RESUMEN
While it is widely thought that de novo mutations (DNMs) occur randomly, we previously showed that some DNMs are enriched because they are positively selected in the testes of aging men. These "selfish" mutations cause disorders with a shared presentation of features, including exclusive paternal origin, significant increase of the father's age, and high apparent germline mutation rate. To date, all known selfish mutations cluster within the components of the RTK-RAS-MAPK signaling pathway, a critical modulator of testicular homeostasis. Here, we demonstrate the selfish nature of the SMAD4 DNMs causing Myhre syndrome (MYHRS). By analyzing 16 informative trios, we show that MYHRS-causing DNMs originated on the paternally derived allele in all cases. We document a statistically significant epidemiological paternal age effect of 6.3 years excess for fathers of MYHRS probands. We developed an ultra-sensitive assay to quantify spontaneous MYHRS-causing SMAD4 variants in sperm and show that pathogenic variants at codon 500 are found at elevated level in sperm of most men and exhibit a strong positive correlation with donor's age, indicative of a high apparent germline mutation rate. Finally, we performed in vitro assays to validate the peculiar functional behavior of the clonally selected DNMs and explored the basis of the pathophysiology of the different SMAD4 sperm-enriched variants. Taken together, these data provide compelling evidence that SMAD4, a gene operating outside the canonical RAS-MAPK signaling pathway, is associated with selfish spermatogonial selection and raises the possibility that other genes/pathways are under positive selection in the aging human testis.
RESUMEN
The endosomal sorting complex required for transport (ESCRT) machinery is essential for membrane remodeling and autophagy and it comprises three multi-subunit complexes (ESCRT I-III). We report nine individuals from six families presenting with a spectrum of neurodevelopmental/neurodegenerative features caused by bi-allelic variants in SNF8 (GenBank: NM_007241.4), encoding the ESCRT-II subunit SNF8. The phenotypic spectrum included four individuals with severe developmental and epileptic encephalopathy, massive reduction of white matter, hypo-/aplasia of the corpus callosum, neurodevelopmental arrest, and early death. A second cohort shows a milder phenotype with intellectual disability, childhood-onset optic atrophy, or ataxia. All mildly affected individuals shared the same hypomorphic variant, c.304G>A (p.Val102Ile). In patient-derived fibroblasts, bi-allelic SNF8 variants cause loss of ESCRT-II subunits. Snf8 loss of function in zebrafish results in global developmental delay and altered embryo morphology, impaired optic nerve development, and reduced forebrain size. In vivo experiments corroborated the pathogenicity of the tested SNF8 variants and their variable impact on embryo development, validating the observed clinical heterogeneity. Taken together, we conclude that loss of ESCRT-II due to bi-allelic SNF8 variants is associated with a spectrum of neurodevelopmental/neurodegenerative phenotypes mediated likely via impairment of the autophagic flux.
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Epilepsia Generalizada , Atrofia Óptica , Animales , Humanos , Niño , Pez Cebra/genética , Atrofia Óptica/genética , Fenotipo , Complejos de Clasificación Endosomal Requeridos para el Transporte/genéticaRESUMEN
We previously molecularly and clinically characterized Mazzanti syndrome, a RASopathy related to Noonan syndrome that is mostly caused by a single recurrent missense variant (c.4A > G, p.Ser2Gly) in SHOC2, which encodes a leucine-rich repeat-containing protein facilitating signal flow through the RAS-mitogen-associated protein kinase (MAPK) pathway. We also documented that the pathogenic p.Ser2Gly substitution causes upregulation of MAPK signaling and constitutive targeting of SHOC2 to the plasma membrane due to the introduction of an N-myristoylation recognition motif. The almost invariant occurrence of the pathogenic c.4A > G missense change in SHOC2 is mirrored by a relatively homogeneous clinical phenotype of Mazzanti syndrome. Here, we provide new data on the clinical spectrum and molecular diversity of this disorder and functionally characterize new pathogenic variants. The clinical phenotype of six unrelated individuals carrying novel disease-causing SHOC2 variants is delineated, and public and newly collected clinical data are utilized to profile the disorder. In silico, in vitro and in vivo characterization of the newly identified variants provides evidence that the consequences of these missense changes on SHOC2 functional behavior differ from what had been observed for the canonical p.Ser2Gly change but converge toward an enhanced activation of the RAS-MAPK pathway. Our findings expand the molecular spectrum of pathogenic SHOC2 variants, provide a more accurate picture of the phenotypic expression associated with variants in this gene and definitively establish a gain-of-function behavior as the mechanism of disease.
