High number of candidate gene variants are identified as disease-causing in a period of 4 years.

Advances in bioinformatic tools paired with the ongoing accumulation of genetic knowledge and periodic reanalysis of genomic sequencing data have led to an improvement in genetic diagnostic rates. Candidate gene variants (CGVs) identified during sequencing or on reanalysis but not yet implicated in human disease or associated with a phenotypically distinct condition are often not revisited, leading to missed diagnostic opportunities. Here, we revisited 33 such CGVs from our previously published study and determined that 16 of them are indeed disease-causing (novel or phenotype expansion) since their identification. These results emphasize the need to focus on previously identified CGVs during sequencing or reanalysis and the importance of sharing that information with researchers around the world, including relevant functional analysis to establish disease causality.

Atypical Localization of Eczema Discriminates DOCK8 or STAT3 Deficiencies from Atopic Dermatitis.

PURPOSE: Autosomal recessive dedicator of cytokinesis 8 (DOCK8-/-) and autosomal dominant signal transducer and activator of transcription 3 (STAT3-/+) deficiencies are inborn errors of immunity (IEI) disorders present with the classic features of eczema and create a dilemma during differentiation from atopic dermatitis (AD). Therefore, an appropriate approach is required for eczema to diagnose DOCK8-/- and STAT3-/+ early. Here, we described a set of clinical and immunological variables, including atypical AD localizations and lymphocyte subsets, to differentiate DOCK8-/- or STAT3-/+ from AD. METHODS: This multicenter study involved 100 patients with DOCK8-/- and STAT3-/+ and moderate/severe AD. We recruited disease manifestations, including detailed localizations of eczema, infections, and allergy. Principle component analysis (PCA) was used to discriminate DOCK8-/- or STAT3-/+ from AD. RESULTS: There were 43 patients with DOCK8-/-, 23 with STAT3-/+, and 34 with AD. Pneumonia, severe infections, mucocutaneous candidiasis, and skin abscesses were commonly observed in DOCK8 and STAT3 deficiencies. Atypical skin involvement with neonatal rash, retro auricular, axillary, sacral, and genital eczema discriminate DOCK8-/- and STAT3-/+ from AD with high specificity ranges between 73.5 and 94.1% and positive predictive index ranges between 55 and 93.1%. Together with using absolute numbers of CD3+, CD4+, and CD8+ T cells, the combined clinical and laboratory features showed perfect differentiation between DOCK8-/- or STAT3-/+ and AD via PCA. CONCLUSIONS: The described features can be easily implemented by physicians providing early diagnosis of DOCK8 and STAT3 deficiencies.

Integrated multi-omics approach reveals the role of SPEG in skeletal muscle biology including its relationship with myospryn complex.

Autosomal-recessive mutations in SPEG (striated muscle preferentially expressed protein kinase) have been linked to centronuclear myopathy. Loss of SPEG is associated with defective triad formation, abnormal excitation-contraction coupling, and calcium mishandling in skeletal muscles. To elucidate the underlying molecular pathways, we have utilized multi-omics tools and analysis to obtain a comprehensive view of the complex biological processes. We identified that SPEG interacts with myospryn complex proteins (CMYA5, FSD2, RyR1), and SPEG deficiency results in myospryn complex abnormalities. In addition, transcriptional and protein profiles of SPEG-deficient muscle revealed defective mitochondrial function including aberrant accumulation of enlarged mitochondria on electron microscopy. Furthermore, SPEG regulates RyR1 phosphorylation at S2902, and its loss affects JPH2 phosphorylation at multiple sites. On analyzing the transcriptome, the most dysregulated pathways affected by SPEG deficiency included extracellular matrix-receptor interaction and peroxisome proliferator-activated receptors signaling, which may be due to defective triad and mitochondrial abnormalities. In summary, we have elucidated the critical role of SPEG in triad as it works closely with myospryn complex, phosphorylates JPH2 and RyR1, and demonstrated that its deficiency is associated with mitochondrial abnormalities. This study emphasizes the importance of using multi-omics techniques to comprehensively analyze the molecular anomalies of rare diseases. Synopsis: We have previously linked mutations in SPEG (striated preferentially expressed protein) with a recessive form of centronuclear myopathy and/or dilated cardiomyopathy and have characterized a striated muscle-specific SPEG-deficient mouse model that recapitulates human disease with disruption of the triad structure and calcium homeostasis in skeletal muscles. In this study, we applied multi-omics approaches (interactomic, proteomic, phosphoproteomic, and transcriptomic analyses) in the skeletal muscles of SPEG-deficient mice to assess the underlying pathways associated with the pathological and molecular abnormalities. SPEG interacts with myospryn complex proteins (CMYA5, FSD2, RyR1), and its deficiency results in myospryn complex abnormalities.SPEG regulates RyR1 phosphorylation at S2902, and its loss affects JPH2 phosphorylation at multiple sites.SPEGα and SPEGß have different interacting partners suggestive of differential function.Transcriptome analysis indicates dysregulated pathways of ECM-receptor interaction and peroxisome proliferator-activated receptor signaling.Mitochondrial defects on the transcriptome, proteome, and electron microscopy, may be a consequence of defective calcium signaling.

