Elodie Sanchez

A new autoinflammatory and autoimmune syndrome associated with NLRP1 mutations: NAIAD (NLRP1-associated autoinflammation with arthritis and dyskeratosis)

Objectives Inflammasomes are multiprotein complexes that sense pathogens and trigger biological mechanisms to control infection. Nucleotide-binding oligomerisation domain-like receptor (NLR) containing a PYRIN domain 1 (NLRP1), NLRP3 and NLRC4 plays a key role in this innate immune system by directly assembling in inflammasomes and regulating inflammation. Mutations in NLRP3 and NLRC4 are linked to hereditary autoinflammatory diseases, whereas polymorphisms in NLRP1 are associated with autoimmune disorders such as vitiligo and rheumatoid arthritis. Whether human NLRP1 mutation is associated with autoinflammation remains to be determined. Methods To search for novel genes involved in systemic juvenile idiopathic arthritis, we performed homozygosity mapping and exome sequencing to identify causative genes. Immunoassays were performed with blood samples from patients. Results We identified a novel disease in three patients from two unrelated families presenting diffuse skin dyskeratosis, autoinflammation, autoimmunity, arthritis and high transitional B-cell level. Molecular screening revealed a non-synonymous homozygous mutation in NLRP1 (c.2176C>T; p.Arg726Trp) in two cousins born of related parents originating from Algeria and a de novo heterozygous mutation (c.3641C>G, p.Pro1214Arg) in a girl of Dutch origin. The three patients showed elevated systemic levels of caspase-1 and interleukin 18, which suggested involvement of NLRP1 inflammasome. Conclusions We demonstrate the responsibility of human NLRP1 in a novel autoinflammatory disorder that we propose to call NAIAD for NLRP1-associated autoinflammation with arthritis and dyskeratosis. This disease could be a novel autoimmuno-inflammatory disease combining autoinflammatory and autoimmune features. Our data, combined with that in the literature, highlight the pleomorphic role of NLRP1 in inflammation and immunity. Trial registration number NCT02067962; Results.

Mutation Update for Kabuki Syndrome Genes KMT2D and KDM6A and Further Delineation of X-Linked Kabuki Syndrome Subtype 2.

Kabuki syndrome (KS) is a rare but recognizable condition that consists of a characteristic face, short stature, various organ malformations, and a variable degree of intellectual disability. Mutations in KMT2D have been identified as the main cause for KS, whereas mutations in KDM6A are a much less frequent cause. Here, we report a mutation screening in a case series of 347 unpublished patients, in which we identified 12 novel KDM6A mutations (KS type 2) and 208 mutations in KMT2D (KS type 1), 132 of them novel. Two of the KDM6A mutations were maternally inherited and nine were shown to be de novo. We give an up‐to‐date overview of all published mutations for the two KS genes and point out possible mutation hot spots and strategies for molecular genetic testing. We also report the clinical details for 11 patients with KS type 2, summarize the published clinical information, specifically with a focus on the less well‐defined X‐linked KS type 2, and comment on phenotype–genotype correlations as well as sex‐specific phenotypic differences. Finally, we also discuss a possible role of KDM6A in Kabuki‐like Turner syndrome and report a mutation screening of KDM6C (UTY) in male KS patients.

Identification of a new exon 2-skipped TNFR1 transcript: regulation by three functional polymorphisms of the TNFR-associated periodic syndrome (TRAPS) gene

Background Mutations in the TNFRSF1A gene encoding the tumour necrosis factor α cell surface receptor, TNFR1, cause TNFR-associated periodic syndrome (TRAPS) and polymorphisms in TNFRSF1A, including rs4149570, rs767455 and rs1800692, are associated with inflammatory diseases. Objectives To describe a new exon 2-spliced transcript—TNFR1-d2—and the impact of these three single nucleotide polymorphisms on exon 2 splicing, transcriptional activity of TNFRSF1A and TRAPS phenotype. Methods Expression of TNFRSF1A transcripts was performed by reverse-transcription-PCR in a range of human cells and tissues. Exon 2 splicing and transcriptional activity were analysed in HEK293T and SW480 cells by in vitro alternative splicing and luciferase assays, respectively. We constructed haplotypes containing rs4149570, rs767455 and rs1800692 in controls (n=72), patients with TRAPS (n=111) and in TRAPS-like patients (n=450) to compare their distribution and association with clinical features of TRAPS. Results TNFR1-d2 was expressed in a tissue-specific manner, whereas TNFR1 expression was ubiquitous. Alternative splicing assays showed that the T-A-T haplotype at rs4149570–rs767455–rs1800692 had a significantly higher expression of exon 2-skipping product (p=0.02) compared with the G-G-C haplotype. Transcriptional activity from the T-T haplotype at rs4149570–rs1800692 was increased compared with the G-C haplotype (p=0.03). In patients with TRAPS, rs1800692 T/T homozygotes were excessively rare (p<10−4) and TRAPS-like patients with this genotype experienced less fever. Conclusions Our study provides a new mechanism of TNFRSF1A regulation whereby three polymorphisms in the promoter, exon 1 and intron 4 have a functional and combined effect on exon 2 splicing, via a coupling mechanism between transcription and splicing. These polymorphisms may affect the phenotype of TRAPS and TRAPS-like patients.

Clinical dose effect and functional consequences of R92Q in two families presenting with a TRAPS/PFAPA‐like phenotype

TNF receptor‐associated syndrome (TRAPS) is a dominantly inherited autoinflammatory condition caused by mutations in the TNFRSF1A gene. The mechanism underlying the variable expressivity of the common variant R92Q (rs4149584; c.362G>A; p.Arg121Gln) is unclear and is of critical importance for patient care and genetic counseling. This study evaluated the impact of the number of R92Q mutations in two unique unrelated families.

