodialysis patients. METHODS/RESULTS: We designed a neural network which used bio-impedancemetry, blood volume monitoring, and blood pressure values as inputs; output was artificial intelligence dry weight. Fourteen pediatric patients were switched from nephrologist to artificial intelligence dry weight. Artificial intelligence dry weight was higher (28.6%), lower (50%), or identical to nephrologist dry weight. Mean difference between artificial intelligence and nephrologist dry weights was 0.497 kg (- 1.33 to + 1.29 kg). In patients for whom artificial intelligence dry weight was lower than nephrologist dry weight, systolic blood pressure significantly decreased after dry weight decrease to artificial intelligence dry weight (77th to 60th percentile, p = 0.022); anti-hypertensive treatments were successfully decreased or discontinued in 28.7% of cases. In patients for whom artificial intelligence dry weight was higher than nephrologist dry weight, no hypertension was observed after dry weight increase to artificial intelligence dry weight; when present, symptoms of dry weight underestimation receded. CONCLUSIONS: Neural network predictions outperformed those of experienced nephrologists in most cases, proving artificial intelligence is a powerful tool for predicting dry weight in hemodialysis patients.

Somatic RAP1B gain-of-function variant underlies isolated thrombocytopenia and immunodeficiency.

The ubiquitously expressed small GTPase Ras-related protein 1B (RAP1B) acts as a molecular switch that regulates cell signaling, cytoskeletal remodeling, and cell trafficking and activates integrins in platelets and lymphocytes. The residue G12 in the P-loop is required for the RAP1B-GTPase conformational switch. Heterozygous germline RAP1B variants have been described in patients with syndromic thrombocytopenia. However, the causality and pathophysiological impact remained unexplored. We report a boy with neonatal thrombocytopenia, combined immunodeficiency, neutropenia, and monocytopenia caused by a heterozygous de novo single nucleotide substitution, c.35G>A (p.G12E) in RAP1B. We demonstrate that G12E and the previously described G12V and G60R were gain-of-function variants that increased RAP1B activation, talin recruitment, and integrin activation, thereby modifying late responses such as platelet activation, T cell proliferation, and migration. We show that in our patient, G12E was a somatic variant whose allele frequency decreased over time in the peripheral immune compartment, but remained stable in bone marrow cells, suggesting a differential effect in distinct cell populations. Allogeneic hematopoietic stem cell transplantation fully restored the patient's hemato-immunological phenotype. Our findings define monoallelic RAP1B gain-of-function variants as a cause for constitutive immunodeficiency and thrombocytopenia. The phenotypic spectrum ranged from isolated hematological manifestations in our patient with somatic mosaicism to complex syndromic features in patients with reported germline RAP1B variants.

Compound heterozygous mutations in the kinase domain of IKKα lead to immunodeficiency and immune dysregulation.

IKKα, encoded by CHUK , is crucial in the non-canonical NF-κB pathway and part of the IKK complex activating the canonical pathway alongside IKKß. Absence of IKKα cause fetal encasement syndrome in human, fatal in utero, while an impaired IKKα-NIK interaction was reported in a single patient and cause combined immunodeficiency. Here, we describe compound heterozygous variants in the kinase domain of IKKα in a female patient with hypogammaglobulinemia, recurrent lung infections, and Hay-Wells syndrome-like features. We showed that both variants were loss-of-function. Non-canonical NF-κB activation was profoundly diminished in stromal and immune cells while the canonical pathway was partially impaired. Reintroducing wild-type CHUK restored non-canonical NF-κB activation. The patient had neutralizing autoantibodies against type I IFN, akin to non-canonical NF-κB pathway deficiencies. Thus, this is the first case of bi-allelic CHUK mutations disrupting IKKα kinase function, broadening non-canonical NF-κB defect understanding and suggesting IKKα's role in canonical NF-κB target gene expression in human.

Single-cell RNA-sequencing of PBMCs from SAVI patients reveals disease-associated monocytes with elevated integrated stress response.

Gain-of-function mutations in stimulator of interferon gene 1 (STING1) result in STING-associated vasculopathy with onset in infancy (SAVI), a severe autoinflammatory disease. Although elevated type I interferon (IFN) production is thought to be the leading cause of the symptoms observed in patients, STING can induce a set of pathways, which have roles in the onset and severity of SAVI and remain to be elucidated. To this end, we performed a multi-omics comparative analysis of peripheral blood mononuclear cells (PBMCs) and plasma from SAVI patients and healthy controls, combined with a dataset of healthy PBMCs treated with IFN-ß. Our data reveal a subset of disease-associated monocyte, expressing elevated CCL3, CCL4, and IL-6, as well as a strong integrated stress response, which we suggest is the result of direct PERK activation by STING. Cell-to-cell communication inference indicates that these monocytes lead to T cell early activation, resulting in their senescence and apoptosis. Last, we propose a transcriptomic signature of STING activation, independent of type I IFN response.