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Anomalías Múltiples , Péptidos y Proteínas de Señalización Intracelular , Síndrome del Cabello Anágeno Suelto , Anomalías Múltiples/genética , Humanos , Péptidos y Proteínas de Señalización Intracelular/genética , Síndrome del Cabello Anágeno Suelto/genética , Fenotipo , Proteínas ras/genética , Proteínas ras/metabolismoRESUMEN
Bardet-Biedl syndrome (BBS) is a rare recessive multisystem disorder characterized by retinitis pigmentosa, obesity, postaxial polydactyly, cognitive deficits, and genitourinary defects. BBS is clinically variable and genetically heterogeneous, with 26 genes identified to contribute to the disorder when mutated, the majority encoding proteins playing role in primary cilium biogenesis, intraflagellar transport, and ciliary trafficking. Here, we report on an 18-year-old boy with features including severe photophobia and central vision loss since childhood, hexadactyly of the right foot and a supernumerary nipple, which were suggestive of BBS. Genetic analyses using targeted resequencing and exome sequencing failed to provide a conclusive genetic diagnosis. Whole-genome sequencing (WGS) allowed us to identify compound heterozygosity for a missense variant and a large intragenic deletion encompassing exon 12 in BBS9 as underlying the condition. We assessed the functional impact of the identified variants and demonstrated that they impair BBS9 function, with significant consequences for primary cilium formation and morphology. Overall, this study further highlights the usefulness of WGS in the diagnostic workflow of rare diseases to reach a definitive diagnosis. This report also remarks on a requirement for functional validation analyses to more effectively classify variants that are identified in the frame of the diagnostic workflow.
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Síndrome de Bardet-Biedl , Secuenciación Completa del Genoma , Síndrome de Bardet-Biedl/genética , Síndrome de Bardet-Biedl/diagnóstico , Humanos , Masculino , Adolescente , Cilios/patología , Cilios/genética , Proteínas del CitoesqueletoRESUMEN
Gain of function pathogenic variants in MRAS have been found in a small subset of pediatric subjects presenting with Noonan syndrome (NS) associated with hypertrophic cardiomyopathy (HCM) and moderate to severe intellectual disability. These variants are considered to confer a high-risk for the development of severe HCM with poor prognosis and fatal outcome. We report on the natural history of the first adult subject with NS carrying the recurrent pathogenic p.Thr68Ile amino acid substitution. Different from what had previously been observed, he presented with a mild, late-onset left ventricular hypertrophy, and a constellation of additional symptoms rarely seen in NS. The present case provides evidence that HCM does not represent an obligatory, early-onset and severe complication in subjects with MRAS variants. It also adds new data about late-onset features suggesting that other unexpected complications might be observed in adult subjects providing anticipatory guidance for individuals of all age.
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Cardiomiopatía Hipertrófica , Síndrome de Noonan , Masculino , Niño , Humanos , Adulto , Síndrome de Noonan/complicaciones , Síndrome de Noonan/genética , Síndrome de Noonan/diagnóstico , Hipertrofia Ventricular Izquierda/genética , Hipertrofia Ventricular Izquierda/complicaciones , Cardiomiopatía Hipertrófica/genética , Sustitución de Aminoácidos , Mutación , Fenotipo , Proteínas ras/genéticaRESUMEN
Inherited retinal degeneration (IRD) represents a clinically variable and genetically heterogeneous group of disorders characterized by photoreceptor dysfunction. These diseases typically present with progressive severe vision loss and variable onset, ranging from birth to adulthood. Genomic sequencing has allowed to identify novel IRD-related genes, most of which encode proteins contributing to photoreceptor-cilia biogenesis and/or function. Despite these insights, knowledge gaps hamper a molecular diagnosis in one-third of IRD cases. By exome sequencing in a cohort of molecularly unsolved individuals with IRD, we identified a homozygous splice site variant affecting the transcript processing of TUB, encoding the first member of the Tubby family of bipartite transcription factors, in a sporadic case with retinal dystrophy. A truncating homozygous variant in this gene had previously been reported in a single family with three subjects sharing retinal dystrophy and obesity. The clinical assessment of the present patient documented a slightly increased body mass index and no changes in metabolic markers of obesity, but confirmed the occurrence of retinal detachment. In vitro studies using patient-derived fibroblasts showed the accelerated degradation of the encoded protein and aberrant cilium morphology and biogenesis. These findings definitely link impaired TUB function to retinal dystrophy and provide new data on the clinical characterization of this ultra-rare retinal ciliopathy.