An intronic variant in TBX4 in a single family with variable and severe pulmonary manifestations.

A male infant presented at term with neonatal respiratory failure and pulmonary hypertension. His respiratory symptoms improved initially, but he exhibited a biphasic clinical course, re-presenting at 15 months of age with tachypnea, interstitial lung disease, and progressive pulmonary hypertension. We identified an intronic TBX4 gene variant in close proximity to the canonical donor splice site of exon 3 (hg 19; chr17:59543302; c.401 + 3 A > T), also carried by his father who had a typical TBX4-associated skeletal phenotype and mild pulmonary hypertension, and by his deceased sister who died shortly after birth of acinar dysplasia. Analysis of patient-derived cells demonstrated a significant reduction in TBX4 expression resulting from this intronic variant. Our study illustrates the variable expressivity in cardiopulmonary phenotype conferred by TBX4 mutation and the utility of genetic diagnostics in enabling accurate identification and classification of more subtly affected family members.

Severe allergic dysregulation due to a gain of function mutation in the transcription factor STAT6.

BACKGROUND: Inborn errors of immunity have been implicated in causing immune dysregulation, including allergic diseases. STAT6 is a key regulator of allergic responses. OBJECTIVES: This study sought to characterize a novel gain-of-function STAT6 mutation identified in a child with severe allergic manifestations. METHODS: Whole-exome and targeted gene sequencing, lymphocyte characterization, and molecular and functional analyses of mutated STAT6 were performed. RESULTS: This study reports a child with a missense mutation in the DNA binding domain of STAT6 (c.1114G>A, p.E372K) who presented with severe atopic dermatitis, eosinophilia, and elevated IgE. Naive lymphocytes from the affected patient displayed increased TH2- and suppressed TH1- and TH17-cell responses. The mutation augmented both basal and cytokine-induced STAT6 phosphorylation without affecting dephosphorylation kinetics. Treatment with the Janus kinase 1/2 inhibitor ruxolitinib reversed STAT6 hyperresponsiveness to IL-4, normalized TH1 and TH17 cells, suppressed the eosinophilia, and improved the patient's atopic dermatitis. CONCLUSIONS: This study identified a novel inborn error of immunity due to a STAT6 gain-of-function mutation that gave rise to severe allergic dysregulation. Janus kinase inhibitor therapy could represent an effective targeted treatment for this disorder.

Reanalysis of clinical exome identifies the second variant in two individuals with recessive disorders.

Clinical exome/genome sequencing is increasingly being utilized by clinicians to diagnose various likely genetic conditions, but many cases remain undiagnosed. In a subset of those undiagnosed cases, a single heterozygous variant in an autosomal recessive (AR) condition with consistent phenotype may be identified, raising the question if a second variant is missing. Here, we report two cases of recessive conditions in which only one heterozygous variant was initially reported by clinical exome sequencing, and on research reanalysis a second heterozygous variant in trans was identified. We performed a review of the existing exome reanalysis literature and found that this aspect is often not emphasized. These findings highlight the importance of data reanalysis in undiagnosed cases where only a single disease-associated variant is identified in an AR condition with a strong link to presenting phenotype.

