RESUMEN
The ongoing pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently affecting millions of lives worldwide. Large retrospective studies indicate that an elevated level of inflammatory cytokines and pro-inflammatory factors are associated with both increased disease severity and mortality. Here, using multidimensional epigenetic, transcriptional, in vitro, and in vivo analyses, we report that topoisomerase 1 (TOP1) inhibition suppresses lethal inflammation induced by SARS-CoV-2. Therapeutic treatment with two doses of topotecan (TPT), an FDA-approved TOP1 inhibitor, suppresses infection-induced inflammation in hamsters. TPT treatment as late as 4 days post-infection reduces morbidity and rescues mortality in a transgenic mouse model. These results support the potential of TOP1 inhibition as an effective host-directed therapy against severe SARS-CoV-2 infection. TPT and its derivatives are inexpensive clinical-grade inhibitors available in most countries. Clinical trials are needed to evaluate the efficacy of repurposing TOP1 inhibitors for severe coronavirus disease 2019 (COVID-19) in humans.
Asunto(s)
Tratamiento Farmacológico de COVID-19 , ADN-Topoisomerasas de Tipo I/metabolismo , SARS-CoV-2/metabolismo , Inhibidores de Topoisomerasa I/farmacología , Topotecan/farmacología , Animales , COVID-19/enzimología , COVID-19/patología , Chlorocebus aethiops , Humanos , Inflamación/tratamiento farmacológico , Inflamación/enzimología , Inflamación/patología , Inflamación/virología , Mesocricetus , Ratones , Ratones Transgénicos , Células THP-1 , Células VeroRESUMEN
The nuclear RNA exosome is an essential multi-subunit complex that controls RNA homeostasis. Congenital mutations in RNA exosome genes are associated with neurodegenerative diseases. Little is known about the role of the RNA exosome in the cellular response to pathogens. Here, using NGS and human and mouse genetics, we show that influenza A virus (IAV) ribogenesis and growth are suppressed by impaired RNA exosome activity. Mechanistically, the nuclear RNA exosome coordinates the initial steps of viral transcription with RNAPII at host promoters. The viral polymerase complex co-opts the nuclear RNA exosome complex and cellular RNAs en route to 3' end degradation. Exosome deficiency uncouples chromatin targeting of the viral polymerase complex and the formation of cellular:viral RNA hybrids, which are essential RNA intermediates that license transcription of antisense genomic viral RNAs. Our results suggest that evolutionary arms races have shaped the cellular RNA quality control machinery.
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Interacciones Huésped-Patógeno , Subtipo H1N1 del Virus de la Influenza A/fisiología , Subtipo H3N2 del Virus de la Influenza A/fisiología , Gripe Humana/virología , ARN Polimerasa II/metabolismo , Células A549 , Animales , Inmunoprecipitación de Cromatina , Exorribonucleasas/genética , Complejo Multienzimático de Ribonucleasas del Exosoma/genética , Exosomas/metabolismo , Humanos , Espectrometría de Masas , Ratones , Mutación , Enfermedades Neurodegenerativas/virología , Proteínas de Unión al ARN/genética , Ribosomas/genética , Transcripción GenéticaRESUMEN
Endogenous retroviruses (ERVs) are remnants of ancient parasitic infections and comprise sizable portions of most genomes. Although epigenetic mechanisms silence most ERVs by generating a repressive environment that prevents their expression (heterochromatin), little is known about mechanisms silencing ERVs residing in open regions of the genome (euchromatin). This is particularly important during embryonic development, where induction and repression of distinct classes of ERVs occur in short temporal windows. Here, we demonstrate that transcription-associated RNA degradation by the nuclear RNA exosome and Integrator is a regulatory mechanism that controls the productive transcription of most genes and many ERVs involved in preimplantation development. Disrupting nuclear RNA catabolism promotes dedifferentiation to a totipotent-like state characterized by defects in RNAPII elongation and decreased expression of long genes (gene-length asymmetry). Our results indicate that RNA catabolism is a core regulatory module of gene networks that safeguards RNAPII activity, ERV expression, cell identity, and developmental potency.