Oscillation Transmission of Modern High-Frequency Neonatal Ventilators Under Different Lung Mechanics Conditions.

BACKGROUND: High-frequency oscillatory ventilation (HFOV) is widely used in neonatal critical care, and several modern ventilators using different technologies are available to provide HFOV. These devices have different technical characteristics that might interact with patient lung mechanics to influence the effectiveness of ventilation. To verify this, we studied the oscillation transmission of 5 neonatal oscillators in a lung model mimicking the mechanical patterns commonly observed in neonatal practice. METHODS: This was a benchtop, in vitro, physiological, pragmatic study using a model mimicking airways and lung of a 1-kg preterm neonate and the following patterns: normal (compliance: 1.0 mL/cm H2O, resistance: 50 cm H2O/L/s), restrictive (compliance: 0.3 mL/cm H2O, resistance: 50 cm H2O/L/s), and mixed mechanics (compliance: 0.3 mL/cm H2O, resistance: 250 cm H2O/L/s). Several permutations of HFOV parameters (variable mean airway pressure or amplitude or frequency protocols) were tested. Oscillations were measured with a dedicated pressure transducer validated for use during HFOV, and oscillatory pressure ratio (OPR) was calculated to estimate the oscillation transmission. RESULTS: Overall OPR (calculated on all experiments) was significantly different between ventilators and the mechanical patterns (both P < .001). Different ventilators and patterns accounted for 35.6% and 20.6% of the variation in oscillation transmission, respectively. Sub-analyses per changing amplitude or frequency protocols and multivariate regressions showed that VN500 (standardized ß coefficient [St.ß]: 0.548, P < .001) and Fabian HFO (St.ß: 0.421, P < .001; adjusted R2: 0.615) provided the best oscillation transmission. Fabian HFO also delivered oscillations with the lowest variability when increasing amplitude. CONCLUSIONS: In an experimental setting mimicking typical neonatal lung disorders, the oscillation transmission was more dependent on the ventilator model than on the mechanical lung conditions at equal HFOV parameters. Fabian HFO and VN500 provided better oscillation transmission overall, and when increasing amplitude, Fabian HFO delivered oscillations with the lowest variability.

Sustained remission after haploidentical bone marrow transplantation in a child with refractory systemic juvenile idiopathic arthritis.

BACKGROUND: Some patients with systemic juvenile idiopathic arthritis (SJIA) and severe, refractory disease achieved remission through intensive immunosuppressive treatment followed by autologous hematopoietic stem cell transplantation (HSCT). However, disease relapsed in most cases. More recently selected SJIA patients received allogenic HSCT from a HLA-identical sibling or a HLA matched unrelated donor. While most transplanted patients achieved sustained SJIA remission off-treatment, the procedure-related morbidity was high. CASE REPORT: A girl presented SJIA with a severe disease course since the age of 15 months. She was refractory to the combination of methotrexate and steroids to anti-interleukin (IL)-1, then anti-IL-6, tumor necrosis factor alpha inhibitors, and thalidomide. Given the high disease burden and important treatment-related toxicity the indication for a haploidentical HSCT from her mother was validated, as no HLA matched donor was available. The patient received a T replete bone marrow graft at the age of 3.7 years. Conditioning regimen contained Rituximab, Alemtuzumab, Busulfan, and Fludarabine. Cyclophosphamide at D + 3 and + 4 post HSCT was used for graft-versus-host-disease prophylaxis, followed by Cyclosporin A and Mycophenolate Mofetil. Post HSCT complications included severe infections, grade 3 intestinal graft-versus-host-disease, autoimmune thyroiditis, and immune thrombocytopenia. Three years after HSCT, the child is alive and well, notwithstanding persistent hypothyroidy requiring substitution. Immune thrombocytopenia had resolved. Most importantly, SJIA was in complete remission, off immunosuppressive drugs. CONCLUSION: Allogenic HSCT may be a therapeutic option, even with a HLA haplo-identical alternative donor, in patients with inflammatory diseases such as SJIA. Despite increased experience with this treatment, the risk of life-threatening complications restrains its indication to selected patients with severe, refractory disease.