The Notch1/CD22 signaling axis disrupts Treg function in SARS-CoV-2-associated multisystem inflammatory syndrome in children.

Multisystem inflammatory syndrome in children (MIS-C) evolves in some pediatric patients following acute infection with SARS-CoV-2 by hitherto unknown mechanisms. Whereas acute-COVID-19 severity and outcomes were previously correlated with Notch4 expression on Tregs, here, we show that Tregs in MIS-C were destabilized through a Notch1-dependent mechanism. Genetic analysis revealed that patients with MIS-C had enrichment of rare deleterious variants affecting inflammation and autoimmunity pathways, including dominant-negative mutations in the Notch1 regulators NUMB and NUMBL leading to Notch1 upregulation. Notch1 signaling in Tregs induced CD22, leading to their destabilization in a mTORC1-dependent manner and to the promotion of systemic inflammation. These results identify a Notch1/CD22 signaling axis that disrupts Treg function in MIS-C and point to distinct immune checkpoints controlled by individual Treg Notch receptors that shape the inflammatory outcome in SARS-CoV-2 infection.

A Stk4-Foxp3-NF-κB p65 transcriptional complex promotes Treg cell activation and homeostasis.

The molecular programs involved in regulatory T (Treg) cell activation and homeostasis remain incompletely understood. Here, we show that T cell receptor (TCR) signaling in Treg cells induces the nuclear translocation of serine/threonine kinase 4 (Stk4), leading to the formation of an Stk4-NF-κB p65-Foxp3 complex that regulates Foxp3- and p65-dependent transcriptional programs. This complex was stabilized by Stk4-dependent phosphorylation of Foxp3 on serine-418. Stk4 deficiency in Treg cells, either alone or in combination with its homolog Stk3, precipitated a fatal autoimmune lymphoproliferative disease in mice characterized by decreased Treg cell p65 expression and nuclear translocation, impaired NF-κB p65-Foxp3 complex formation, and defective Treg cell activation. In an adoptive immunotherapy model, overexpression of p65 or the phosphomimetic Foxp3S418E in Stk3/4-deficient Treg cells ameliorated their immune regulatory defects. Our studies identify Stk4 as an essential TCR-responsive regulator of p65-Foxp3-dependent transcription that promotes Treg cell-mediated immune tolerance.

Notch1-CD22-Dependent Immune Dysregulation in the SARS-CoV2-Associated Multisystem Inflammatory Syndrome in Children.

Multisystem inflammatory syndrome in children (MIS-C) evolves in some pediatric patients following acute infection with SARS-CoV-2 by hitherto unknown mechanisms. Whereas acute-COVID-19 severity and outcome were previously correlated with Notch4 expression on regulatory T (Treg) cells, here we show that the Treg cells in MIS-C are destabilized in association with increased Notch1 expression. Genetic analysis revealed that MIS-C patients were enriched in rare deleterious variant impacting inflammation and autoimmunity pathways, including dominant negative mutations in the Notch1 regulators NUMB and NUMBL. Notch1 signaling in Treg cells induced CD22, leading to their destabilization in an mTORC1 dependent manner and to the promotion of systemic inflammation. These results establish a Notch1-CD22 signaling axis that disrupts Treg cell function in MIS-C and point to distinct immune checkpoints controlled by individual Treg cell Notch receptors that shape the inflammatory outcome in SARS-CoV-2 infection.

Congenital X-linked neutropenia with myelodysplasia and somatic tetraploidy due to a germline mutation in SEPT6.