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Retrovirus Endógenos , Retrovirus Endógenos/genética , ARN Nuclear , Epigénesis Genética , Heterocromatina , Expresión GénicaRESUMEN
Amyotrophic lateral sclerosis (ALS) is a heterogenous neurodegenerative disorder that affects motor neurons and voluntary muscle control1. ALS heterogeneity includes the age of manifestation, the rate of progression and the anatomical sites of symptom onset. Disease-causing mutations in specific genes have been identified and define different subtypes of ALS1. Although several ALS-associated genes have been shown to affect immune functions2, whether specific immune features account for ALS heterogeneity is poorly understood. Amyotrophic lateral sclerosis-4 (ALS4) is characterized by juvenile onset and slow progression3. Patients with ALS4 show motor difficulties by the time that they are in their thirties, and most of them require devices to assist with walking by their fifties. ALS4 is caused by mutations in the senataxin gene (SETX). Here, using Setx knock-in mice that carry the ALS4-causative L389S mutation, we describe an immunological signature that consists of clonally expanded, terminally differentiated effector memory (TEMRA) CD8 T cells in the central nervous system and the blood of knock-in mice. Increased frequencies of antigen-specific CD8 T cells in knock-in mice mirror the progression of motor neuron disease and correlate with anti-glioma immunity. Furthermore, bone marrow transplantation experiments indicate that the immune system has a key role in ALS4 neurodegeneration. In patients with ALS4, clonally expanded TEMRA CD8 T cells circulate in the peripheral blood. Our results provide evidence of an antigen-specific CD8 T cell response in ALS4, which could be used to unravel disease mechanisms and as a potential biomarker of disease state.
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Esclerosis Amiotrófica Lateral , Linfocitos T CD8-positivos , Células Clonales , Esclerosis Amiotrófica Lateral/inmunología , Esclerosis Amiotrófica Lateral/patología , Animales , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/patología , Células Clonales/patología , ADN Helicasas/genética , ADN Helicasas/metabolismo , Técnicas de Sustitución del Gen , Ratones , Neuronas Motoras/patología , Enzimas Multifuncionales/genética , Enzimas Multifuncionales/metabolismo , Mutación , ARN Helicasas/genética , ARN Helicasas/metabolismoRESUMEN
BACKGROUND: Noninfectious complications are the greatest cause of morbidity and mortality in common variable immunodeficiency (CVID), but their pathogenesis remains poorly defined. OBJECTIVE: Using high-throughput approaches, we aimed to identify, correlate, and determine the significance of immunologic features of CVID with noninfectious complications (CVIDc). METHODS: We simultaneously applied proteomics, RNA sequencing, and mass cytometry to a large cohort with primary antibody deficiency. RESULTS: CVIDc is differentiated from uncomplicated CVID, other forms of primary antibody deficiency, and healthy controls by a distinct plasma proteomic profile. In addition to confirming previously reported elevations of 4-1BB, IL-6, IL-18, and IFN-γ, we found elevations of colony-stimulating factor 1, IL-12p40, IL-18R, oncostatin M, TNF, and vascular endothelial growth factor A to differentiate CVIDc. This cytokine dysregulation correlated with deficiency of LPS-specific antibodies and increased soluble CD14, suggesting microbial translocation. Indicating potential significance of reduced LPS-specific antibodies and resultant microbial-induced inflammation, CVIDc had altered LPS-induced gene expression matching plasma proteomics and corresponding with increased CD14+CD16- monocytes, memory T cells, and tissue inflammation ameliorated by T-cell-targeted therapy. Unsupervised machine learning accurately differentiated subjects with CVIDc and supported cytokine dysregulation, antibody deficit, and T-cell activation as defining and convergent features. CONCLUSIONS: Our data expand understanding of CVIDc proteomics, establish its link with deficiency of IgA and LPS-specific antibodies, and implicate altered LPS-induced gene expression and elevated monocytes and T cells in this cytokine dysregulation. This work indicates that CVIDc results when insufficient antibody neutralization of pathogen-associated molecular patterns, like LPS, occurs in those with a heightened response to these inflammatory mediators, suggesting a 2-hit model of pathogenesis requiring further exploration.
