Naturally occurring mutation affecting the MyD88-binding site of TNFRSF13B impairs triggering of class switch recombination

Mutations in the transmembrane activator and calcium-modulating cyclophilin ligand interactor (TACI) were previously found to be associated with hypogammaglobulinemia in humans. It has been shown that proliferation inducing ligand (APRIL) elicits class switch recombination (CSR) by inducing recruitment ofMyD88 to a TACI highly conserved cytoplasmic domain (THC). We have identified a patient with hypogammaglobulinemia carrying a missense mutation (S231R) predicted to affect the THC. Aiming to evaluate the relevance of this novel mutation of TACI in CSR induction, we tested the ability of TACI, TLR9, or/and CD40 ligands to trigger CSR in naive B cells and B-cell lines carrying S231R. IgG secretion was impaired when triggered by TACI or/and TLR9 ligands on S231R-naive B cells. Likewise, these stimuli induced less expression of activation-induced cytidine deaminase, I(γ)1-C(μ), and I(γ)1-C(μ), while induction by optimal CD40 stimulation was indistinguishable from controls. These cells also showed an impaired cooperation between TACI and TLR9 pathways, as well as a lack of APRIL-mediated enhancement of CD40 activation in suboptimal conditions. Finally, after APRIL ligation, S231R-mutated TACI failed to colocalize withMyD88. Collectively, these results highlight the requirement of an intact MyD88-binding site in TACI to trigger CSR.Fil: Almejún, María Belén. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cols, Montserrat. Mount Sinai School of Medicine. Department of Medicine; Estados UnidosFil: Zelazko, Marta. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Oleastro, Matías. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Cerutti, Andrea. Mount Sinai School of Medicine. Department of Medicine; Estados UnidosFil: Oppezzo, Pablo. Instituto Pasteur. Unidad de Proteínas Recombinantes; UruguayFil: Cunningham Rundles, Charlotte. Mount Sinai School of Medicine. Department of Medicine; Estados UnidosFil: Danielian, Silvia. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; Argentin

Immunological characteristics and two novel mutations in TACI in a cohort of 28 pediatric patients with common variable immunodeficiency

Common variable immunodeficiency (CVID) is a heterogeneous syndrome characterized by impaired immunoglobulin production. Mutations in the gene encoding TACI (TNFRSF13B) were previously found to be associated with CVID. Previous studies have identified a variety of sequence variants in TACI where A181E and C104R were the most common, with variable frequencies in different ethnic populations. So far, no mutations were identified in the recently reported “TACI highly conserved” (THC) cytoplasmic domain, important for the induction of class switch recombination. Our study evaluated immunological and clinical data on a cohort of 28 Argentinean pediatric CVID patients and allowed the identification of two novel mutations in TNFRSF13B, including one, S231R, affecting the highly conserved THC domain. In contrast, none of the patients presented with A181E and C104R mutations.Fil: Almejún, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; ArgentinaFil: Sajaroff, Elisa Olga. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; ArgentinaFil: Galicchio, Miguel. Hospital de Niños Víctor J Vilela; ArgentinaFil: Oleastro, Matías. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; ArgentinaFil: Bernasconi, Andrea Raquel. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; ArgentinaFil: Zelazko, Marta. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; ArgentinaFil: Danielian, Silvia. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; Argentin

Expanding spectrum, intrafamilial diversity, and therapeutic challenges from 15 patients with heterozygous CARD11-associated diseases: A single center experience