Septins play key roles in mammalian cell division and cytokinesis but have not previously been implicated in a germline human disorder. A male infant with severe neutropenia and progressive dysmyelopoiesis with tetraploid myeloid precursors was identified. No known genetic etiologies for neutropenia or bone marrow failure were found. However, next-generation sequencing of germline samples from the patient revealed a novel, de novo germline stop-loss mutation in the X-linked gene SEPT6 that resulted in reduced SEPT6 staining in bone marrow granulocyte precursors and megakaryocytes. Patient skin fibroblast-derived induced pluripotent stem cells (iPSCs) produced reduced myeloid colonies, particularly of the granulocyte lineage. CRISPR/Cas9 knock-in of the patient's mutation or complete knock-out of SEPT6 was not tolerated in non-patient-derived iPSCs or human myeloid cell lines, but SEPT6 knock-out was successful in an erythroid cell line and resulting clones revealed a propensity to multinucleation. In silico analysis predicts that the mutated protein hinders the dimerization of SEPT6 coiled-coils in both parallel and antiparallel arrangements, which could in turn impair filament formation. These data demonstrate a critical role for SEPT6 in chromosomal segregation in myeloid progenitors that can account for the unusual predisposition to aneuploidy and dysmyelopoiesis.

Evolution and long-term outcomes of combined immunodeficiency due to CARMIL2 deficiency.

BACKGROUND: Biallelic loss-of-function mutations in CARMIL2 cause combined immunodeficiency associated with dermatitis, inflammatory bowel disease (IBD), and EBV-related smooth muscle tumors. Clinical and immunological characterizations of the disease with long-term follow-up and treatment options have not been previously reported in large cohorts. We sought to determine the clinical and immunological features of CARMIL2 deficiency and long-term efficacy of treatment in controlling different disease manifestations. METHODS: The presenting phenotypes, long-term outcomes, and treatment responses were evaluated prospectively in 15 CARMIL2-deficient patients, including 13 novel cases. Lymphocyte subpopulations, protein expression, regulatory T (Treg), and circulating T follicular helper (cTFH ) cells were analyzed. Three-dimensional (3D) migration assay was performed to determine T-cell shape. RESULTS: Mean age at disease onset was 38 ± 23 months. Main clinical features were skin manifestations (n = 14, 93%), failure to thrive (n = 10, 67%), recurrent infections (n = 10, 67%), allergic symptoms (n = 8, 53%), chronic diarrhea (n = 4, 27%), and EBV-related leiomyoma (n = 2, 13%). Skin manifestations ranged from atopic and seborrheic dermatitis to psoriasiform rash. Patients had reduced proportions of memory CD4+ T cells, Treg, and cTFH cells. Memory B and NK cells were also decreased. CARMIL2-deficient T cells exhibited reduced T-cell proliferation and cytokine production following CD28 co-stimulation and normal morphology when migrating in a high-density 3D collagen gel matrix. IBD was the most severe clinical manifestation, leading to growth retardation, requiring multiple interventional treatments. All patients were alive with a median follow-up of 10.8 years (range: 3-17 years). CONCLUSION: This cohort provides clinical and immunological features and long-term follow-up of different manifestations of CARMIL2 deficiency.

Reanalysis of Exome Data Identifies Novel SLC25A46 Variants Associated with Leigh Syndrome.

SLC25A46 (solute carrier family 25 member 46) mutations have been linked to various neurological diseases with recessive inheritance, including Leigh syndrome, optic atrophy, and lethal congenital pontocerebellar hypoplasia. SLC25A46 is expressed in the outer membrane of mitochondria, where it plays a critical role in mitochondrial dynamics. A deceased 7-month-old female infant was suspected to have Leigh syndrome. Clinical exome sequencing was non-diagnostic, but research reanalysis of the sequencing data identified two novel variants in SLC25A46: a missense (c.1039C>T, p.Arg347Cys; NM_138773, hg19) and a donor splice region variant (c.283+5G>A) in intron 1. Both variants were predicted to be damaging. Sanger sequencing of cDNA detected a single missense allele in the patient compared to control, and the SLC25A46 transcript levels were also reduced due to the splice region variant. Additionally, Western blot analysis of whole-cell lysate showed a decrease of SLC25A46 expression in proband fibroblasts, relative to control cells. Further, analysis of mitochondrial morphology revealed evidence of increased fragmentation of the mitochondrial network in proband fibroblasts, compared to control cells. Collectively, our findings suggest that these novel variants in SLC24A46, the donor splice one and the missense variant, are the cause of the neurological phenotype in this proband.