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Inmunodeficiencia Variable Común/inmunología , Citocinas/inmunología , Inmunoglobulinas/deficiencia , Adulto , Células Cultivadas , Inmunodeficiencia Variable Común/sangre , Femenino , Expresión Génica , Humanos , Inmunoglobulinas/sangre , Leucocitos Mononucleares/inmunología , Receptores de Lipopolisacáridos/sangre , Lipopolisacáridos/inmunología , Masculino , Persona de Mediana EdadRESUMEN
BACKGROUND: Classic Kaposi sarcoma (cKS) is an inflammatory tumor caused by human herpesvirus 8 (HHV-8) commonly observed in elderly men of Mediterranean origin. We studied a Finnish family of 5 affected individuals in 2 generations. Except for atypical mycobacterial infection of the index case, the affected individuals did not have notable histories of infection. METHODS: We performed genome and exome sequencing and mapped shared chromosomal regions to identify genetic predisposition in the family. RESULTS: We identified 12 protein-coding candidate variants that segregated in the 3 affected cousins from whom we had samples. The affected mother of the index case was an obligatory carrier. Among the 12 candidates was a rare heterozygous substitution rs141331848 (c.1337C>T, p.Thr446Ile) in the DNA-binding domain of STAT4. The variant was not present in 242 Finnish control genomes or 180 additional regional controls. Activated T-helper cells from the HHV-8-negative variant carriers showed reduced interferon γ production, compared with age and sex matched wild-type individuals. We screened STAT4 in additional 18 familial KS cases and the variant site from 56 sporadic KS cases but detected no pathogenic mutations. CONCLUSIONS: Our data suggest that STAT4 is a potential cKS-predisposition gene, but further functional and genetic validation is needed.
Asunto(s)
Predisposición Genética a la Enfermedad/genética , Factor de Transcripción STAT4/genética , Sarcoma de Kaposi/genética , Anciano , Secuencia de Aminoácidos , Femenino , Ligamiento Genético , Genoma , Humanos , Interferón gamma/inmunología , Leucocitos Mononucleares , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Linaje , Sarcoma de Kaposi/inmunología , Sarcoma de Kaposi/metabolismo , Alineación de Secuencia , Análisis de Secuencia de ADN , Linfocitos TRESUMEN
Germline mutations in FASL and FAS impair Fas-dependent apoptosis and cause recessively or dominantly inherited autoimmune lymphoproliferative syndrome (ALPS). Patients with ALPS typically present with no other clinical phenotype. We investigated a large, consanguineous, multiplex kindred in which biological features of ALPS were found in the context of severe bacterial and viral disease, recurrent hepatopathy and encephalopathy, and cardiac malformations. By a combination of genome-wide linkage and whole-exome sequencing, we identified a homozygous missense mutation in FADD, encoding the Fas-associated death domain protein (FADD), in the patients. This FADD mutation decreases steady-state protein levels and impairs Fas-dependent apoptosis in vitro, accounting for biological ALPS phenotypes in vivo. It also impairs Fas-independent signaling pathways. The observed bacterial infections result partly from functional hyposplenism, and viral infections result from impaired interferon immunity. We describe here a complex clinical disorder, its genetic basis, and some of the key mechanisms underlying its pathogenesis. Our findings highlight the key role of FADD in Fas-dependent and Fas-independent signaling pathways in humans.
