Explore the vast range of titles available.

Autoimmunity can occur when a checkpoint of self-tolerance fails. The study of familial autoimmune diseases can reveal pathophysiological mechanisms involved in more common autoimmune diseases. Here, by whole-exome/genome sequencing we identify heterozygous, autosomal-dominant, germline loss-of-function mutations in the SOCS1 gene in ten patients from five unrelated families with early onset autoimmune manifestations. The intracellular protein SOCS1 is known to downregulate cytokine signaling by inhibiting the JAK-STAT pathway. Accordingly, patient-derived lymphocytes exhibit increased STAT activation in vitro in response to interferon-γ, IL-2 and IL-4 that is reverted by the JAK1/JAK2 inhibitor ruxolitinib. This effect is associated with a series of in vitro and in vivo immune abnormalities consistent with lymphocyte hyperactivity. Hence, SOCS1 haploinsufficiency causes a dominantly inherited predisposition to early onset autoimmune diseases related to cytokine hypersensitivity of immune cells. SOCS1 is a potent suppressor of JAK-STAT signalling responses to IFNγ and γ-chain cytokines and thereby limits inflammation. Here the authors identify and characterize heterozygous SOCS1 mutations in 10 patients from 5 unrelated families with autoimmune diseases.

BackgroundHereditary haemorrhagic telangiectasia (HHT) and juvenile polyposis syndrome (JPS) can be caused by SMAD4 pathogenic variants. SMAD4 is a common transcription factor of the BMP/TGFβ signalling pathway. In this study, we developed a cell-based functional assay to address the pathogenicity of SMAD4 variants identified in the French HHT cohort.Methods SMAD4 variants were generated by site-directed mutagenesis. A functional assay was developed in a cell line that does not express SMAD4, and the different SMAD4 variants were tested for their capacity to activate the BMP and TGFβ response using luciferase reporter assays.ResultsTwelve SMAD4 variants were identified and studied. We were able to develop a robust functional assay for these variants. All the expressed variants resulted in loss of function (LOF) in response to BMP9 or TGFβ1 stimulation. SMAD4 variants within the MH2 domain expressed SMAD4 mutated proteins that were unable to hetero-oligomerise with other SMADs, which could explain their LOF. Finally, we tested primary human endothelial cells isolated from patients with HHT carrying SMAD4 heterozygous pathogenic variants and observed that they behaved like the control cells at rest or when stimulated with BMP9.ConclusionWe developed a SMAD4 functional assay that allows discrimination between benign and pathogenic SMAD4 variants. We demonstrated that the underlying molecular mechanism of this pathogenicity is due mostly to a loss of hetero-oligomerisation. This assay will be transferable to clinical genetic laboratories and will improve the diagnosis of patients with HHT–JPS.

Retinal dystrophy, optic nerve oedema, splenomegaly, anhidrosis and migraine headache (ROSAH) syndrome is an autosomal dominant disorder and to date is known to be caused by either the Thr237Met or Tyr254Cys variant in the protein kinase ALPK1. Here, we identify a family in which ROSAH syndrome is caused by a novel variant in which Ser277 is changed to Phe. All six patients examined display ocular inflammation and optic nerve elevation, four have retinal degeneration and four are registered blind. In contrast to wild-type ALPK1, which is activated specifically by bacterial ADP-heptose, ALPK1[Ser277Phe] is also activated by the human metabolites UDP-mannose and ADP-ribose and more strongly than the most frequent ROSAH-causing variant (ALPK1[Thr237Met]) but, unlike ALPK1[Thr237Met], ALPK1[Ser277Phe] is also activated by GDP-mannose. These observations can explain why ALPK1 variants causing ROSAH syndrome display constitutive activity in human cells. The side chains of Ser277 and Tyr254 interact in the crystal structure of ALPK1, but mutational analysis established that it is not the loss of this hydrogen bond between Ser277 and Tyr254 that alters the specificity of the ADP-heptose-binding pocket in the Ser277Phe and Tyr254Cys variants. The characterization of ALPK1 variants that cause ROSAH syndrome suggests ways in which drugs that selectively inhibit these disease-causing variants may be developed.

The aim of this study was to explore the impact of rare and ultra‐rare genetic variants on the understanding and treatment of autoimmune and autoinflammatory diseases with a focus on systemic lupus erythematosus (SLE) and Behçet syndrome. This review summarizes current research on the monogenic causes of SLE and Behçet syndrome, highlighting the various pathways that can be responsible for these unique phenotypes. In monogenic SLE, the identification of complement and DNASE1L3 deficiencies has elucidated mechanisms of apoptotic body accumulation and extracellular nucleic acid sensing. Type I interferonopathies underline the specific role of DNA/RNA sensing and the interferon overexpression in the development of systemic autoimmunity. Other significant genetic defects include Toll‐like receptor hypersignaling and JAK/STATopathies, which contribute to the breakdown of immune tolerance. To date, genetic defects directly affecting B and T cell biology only account for a minority of identified causes of monogenic lupus, highlighting the importance of a tight regulation of mechanistic target of rapamycin and RAS (Rat sarcoma GTPase)/MAPK (mitogen‐activated protein kinase) signaling in lupus. In Behçet syndrome, rare variants in TNFAIP3, RELA, and NFKB1 genes have been identified, underscoring the importance of NF‐κB overactivation. Additional monogenic diseases such as ELF4, WDR1 mutations and trisomy 8 further illustrate the genetic complexity of this condition. Observations from genetic studies in SLE and Behçet syndrome highlight the complexity of systemic inflammatory diseases in which distinct molecular defects caused by single‐gene mutations can promote lupus or Behçet syndromes, often unrecognizable from their genetically complex “classical” forms. Insights gained from studying rare genetic variants enhance our understanding of immune function in health and disease, paving the way for targeted therapies and personalized medicine.