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Ciliopatías , Distrofias Retinianas , Humanos , Adulto , Cilios/genética , Retina , Ciliopatías/genética , Distrofias Retinianas/genética , Proteínas/genética , Obesidad , Mutación , LinajeRESUMEN
UBE2A deficiency, that is, intellectual disability (ID) Nascimento type (MIM 300860), is an X-linked syndrome characterized by developmental delay, moderate to severe ID, seizures, dysmorphisms, skin anomalies, and urogenital malformations. Forty affected subjects have been reported thus far, with 31 cases having intragenic UBE2A variants. Here, we report on additional eight affected subjects from seven unrelated families who were found to be hemizygous for previously unreported UBE2A missense variants (p.Glu62Lys, p.Arg95Cys, p.Thr99Ala, and p.Arg135Trp) or small in-frame deletions (p.Val81_Ala83del, and p.Asp101del). A wide phenotypic spectrum was documented in these subjects, ranging from moderate ID associated with mild dysmorphisms to severe features including congenital heart defects (CHD), severe cognitive impairment, and pineal gland tumors. Four variants affected residues (Glu62, Arg95, Thr99 and Asp101) that contribute to stabilizing the structure of the E3 binding domain. The three-residue in-frame deletion, p.Val81_Ala83del, resulted from aberrant processing of the transcript. This variant and p.Arg135Trp mapped to regions of the protein located far from the E3 binding region, and caused variably accelerated protein degradation. By reviewing available clinical information, we revise the clinical and molecular profile of the disorder and document genotype-phenotype correlations. Pineal gland cysts/tumors, CHD and hypogammaglobulinemia emerge as recurrent features.
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Enfermedades Genéticas Ligadas al Cromosoma X/genética , Cardiopatías Congénitas/genética , Discapacidad Intelectual/genética , Enzimas Ubiquitina-Conjugadoras/genética , Preescolar , Femenino , Enfermedades Genéticas Ligadas al Cromosoma X/complicaciones , Enfermedades Genéticas Ligadas al Cromosoma X/patología , Predisposición Genética a la Enfermedad , Cardiopatías Congénitas/complicaciones , Cardiopatías Congénitas/patología , Humanos , Lactante , Discapacidad Intelectual/complicaciones , Discapacidad Intelectual/patología , Masculino , Linaje , Anomalías Cutáneas/complicaciones , Anomalías Cutáneas/genética , Anomalías Cutáneas/patología , Anomalías Urogenitales/complicaciones , Anomalías Urogenitales/genética , Anomalías Urogenitales/patologíaRESUMEN
Primrose syndrome (PS; MIM# 259050) is characterized by intellectual disability (ID), macrocephaly, unusual facial features (frontal bossing, deeply set eyes, down-slanting palpebral fissures), calcified external ears, sparse body hair and distal muscle wasting. The syndrome is caused by de novo heterozygous missense variants in ZBTB20. Most of the 29 published patients are adults as characteristics appear more recognizable with age. We present 13 hitherto unpublished individuals and summarize the clinical and molecular findings in all 42 patients. Several signs and symptoms of PS develop during childhood, but the cardinal features, such as calcification of the external ears, cystic bone lesions, muscle wasting, and contractures typically develop between 10 and 16 years of age. Biochemically, anemia and increased alpha-fetoprotein levels are often present. Two adult males with PS developed a testicular tumor. Although PS should be regarded as a progressive entity, there are no indications that cognition becomes more impaired with age. No obvious genotype-phenotype correlation is present. A subgroup of patients with ZBTB20 variants may be associated with mild, nonspecific ID. Metabolic investigations suggest a disturbed mitochondrial fatty acid oxidation. We suggest a regular surveillance in all adult males with PS until it is clear whether or not there is a truly elevated risk of testicular cancer.