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Síndrome Linfoproliferativo Autoinmune/genética , Exones , Proteína de Dominio de Muerte Asociada a Fas/genética , Análisis de Secuencia de ADN , Secuencia de Aminoácidos , Animales , Proteína de Dominio de Muerte Asociada a Fas/química , Femenino , Humanos , Masculino , Datos de Secuencia Molecular , Mutación Missense , Linaje , Homología de Secuencia de AminoácidoAsunto(s)
Síndrome de Inmunodeficiencia con Hiper-IgM Tipo 1/complicaciones , Verrugas/diagnóstico , Verrugas/etiología , Biomarcadores , Biopsia , Análisis Mutacional de ADN , Humanos , Síndrome de Inmunodeficiencia con Hiper-IgM Tipo 1/diagnóstico , Síndrome de Inmunodeficiencia con Hiper-IgM Tipo 1/inmunología , Síndrome de Inmunodeficiencia con Hiper-IgM Tipo 1/terapia , Masculino , Persona de Mediana Edad , Fenotipo , Piel/patologíaRESUMEN
DNMT3A encodes an enzyme that carries out de novo DNA methylation, which is essential for the acquisition of cellular identity and specialized functions during cellular differentiation. DNMT3A is the most frequently mutated gene in age-related clonal hematopoiesis. As such, mature immune cells harboring DNMT3A mutations can be readily detected in elderly persons. Most DNMT3A mutations associated with clonal hematopoiesis are heterozygous and predicted to cause loss of function, indicating that haploinsufficiency is the predominant pathogenic mechanism. Yet, the impact of DNMT3A haploinsufficiency on the function of mature immune cells is poorly understood. Here, we demonstrate that DNMT3A haploinsufficiency impairs the gain of DNA methylation at decommissioned enhancers, while simultaneously and unexpectedly impairing DNA demethylation of newly activated enhancers in mature human myeloid cells. The DNA methylation defects alter the activity of affected enhancers, leading to abnormal gene expression and impaired immune response. These findings provide insights into the mechanism of immune dysfunction associated with clonal hematopoiesis and acquired DNMT3A mutations.
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ADN (Citosina-5-)-Metiltransferasas/genética , Metilación de ADN/genética , Haploinsuficiencia/genética , Sistema Inmunológico/inmunología , Secuencias Reguladoras de Ácidos Nucleicos/genética , Células Cultivadas , ADN (Citosina-5-)-Metiltransferasas/inmunología , Metilación de ADN/inmunología , ADN Metiltransferasa 3A , Expresión Génica/genética , Expresión Génica/inmunología , Haploinsuficiencia/inmunología , Humanos , Mutación/genética , Mutación/inmunología , Secuencias Reguladoras de Ácidos Nucleicos/inmunologíaRESUMEN
The ongoing pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is currently affecting millions of lives worldwide. Large retrospective studies indicate that an elevated level of inflammatory cytokines and pro-inflammatory factors are associated with both increased disease severity and mortality. Here, using multidimensional epigenetic, transcriptional, in vitro and in vivo analyses, we report that Topoisomerase 1 (Top1) inhibition suppresses lethal inflammation induced by SARS-CoV-2. Therapeutic treatment with two doses of Topotecan (TPT), a FDA-approved Top1 inhibitor, suppresses infection-induced inflammation in hamsters. TPT treatment as late as four days post-infection reduces morbidity and rescues mortality in a transgenic mouse model. These results support the potential of Top1 inhibition as an effective host-directed therapy against severe SARS-CoV-2 infection. TPT and its derivatives are inexpensive clinical-grade inhibitors available in most countries. Clinical trials are needed to evaluate the efficacy of repurposing Top1 inhibitors for COVID-19 in humans.
RESUMEN
Viral infection perturbs host cells and can be used to uncover regulatory mechanisms controlling cellular responses and susceptibility to infections. Using cell biological, biochemical, and genetic tools, we reveal that influenza A virus (IAV) infection induces global transcriptional defects at the 3' ends of active host genes and RNA polymerase II (RNAPII) run-through into extragenic regions. Deregulated RNAPII leads to expression of aberrant RNAs (3' extensions and host-gene fusions) that ultimately cause global transcriptional downregulation of physiological transcripts, an effect influencing antiviral response and virulence. This phenomenon occurs with multiple strains of IAV, is dependent on influenza NS1 protein, and can be modulated by SUMOylation of an intrinsically disordered region (IDR) of NS1 expressed by the 1918 pandemic IAV strain. Our data identify a strategy used by IAV to suppress host gene expression and indicate that polymorphisms in IDRs of viral proteins can affect the outcome of an infection.