A data-driven architecture using natural language processing to improve phenotyping efficiency and accelerate genetic diagnoses of rare disorders.

Effective genetic diagnosis requires the correlation of genetic variant data with detailed phenotypic information. However, manual encoding of clinical data into machine-readable forms is laborious and subject to observer bias. Natural language processing (NLP) of electronic health records has great potential to enhance reproducibility at scale but suffers from idiosyncrasies in physician notes and other medical records. We developed methods to optimize NLP outputs for automated diagnosis. We filtered NLP-extracted Human Phenotype Ontology (HPO) terms to more closely resemble manually extracted terms and identified filter parameters across a three-dimensional space for optimal gene prioritization. We then developed a tiered pipeline that reduces manual effort by prioritizing smaller subsets of genes to consider for genetic diagnosis. Our filtering pipeline enabled NLP-based extraction of HPO terms to serve as a sufficient replacement for manual extraction in 92% of prospectively evaluated cases. In 75% of cases, the correct causal gene was ranked higher with our applied filters than without any filters. We describe a framework that can maximize the utility of NLP-based phenotype extraction for gene prioritization and diagnosis. The framework is implemented within a cloud-based modular architecture that can be deployed across health and research institutions.

A homozygous stop-gain variant in ARHGAP42 is associated with childhood interstitial lung disease, systemic hypertension, and immunological findings.

ARHGAP42 encodes Rho GTPase activating protein 42 that belongs to a member of the GTPase Regulator Associated with Focal Adhesion Kinase (GRAF) family. ARHGAP42 is involved in blood pressure control by regulating vascular tone. Despite these findings, disorders of human variants in the coding part of ARHGAP42 have not been reported. Here, we describe an 8-year-old girl with childhood interstitial lung disease (chILD), systemic hypertension, and immunological findings who carries a homozygous stop-gain variant (c.469G>T, p.(Glu157Ter)) in the ARHGAP42 gene. The family history is notable for both parents with hypertension. Histopathological examination of the proband lung biopsy showed increased mural smooth muscle in small airways and alveolar septa, and concentric medial hypertrophy in pulmonary arteries. ARHGAP42 stop-gain variant in the proband leads to exon 5 skipping, and reduced ARHGAP42 levels, which was associated with enhanced RhoA and Cdc42 expression. This is the first report linking a homozygous stop-gain variant in ARHGAP42 with a chILD disorder, systemic hypertension, and immunological findings in human patient. Evidence of smooth muscle hypertrophy on lung biopsy and an increase in RhoA/ROCK signaling in patient cells suggests the potential mechanistic link between ARHGAP42 deficiency and the development of chILD disorder.

Unique variants in CLCN3, encoding an endosomal anion/proton exchanger, underlie a spectrum of neurodevelopmental disorders.

The genetic causes of global developmental delay (GDD) and intellectual disability (ID) are diverse and include variants in numerous ion channels and transporters. Loss-of-function variants in all five endosomal/lysosomal members of the CLC family of Cl- channels and Cl-/H+ exchangers lead to pathology in mice, humans, or both. We have identified nine variants in CLCN3, the gene encoding CIC-3, in 11 individuals with GDD/ID and neurodevelopmental disorders of varying severity. In addition to a homozygous frameshift variant in two siblings, we identified eight different heterozygous de novo missense variants. All have GDD/ID, mood or behavioral disorders, and dysmorphic features; 9/11 have structural brain abnormalities; and 6/11 have seizures. The homozygous variants are predicted to cause loss of ClC-3 function, resulting in severe neurological disease similar to the phenotype observed in Clcn3-/- mice. Their MRIs show possible neurodegeneration with thin corpora callosa and decreased white matter volumes. Individuals with heterozygous variants had a range of neurodevelopmental anomalies including agenesis of the corpus callosum, pons hypoplasia, and increased gyral folding. To characterize the altered function of the exchanger, electrophysiological analyses were performed in Xenopus oocytes and mammalian cells. Two variants, p.Ile607Thr and p.Thr570Ile, had increased currents at negative cytoplasmic voltages and loss of inhibition by luminal acidic pH. In contrast, two other variants showed no significant difference in the current properties. Overall, our work establishes a role for CLCN3 in human neurodevelopment and shows that both homozygous loss of ClC-3 and heterozygous variants can lead to GDD/ID and neuroanatomical abnormalities.