Objectives Hypocomplementaemic urticarial vasculitis (HUV) is a rare small-vessel vasculitis characterized by the combination of urticarial vasculitis and hypocomplementaemia. HUV may occur in isolation or be associated with systemic diseases such as systemic lupus erythematosus (SLE). Recently, loss-of-function variants in DNASE1L3 have been reported to cause familial forms of HUV. We aimed to describe the clinical and genetic features of childhood-onset HUV cases in France. Methods We conducted a nationwide retrospective study in France that included 10 patients with childhood-onset HUV. Results Ten children, all girls, were included. Their median age at onset was 9.5 years (range: 2–14 years), and the median delay between onset and diagnosis was 13 months (range: 6–55 months). Phenotypes were heterogeneous: 3 had systemic HUV syndrome (S-HUVS), all associated with DNASE1L3 deficiency, including 2 siblings; 4 had non-systemic HUVS (NS-HUVS), one of whom had a C2 deficiency; and 3 had SLE-associated HUV. Musculoskeletal features were the most common extracutaneous manifestation (9/10). The most severe manifestations were observed in children with S-HUVS, including pulmonary haemorrhage (2/3) and glomerulonephritis (2/3). Anti-nuclear antibodies were positive in 9/10 patients, anti-C1q antibodies in 6/10, and anti-neutrophil cytoplasmic antibodies in 5/10. Antihistamines were widely used in NS-HUVS, while S-HUVS and SLE-associated HUV required immunosuppressive treatments. Hydroxychloroquine was used in 8/10 patients. Conclusion These 10 cases highlight the heterogeneity and potential severity of childhood-onset HUV. We report the third familial form of HUVS associated with DNASE1L3 deficiency and an extremely rare case of HUVS associated with C2 deficiency. Key messages Childhood-onset HUV is a rare disease with phenotypic and genotypic heterogeneity. Systemic HUVS, associated with DNASE1L3 deficiency but not with positive anti-C1q, is the most severe form. A genetic testing should be systematically performed in childhood-onset HUV.

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare vascular disease mainly caused by pathogenic mutations in ACVRL1 and ENG genes. Despite advances in HHT diagnosis, the molecular origin of some cases remains unclear. Recently, we observed a high prevalence of HHT-causing 5’UTR variants in ENG . These variants commonly introduce upstream AUG codons (uAUGs) at the origin of upstream open reading frames (upORFs) overlapping the coding sequence, all terminating at the same stop codon located at position c.125 (uAUG-c.125). Here, we analyzed all 5’UTR ENG single nucleotide variants that could alter upORFs in silico. Interestingly, we found that 85% of uAUG-c.125 variants alter the protein levels. Furthermore, we identified 2 variants creating uAUG-c.125 and uCUG-c.125 in HHT patients and experimentally demonstrated their association with reduced endoglin levels This study provides new elements for the interpretation of upORF-altering variants in the 5’UTR of ENG with new insights for the molecular diagnosis of HHT. In silico and functional analysis of ENG 5’UTR variants altering upstream ORFs contributes to the molecular diagnosis of Hereditary Hemorrhagic Telangiectasia and clears the way for the interpretation of this kind of variants in human diseases.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that is characterized by its large heterogeneity in terms of clinical presentation and severity. The pathophysiology of SLE involves an aberrant autoimmune response against various tissues, an excess of apoptotic bodies, and an overproduction of type-I interferon. The genetic contribution to the disease is supported by studies of monozygotic twins, familial clustering, and genome-wide association studies (GWAS) that have identified numerous risk loci. In the early 70s, complement deficiencies led to the description of familial forms of SLE caused by a single gene defect. High-throughput sequencing has recently identified an increasing number of monogenic defects associated with lupus, shaping the concept of monogenic lupus and enhancing our insights into immune tolerance mechanisms. Monogenic lupus (moSLE) should be suspected in patients with either early-onset lupus or syndromic lupus, in male, or in familial cases of lupus. This review discusses the genetic basis of monogenic SLE and proposes its classification based on disrupted pathways. These pathways include defects in the clearance of apoptotic cells or immune complexes, interferonopathies, JAK-STATopathies, TLRopathies, and T and B cell dysregulations.