Asunto(s)
Gripe Humana/genética , ARN Polimerasa II/genética , Regiones Terminadoras Genéticas/genética , Humanos , Virus de la Influenza A/patogenicidad , Virus de la Influenza A/fisiología , VirulenciaRESUMEN
BACKGROUND: Myocarditis is inflammation of the heart muscle that can follow various viral infections. Why children only rarely develop life-threatening acute viral myocarditis (AVM), given that the causal viral infections are common, is unknown. Genetic lesions might underlie such susceptibilities. Mouse genetic studies demonstrated that interferon (IFN)-α/ß immunity defects increased susceptibility to virus-induced myocarditis. Moreover, variations in human TLR3, a potent inducer of IFNs, were proposed to underlie AVM. OBJECTIVES: This study sought to evaluate the hypothesis that human genetic factors may underlie AVM in previously healthy children. METHODS: We tested the role of TLR3-IFN immunity using human induced pluripotent stem cell-derived cardiomyocytes. We then performed whole-exome sequencing of 42 unrelated children with acute myocarditis (AM), some with proven viral causes. RESULTS: We found that TLR3- and STAT1-deficient cardiomyocytes were not more susceptible to Coxsackie virus B3 (CVB3) infection than control cells. Moreover, CVB3 did not induce IFN-α/ß and IFN-α/ß-stimulated genes in control cardiomyocytes. Finally, exogenous IFN-α did not substantially protect cardiomyocytes against CVB3. We did not observe a significant enrichment of rare variations in TLR3- or IFN-α/ß-related genes. Surprisingly, we found that homozygous but not heterozygous rare variants in genes associated with inherited cardiomyopathies were significantly enriched in AM-AVM patients compared with healthy individuals (p = 2.22E-03) or patients with other diseases (p = 1.08E-04). Seven of 42 patients (16.7%) carried rare biallelic (homozygous or compound heterozygous) nonsynonymous or splice-site variations in 6 cardiomyopathy-associated genes (BAG3, DSP, PKP2, RYR2, SCN5A, or TNNI3). CONCLUSIONS: Previously silent recessive defects of the myocardium may predispose to acute heart failure presenting as AM, notably after common viral infections in children.
Asunto(s)
Cardiomiopatías/genética , Enterovirus Humano B/fisiología , Miocarditis/genética , Factor de Transcripción STAT1/genética , Receptor Toll-Like 3/genética , Cardiomiopatías/complicaciones , Estudios de Casos y Controles , Femenino , Interacciones Huésped-Patógeno/genética , Humanos , Células Madre Pluripotentes Inducidas , Masculino , Miocarditis/virología , Miocitos Cardíacos/virologíaRESUMEN
OBJECTIVE: To determine the proportion of children with herpes simplex encephalitis (HSE) displaying TLR3 deficiency, the extent of TLR3 allelic heterogeneity, and the specific clinical features of TLR3 deficiency. METHODS: We determined the sequence of all exons of TLR3 in 110 of the 120 patients with HSE enrolled in our study who do not carry any of the previously described HSE-predisposing mutations of TLR3 pathway genes (TLR3, UNC93B1, TRIF, TRAF3, and TBK1). All the new mutant TLR3 alleles detected were characterized experimentally in-depth to establish the causal relationship between the genotype and phenotype. RESULTS: In addition to the 3 previously reported TLR3-deficient patients from the same cohort, 6 other children or young adults with HSE carry 1 of 5 unique or extremely rare (minor allele frequency <0.001) missense TLR3 alleles. Two alleles (M374T, D592N) heterozygous in 3 patients are not deleterious in vitro. The other 3 are deleterious via different mechanisms: G743D+R811I and L360P heterozygous in 2 patients are loss-of-function due to low levels of expression and lack of cleavage, respectively, and R867Q homozygous in 1 patient is hypomorphic. The 3 patients' fibroblasts display impaired TLR3 responses and enhanced herpes simplex virus 1 susceptibility. Overall, TLR3 deficiency is therefore found in 6 (5%) of the 120 patients studied. There is high allelic heterogeneity, with 3 forms of autosomal dominant partial defect by negative dominance or haploinsufficiency, and 2 forms of autosomal recessive defect with complete or partial deficiency. Finally, 4 (66%) of the 6 TLR3-deficient patients had at least 1 late relapse of HSE, whereas relapse occurred in only 12 (10%) of the total cohort of 120 patients. CONCLUSIONS: Childhood-onset HSE is due to TLR3 deficiency in a traceable fraction of patients, in particular the ones with HSE recurrence. Mutations in TLR3 and TLR3 pathway genes should be searched and experimentally studied in children with HSE, and patients with proven TLR3 deficiency should be followed carefully.