NLRP1 mutations cause autoinflammatory diseases in human

Inflammation is a vital and complex process in response to diverse tissue damaging stimuli such as trauma, injury and pathogen. NLRP1, NLRP3 and NLRC4 belonging to the intracellular proteins Nod like receptor family, are capable of sensing the inflammatory inducers and trigger the assembly of a large complex called the inflammasome. By inducing the caspase-1 activation, inflammasome plays a crucial role in the release of IL-1β and IL-18, two critical cytokines of the initial steps of inflammatory responsesand, in some cases, the induction of a pro-inflammatory cell death called pyroptosis. Whereas mutations in NLRP3 and NLRC4 have been linked to two rare monogenic systemic autoinflammatory diseases (SAIDs), several polymorphisms in the NLRP1 gene have been associated extensively to an increased risk of autoimmune disorders (e.g. vitiligo, psoriasis, type 1 diabetes, and rheumatoid arthritis). We identified for the first time two distinct NLRP1 mutations in patients displaying a novel systemic autoinflammatory disease (SAID) and a novel syndrome combining autoinflammation and autoimmunity.

07.16 Nlrp1 mutations cause autoinflammatory diseases in human: implication of the nlrp1 inflammasome?

Background Inflammation is a vital and complex process in response to diverse tissue damaging stimuli such as trauma, injury and pathogen. NLRP1, NLRP3 and NLRC4 belonging to the intracellular proteins Nod like receptor family, are capable of sensing the inflammatory inducers and trigger the assembly of a large complex called the inflammasome. By inducing the caspase-1 activation, inflammasome plays a crucial role in the release of IL-1β and IL-18, two critical cytokines of the initial steps of inflammatory responses. Whereas mutations in NLRP3 and NLRC4 have been linked to two rare monogenic systemic autoinflammatory diseases (SAIDs), several polymorphisms in the NLRP1 gene have been associated extensively to an increased risk of autoimmune disorders (e.g. vitiligo, psoriasis, type 1 diabetes, and rheumatoid arthritis). We identified for the first time two distinct NLRP1 mutations in patients displaying a novel SAID combining autoinflammation and autoimmunity. We named this disease NAIAD, for NLRP1-associated autoinflammation arthritis and dyskeratosis. The aim of our study was to unravel how mutation in NLRP1 impaired its function and triggered autoinflammation. Materials and methods Peripheral blood mononuclear cells from patients were analysed to identify the immunologic components involved in these novel diseases, using flow cytometry. The pathogenic effect of the NLRP1 mutations in inflammation was investigated using in vitro functional assays in transfected HEK293T. Results The level of caspase-1, IL-18 and IL-1β in serum samples from patients was increased as compared to controls and asymptomatic parents. Moreover, patient’s cells displayed constitutive production of IL-1β. Functional studies in HEK293T revealed that the NLRP1 mutations resulted in a constitutive activation of the NLRP1 inflammasome. Conclusions We demonstrated that two mutations in the NLRP1 gene are involved in autoinflammation in human. This novel disease could be a novel inflammasomopathy combining autoinflammatory and autoimmune features. Our data, combined with that in the literature, highlight the pleomorphic role of NLRP1 in inflammation and immunity.

Identification of rare genetic variants in Juvenile Idiopathic Arthritis using whole exome sequencing

Juvenile Idiopathic Arthritis (JIA) is the most common form of chronic arthritis in children. JIA is characterized by onset of disease before the age of 16, with arthritis lasting >6 weeks, and with an unknown cause. Among JIA, seven sub-groups based on clinical and biological features have been individualized namely: systemic arthritis (sJIA) with autoinflammatory conditions, persistent and extended oligoarthritis (per-oJIA and ext-oJIA, respectively), rheumatoid factor-positive polyarthritis (RFpos-pJIA), enthesitis-related arthritis (ERA), psoriatic arthritis (PsA), and undifferentiated arthritis. Physiopathology of JIA is complex and JIA is considered to be a multifactorial disease due to the combination of genetic and environmental factors. Searching for genetic factors in JIA during the last decade, the introduction of genome-wide association studies (GWAS) and whole-exome sequencing have discovered several new loci associated with JIA susceptibility and have identified the disease-associated gene monogenic form of sJIA, respectively. However, despite these novel knowledge, our understanding of JIA pathogenesis still remains poorly elusive and accumulating evidence supports genetic variability as playing a key role in JIA development.

Characterization of the TNFR1-d2 protein: Implication in TNF receptor associated periodic syndrome (TRAPS)?

Binding of TNF to TNF receptor 1 (TNFR1) induces both the survival pathway by activation of the NF-kB transcription factor, and the death pathway by apoptosis. Mutations in the TNFR1 gene (TNFSFR1A) are responsible for the auto-inflammatory disease TRAPS, a dominantly inherited hereditary recurrent fever. Various defects such as defective TNFR1 receptor shedding, protein misfolding, NF-kB activation, or apoptosis have been associated with the pathogenesis of TRAPS. Previously, we have identified TNFR1-d2, an exon2-spliced transcript of TNFRSF1A. TNFR1-d2 is expressed in a tissue-specific manner in contrast to ubiquitous expression of the full-length TNFR1 transcript.

OR10-002 - A novel TNFR1 transcript of TRAPS gene

Mutations in the TNFRSF1A gene encoding the TNF cell surface receptor, TNFR1, cause TNFR-associated periodic syndrome (TRAPS) and polymorphisms in TNFRSF1A, including rs4149570, rs767455 and rs1800692, are associated with inflammatory diseases.