CARD11-associated diseases are monogenic inborn errors of immunity involving immunodeficiency, predisposition to malignancy and immune dysregulation such as lymphoproliferation, inflammation, atopic and autoimmune manifestations. Defects in CARD11 can present as mutations that confer a complete or a partial loss of function (LOF) or contrarily, a gain of function (GOF) of the affected gene product. We report clinical characteristics, immunophenotypes and genotypes of 15 patients from our center presenting with CARD11-associated diseases. Index cases are pediatric patients followed in our immunology division who had access to next generation sequencing studies. Variant significance was defined by functional analysis in cultured cells transfected with a wild type and/or with mutated hCARD11 constructs. Cytoplasmic aggregation of CARD11 products was evaluated by immunofluorescence. Nine index patients with 9 unique heterozygous CARD11 variants were identified. At the time of the identification, 7 variants previously unreported required functional validation. Altogether, four variants showed a GOF effect as well a spontaneous aggregation in the cytoplasm, leading to B cell expansion with NF-κB and T cell anergy (BENTA) diagnosis. Additional four variants showing a LOF activity were considered as causative of CARD11-associated atopy with dominant interference of NF-kB signaling (CADINS). The remaining variant exhibited a neutral functional assay excluding its carrier from further analysis. Family segregation studies expanded to 15 individuals the number of patients presenting CARD11-associated disease. A thorough clinical, immunophenotypical, and therapeutic management evaluation was performed on these patients (5 BENTA and 10 CADINS). A remarkable variability of disease expression was clearly noted among BENTA as well as in CADINS patients, even within multiplex families. Identification of novel CARD11 variants required functional studies to validate their pathogenic activity. In our cohort BENTA phenotype exhibited a more severe and expanded clinical spectrum than previously reported, e.g., severe hematological and extra hematological autoimmunity and 3 fatal outcomes. The growing number of patients with dysmorphic facial features strengthen the inclusion of extra-immune characteristics as part of the CADINS spectrum. CARD11-associated diseases represent a challenging group of disorders from the diagnostic and therapeutic standpoint, especially BENTA cases that can undergo a more severe progression than previously described.Fil: Urdinez, Luciano. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Erra, Lorenzo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Palma, Alejandro Martín. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Mercogliano, María Florencia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biociencias, Biotecnología y Biología Traslacional; ArgentinaFil: Fernández, Julieta Belén. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biociencias, Biotecnología y Biología Traslacional; ArgentinaFil: Prieto, Emma. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; ArgentinaFil: Goris, Verónica. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; ArgentinaFil: Bernasconi, Andrea Raquel. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Sanz, Marianela. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Villa, Mariana Natalia. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Bouzo, Carolina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Caputi, Lucía. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Quesada, Belén. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Solís, Daniel. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; ArgentinaFil: Aguirre Bruzzo, Anabel. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Katsicas, Maria Martha. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Galluzzo, Laura. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Weyersberg, Christian. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Bocian, Marcela. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Bujan, Maria Marta. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Oleastro Matías. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan". Laboratorio de Investigación; ArgentinaFil: Almejún, María Belén. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biociencias, Biotecnología y Biología Traslacional; ArgentinaFil: Danielian, Silvia. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatria "juan P.garrahan". Laboratorio de Biología Molecular y Cultivo Celular; Argentin

Noninfectious complications in patients with pediatric-onset common variable immunodeficiency correlated with defects in somatic hypermutation but not in class-switch recombination

Background Common variable immunodeficiency (CVID) is a heterogeneous syndrome characterized by impaired immunoglobulin production and usually presents with a normal quantity of peripheral B cells. Most attempts aiming to classify these patients have mainly been focused on T- or B-cell phenotypes and their ability to produce protective antibodies, but it is still a major challenge to find a suitable classification that includes the clinical and immunologic heterogeneity of these patients. Objective In this study we evaluated the late stages of B-cell differentiation in a heterogeneous population of patients with pediatric-onset CVID to clinically correlate and assess their ability to perform somatic hypermutation (SHM), class-switch recombination (CSR), or both. Methods We performed a previously reported assay, the restriction enzyme hotspot mutation assay (IgκREHMA), to evaluate in vivo SHM status. We amplified switch regions from genomic DNA to investigate the quality of the double-strand break repairs in the class-switch recombination process in vivo. We also tested the ability to generate immunoglobulin germline and circle transcripts and to upregulate the activation-induced cytidine deaminase gene through in vitro T-dependent and T-independent stimuli. Results Our results showed that patients could be classified into 2 groups according to their degree of SHM alteration. This stratification showed a significant association between patients of group A, severe alteration, and the presence of noninfectious complications. Additionally, 60% of patients presented with increased microhomology use at switched regions. In vitro activation revealed that patients with CVID behaved heterogeneously in terms of responsiveness to T-dependent stimuli. Conclusions The correlation between noninfectious complications and SHM could be an important tool for physicians to further characterize patients with CVID. This categorization would help to improve elucidation of the complex mechanisms involved in B-cell differentiation pathways.Fil: Almejún, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Campos, Bárbara Carolina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Patiño, Virginia. Instituto Pasteur; UruguayFil: Galicchio, Miguel. Hospital de Niños Víctor J. Vilela; ArgentinaFil: Zelazko, Marta. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Oleastro, Matías. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Oppezzo, Pablo. Instituto Pasteur; UruguayFil: Danielian, Silvia. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentin