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Encefalitis por Herpes Simple/diagnóstico , Encefalitis por Herpes Simple/genética , Frecuencia de los Genes/genética , Mutación/genética , Receptor Toll-Like 3/deficiencia , Receptor Toll-Like 3/genética , Adolescente , Células Cultivadas , Niño , Preescolar , Femenino , Humanos , Lactante , Masculino , Linaje , Recurrencia , Factores de RiesgoAsunto(s)
Enfermedad de Castleman/diagnóstico , Receptor fas/metabolismo , Adulto , Secuencia de Aminoácidos , Animales , Línea Celular , Membrana Celular/metabolismo , Proteína Ligando Fas/metabolismo , Humanos , Masculino , Linaje , Polimorfismo de Nucleótido Simple , Unión Proteica , Alineación de Secuencia , Receptor fas/genéticaRESUMEN
Kaposi sarcoma (KS), a human herpes virus 8 (HHV-8; also called KSHV)-induced endothelial tumor, develops only in a small fraction of individuals infected with HHV-8. We hypothesized that inborn errors of immunity to HHV-8 might underlie the exceedingly rare development of classic KS in childhood. We report here autosomal recessive OX40 deficiency in an otherwise healthy adult with childhood-onset classic KS. OX40 is a co-stimulatory receptor expressed on activated T cells. Its ligand, OX40L, is expressed on various cell types, including endothelial cells. We found OX40L was abundantly expressed in KS lesions. The mutant OX40 protein was poorly expressed on the cell surface and failed to bind OX40L, resulting in complete functional OX40 deficiency. The patient had a low proportion of effector memory CD4(+) T cells in the peripheral blood, consistent with impaired CD4(+) T cell responses to recall antigens in vitro. The proportion of effector memory CD8(+) T cells was less diminished. The proportion of circulating memory B cells was low, but the antibody response in vivo was intact, including the response to a vaccine boost. Together, these findings suggest that human OX40 is necessary for robust CD4(+) T cell memory and confers apparently selective protective immunity against HHV-8 infection in endothelial cells.
Asunto(s)
Patrón de Herencia/genética , Receptores OX40/deficiencia , Receptores OX40/genética , Sarcoma de Kaposi/genética , Adulto , Edad de Inicio , Secuencia de Aminoácidos , Sustitución de Aminoácidos/genética , Formación de Anticuerpos/inmunología , Secuencia de Bases , Membrana Celular/metabolismo , Niño , Cisteína/genética , Femenino , Células HEK293 , Homocigoto , Humanos , Memoria Inmunológica/inmunología , Espacio Intracelular/metabolismo , Recuento de Linfocitos , Datos de Secuencia Molecular , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Mutación/genética , Receptores OX40/química , Receptores OX40/metabolismo , Sarcoma de Kaposi/sangre , Sarcoma de Kaposi/inmunología , Sarcoma de Kaposi/patología , Subgrupos de Linfocitos T/metabolismo , Adulto JovenRESUMEN
Isolated congenital asplenia (ICA) is characterized by the absence of a spleen at birth in individuals with no other developmental defects. The patients are prone to life-threatening bacterial infections. The unbiased analysis of exomes revealed heterozygous mutations in RPSA in 18 patients from eight kindreds, corresponding to more than half the patients and over one-third of the kindreds studied. The clinical penetrance in these kindreds is complete. Expression studies indicated that the mutations carried by the patients-a nonsense mutation, a frameshift duplication, and five different missense mutations-cause autosomal dominant ICA by haploinsufficiency. RPSA encodes ribosomal protein SA, a component of the small subunit of the ribosome. This discovery establishes an essential role for RPSA in human spleen development.