Author Correction: A regulatory T cell Notch4-GDF15 axis licenses tissue inflammation in asthma.

A Correction to this paper has been published: https://doi.org/10.1038/s41590-021-00929-x.

Notch4 signaling limits regulatory T-cell-mediated tissue repair and promotes severe lung inflammation in viral infections.

A cardinal feature of COVID-19 is lung inflammation and respiratory failure. In a prospective multi-country cohort of COVID-19 patients, we found that increased Notch4 expression on circulating regulatory T (Treg) cells was associated with disease severity, predicted mortality, and declined upon recovery. Deletion of Notch4 in Treg cells or therapy with anti-Notch4 antibodies in conventional and humanized mice normalized the dysregulated innate immunity and rescued disease morbidity and mortality induced by a synthetic analog of viral RNA or by influenza H1N1 virus. Mechanistically, Notch4 suppressed the induction by interleukin-18 of amphiregulin, a cytokine necessary for tissue repair. Protection by Notch4 inhibition was recapitulated by therapy with Amphiregulin and, reciprocally, abrogated by its antagonism. Amphiregulin declined in COVID-19 subjects as a function of disease severity and Notch4 expression. Thus, Notch4 expression on Treg cells dynamically restrains amphiregulin-dependent tissue repair to promote severe lung inflammation, with therapeutic implications for COVID-19 and related infections.

A regulatory T cell Notch4-GDF15 axis licenses tissue inflammation in asthma.

Elucidating the mechanisms that sustain asthmatic inflammation is critical for precision therapies. We found that interleukin-6- and STAT3 transcription factor-dependent upregulation of Notch4 receptor on lung tissue regulatory T (Treg) cells is necessary for allergens and particulate matter pollutants to promote airway inflammation. Notch4 subverted Treg cells into the type 2 and type 17 helper (TH2 and TH17) effector T cells by Wnt and Hippo pathway-dependent mechanisms. Wnt activation induced growth and differentiation factor 15 expression in Treg cells, which activated group 2 innate lymphoid cells to provide a feed-forward mechanism for aggravated inflammation. Notch4, Wnt and Hippo were upregulated in circulating Treg cells of individuals with asthma as a function of disease severity, in association with reduced Treg cell-mediated suppression. Our studies thus identify Notch4-mediated immune tolerance subversion as a fundamental mechanism that licenses tissue inflammation in asthma.

Homozygous deletions implicate non-coding epigenetic marks in Autism spectrum disorder.

More than 98% of the human genome is made up of non-coding DNA, but techniques to ascertain its contribution to human disease have lagged far behind our understanding of protein coding variations. Autism spectrum disorder (ASD) has been mostly associated with coding variations via de novo single nucleotide variants (SNVs), recessive/homozygous SNVs, or de novo copy number variants (CNVs); however, most ASD cases continue to lack a genetic diagnosis. We analyzed 187 consanguineous ASD families for biallelic CNVs. Recessive deletions were significantly enriched in affected individuals relative to their unaffected siblings (17% versus 4%, p < 0.001). Only a small subset of biallelic deletions were predicted to result in coding exon disruption. In contrast, biallelic deletions in individuals with ASD were enriched for overlap with regulatory regions, with 23/28 CNVs disrupting histone peaks in ENCODE (p < 0.009). Overlap with regulatory regions was further demonstrated by comparisons to the 127-epigenome dataset released by the Roadmap Epigenomics project, with enrichment for enhancers found in primary brain tissue and neuronal progenitor cells. Our results suggest a novel noncoding mechanism of ASD, describe a powerful method to identify important noncoding regions in the human genome, and emphasize the potential significance of gene activation and regulation in cognitive and social function.