Wiskott-Aldrich Syndrome. A Report of a New Mutation

Wiskott-Aldrich syndrome was rst reported clinically in 1937, and in 1954 the classic triad was identified: eccema, recurrent infections and thrombocytopenia with an X-linked transmission. Its incidence is estimated at 1 to 10 in one million live births per year. Wiskott Aldrich syndrome is caused by mutations in a gene in the short arm of chromosome X that encodes the Wiskott-Aldrich syndrome protein (WASp), which identi cation and sequencing was rst performed in 1994, and since then about 300 mutations have been reported. This paper describes the case of a boy with Wiskott-Aldrich syndrome, with clinical and genetic diagnosis, with a considerable diagnostic delay attributable to an atypical presentation misdiagnosed as immune thrombocytopenia

Inherited human Apollo deficiency causes severe bone marrow failure and developmental defects

International audienceInherited bone marrow failure syndromes (IBMFS) represent a group of disorders typified by impaired production of one or several blood cell types. The telomere biology disorders dyskeratosis congenita (DC) and its severe variant Høyeraal-Hreidarsson (HH) syndrome are rare IBMFS characterized by bone marrow failure, developmental defects, and various premature aging complications associated with critically short telomeres. Here we identified biallelic variants in the gene encoding the 5'-to-3' DNA exonuclease Apollo/SNM1B in three unrelated patients presenting with a DC/HH phenotype consisting of early onset hypocellular bone marrow failure, B and NK lymphopenia, developmental anomalies, microcephaly and/or intrauterine growth retardation. All three patients carry a homozygous or compound heterozygous (in combination with a null-allele) missense variant affecting the same residue L142 (L142F or L142S) located in the catalytic domain of Apollo. Apollo-deficient cells from patients exhibited spontaneous chromosome instability and impaired DNA repair that was complemented by CRISPR/Cas9-mediated gene correction. Furthermore, patients' cells showed signs of telomere fragility that were however not associated with global reduction of telomere length. Unlike patients' cells, human Apollo KO HT1080-cell lines showed strong telomere dysfunction accompanied by excessive telomere shortening, suggesting that the L142S and L142F Apollo variants are hypomorphic. Collectively, these findings define human Apollo as a genome caretaker and identify biallelic Apollo variants as a genetic cause of a hitherto unrecognized severe IBMFS combining clinical hallmarks of DC/HH with normal telomere length

Identification of Germline Non-coding Deletions in XIAP Gene Causing XIAP Deficiency Reveals a Key Promoter Sequence

International audiencePurposeX-linked inhibitor of apoptosis protein (XIAP) deficiency, also known as the X-linked lymphoproliferative syndrome of type 2 (XLP-2), is a rare immunodeficiency characterized by recurrent hemophagocytic lymphohistiocytosis, splenomegaly, and inflammatory bowel disease. Variants in XIAP including missense, non-sense, frameshift, and deletions of coding exons have been reported to cause XIAP deficiency. We studied three young boys with immunodeficiency displaying XLP-2-like clinical features. No genetic variation in the coding exons of XIAP was identified by whole-exome sequencing (WES), although the patients exhibited a complete loss of XIAP expression.MethodsTargeted next-generation sequencing (NGS) of the entire locus of XIAP was performed on DNA samples from the three patients. Molecular investigations were assessed by gene reporter expression assays in HEK cells and CRISPR-Cas9 genome editing in primary T cells.ResultsNGS of XIAP identified three distinct non-coding deletions in the patients that were predicted to be driven by repetitive DNA sequences. These deletions share a common region of 839 bp that encompassed the first non-coding exon of XIAP and contained regulatory elements and marks specific of an active promoter. Moreover, we showed that among the 839 bp, the exon was transcriptionally active. Finally, deletion of the exon by CRISPR-Cas9 in primary cells reduced XIAP protein expression.ConclusionsThese results identify a key promoter sequence contained in the first non-coding exon of XIAP. Importantly, this study highlights that sequencing of the non-coding exons that are not currently captured by WES should be considered in the genetic diagnosis when no variation is found in coding exons