Asunto(s)
Haploinsuficiencia , Síndrome de Heterotaxia/genética , Receptores de Laminina/genética , Proteínas Ribosómicas/genética , Bazo/anomalías , Análisis Mutacional de ADN , Sitios Genéticos , Humanos , Mutación , Linaje , Penetrancia , Bazo/crecimiento & desarrolloRESUMEN
Infection with human herpesvirus 8 (HHV-8), the etiological agent of Kaposi's sarcoma, has been shown to display strong familial aggregation, in countries in which HHV-8 infection is endemic. We investigated 40 large families (608 subjects aged one to 88 years) living in an isolated area of Cameroon in which HHV-8 is highly endemic. We performed a two-step genetic analysis for HHV-8 infection status (HHV-8+/HHV-8- determined by immunofluorescence) consisting of an initial segregation analysis followed by a model-based genome-wide linkage analysis. Overall HHV-8 seroprevalence was 60%, increasing with age. Segregation analysis provided strong evidence for a recessive major gene conferring predisposition to HHV-8 infection. This gene is predicted to have a major effect during childhood, with almost all homozygous predisposed subjects (â¼7% of the population) becoming infected by the age of 10. Linkage analysis was carried out on the 15 most informative families, corresponding to 205 genotyped subjects. A single region on chromosome 3p22 was significantly linked to HHV-8 infection (LOD score=3.83, P=2.0 × 10(-5)). This study provides the first evidence that HHV-8 infection in children in endemic areas has a strong genetic basis involving at least one recessive major locus on chromosome 3p22.
Asunto(s)
Cromosomas Humanos Par 3/genética , Predisposición Genética a la Enfermedad , Infecciones por Herpesviridae/genética , Infecciones por Herpesviridae/virología , Herpesvirus Humano 8/patogenicidad , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Anticuerpos Antivirales/inmunología , Camerún , Niño , Preescolar , Familia , Femenino , Genes Recesivos , Infecciones por Herpesviridae/transmisión , Herpesvirus Humano 8/inmunología , Humanos , Lactante , Masculino , Persona de Mediana Edad , Estudios SeroepidemiológicosRESUMEN
We investigated two siblings with granulomatous histiocytosis prominent in the nasal area, mimicking rhinoscleroma and Rosai-Dorfman syndrome. Genome-wide linkage analysis and whole-exome sequencing identified a homozygous frameshift deletion in SLC29A3, which encodes human equilibrative nucleoside transporter-3 (hENT3). Germline mutations in SLC29A3 have been reported in rare patients with a wide range of overlapping clinical features and inherited disorders including H syndrome, pigmented hypertrichosis with insulin-dependent diabetes, and Faisalabad histiocytosis. With the exception of insulin-dependent diabetes and mild finger and toe contractures in one sibling, the two patients with nasal granulomatous histiocytosis studied here displayed none of the many SLC29A3-associated phenotypes. This mild clinical phenotype probably results from a remarkable genetic mechanism. The SLC29A3 frameshift deletion prevents the expression of the normally coding transcripts. It instead leads to the translation, expression, and function of an otherwise noncoding, out-of-frame mRNA splice variant lacking exon 3 that is eliminated by nonsense-mediated mRNA decay (NMD) in healthy individuals. The mutated isoform differs from the wild-type hENT3 by the modification of 20 residues in exon 2 and the removal of another 28 amino acids in exon 3, which include the second transmembrane domain. As a result, this new isoform displays some functional activity. This mechanism probably accounts for the narrow and mild clinical phenotype of the patients. This study highlights the 'rescue' role played by a normally noncoding mRNA splice variant of SLC29A3, uncovering a new mechanism by which frameshift mutations can be hypomorphic.
Asunto(s)
Mutación del Sistema de Lectura , Histiocitosis/genética , Enfermedades Nasales/genética , Proteínas de Transporte de Nucleósidos/genética , ARN no Traducido/genética , Eliminación de Secuencia , Adulto , Femenino , Mutación del Sistema de Lectura/genética , Humanos , Masculino , Linaje , Fenotipo , Biosíntesis de Proteínas/genética , Isoformas de ARN/genética , Sitios de Empalme de ARN/genética , Índice de Severidad de la Enfermedad , Hermanos , Adulto JovenRESUMEN
Childhood multicentric Castleman disease (MCD) is a rare and unexplained lymphoproliferative disorder. We report a human herpesvirus-8 (HHV-8)-infected child, born to consanguineous Comorian parents, who displayed isolated MCD in the absence of any known immunodeficiency. We also systematically review the clinical features of the 32 children previously reported with isolated and unexplained MCD. The characteristics of this patient and the geographic areas of origin of most previous cases suggest that pediatric MCD is associated with HHV-8 infection. Moreover, as previously suggested for Kaposi sarcoma, MCD in childhood may result from inborn errors of immunity to HHV-8 infection.