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Anomalías Múltiples/genética , Calcinosis/genética , Enfermedades del Oído/genética , Predisposición Genética a la Enfermedad , Discapacidad Intelectual/genética , Megalencefalia/genética , Atrofia Muscular/genética , Proteínas del Tejido Nervioso/genética , Factores de Transcripción/genética , 3-Hidroxiacil-CoA Deshidrogenasas/genética , Anomalías Múltiples/patología , Acetil-CoA C-Aciltransferasa/genética , Adolescente , Adulto , Calcinosis/patología , Isomerasas de Doble Vínculo Carbono-Carbono/genética , Niño , Preescolar , Enfermedades del Oído/patología , Enoil-CoA Hidratasa/genética , Cara/anomalías , Femenino , Estudios de Asociación Genética , Heterocigoto , Humanos , Lactante , Discapacidad Intelectual/patología , Masculino , Megalencefalia/patología , Persona de Mediana Edad , Mitocondrias/genética , Mitocondrias/patología , Atrofia Muscular/patología , Mutación , Mutación Missense/genética , Fenotipo , Racemasas y Epimerasas/genética , Neoplasias Testiculares , Adulto JovenRESUMEN
Inherited retinal dystrophies (IRDs) are a group of clinically and genetically heterogeneous degenerative disorders. To date, mutations have been associated with IRDs in over 270 disease genes, but molecular diagnosis still remains elusive in about a third of cases. The methodologic developments in genome sequencing techniques that we have witnessed in this last decade have represented a turning point not only in diagnosis and prognosis but, above all, in the identification of new therapeutic perspectives. The discovery of new disease genes and pathogenetic mechanisms underlying IRDs has laid the groundwork for gene therapy approaches. Several clinical trials are ongoing, and the recent approval of Luxturna, the first gene therapy product for Leber congenital amaurosis, marks the beginning of a new era. Due to its anatomical and functional characteristics, the retina is the organ of choice for gene therapy, although there are quite a few difficulties in the translational approaches from preclinical models to humans. In the first part of this review, an overview of the current knowledge on methodological issues and future perspectives of gene therapy applied to IRDs is discussed; in the second part, the state of the art of clinical trials on the gene therapy approach in IRDs is illustrated.
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Terapia Genética , Distrofias Retinianas/genética , Distrofias Retinianas/terapia , Animales , Modelos Animales de Enfermedad , Edición Génica , Técnicas de Transferencia de Gen , Predisposición Genética a la Enfermedad , Terapia Genética/métodos , Vectores Genéticos/genética , Humanos , Distrofias Retinianas/diagnóstico , Transgenes , Resultado del TratamientoRESUMEN
SHOC2 is a scaffold protein composed almost entirely by leucine-rich repeats (LRRs) and having an N-terminal region enriched in alternating lysine and glutamate/aspartate residues (KEKE motifs). SHOC2 acts as a positive modulator of the RAS-RAF-MEK-ERK signalling cascade by favouring stable RAF1 interaction with RAS. We previously reported that the p.Ser2Gly substitution in SHOC2 underlies Mazzanti syndrome, a RASopathy clinically overlapping Noonan syndrome, promoting N-myristoylation and constitutive targeting of the mutant to the plasma membrane. We also documented transient nuclear translocation of wild-type SHOC2 upon EGF stimulation, suggesting a more complex function in signal transduction.Here, we characterized the domains controlling SHOC2 shuttling between the nucleus and cytoplasm, and those contributing to SHOC2S2G mistargeting to the plasma membrane, analysed the structural organization of SHOC2's LRR motifs, and determined the impact of SHOC2 mislocalization on ERK signalling. We show that LRRs 1 to 13 constitute a structurally recognizable domain required for SHOC2 import into the nucleus and constitutive targeting of SHOC2S2G to the plasma membrane, while the KEKE motif-rich region is necessary to achieve efficient SHOC2 export from the nucleus. We also document that SHOC2S2G localizes both in raft and non-raft domains, and that it translocates to the non-raft domains following stimulation. Finally, we demonstrate that SHOC2 trapping at different subcellular sites has a diverse impact on ERK signalling strength and dynamics, suggesting a dual counteracting modulatory role of SHOC2 in the control of ERK signalling exerted at different intracellular compartments.
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Núcleo Celular/metabolismo , Citoplasma/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Síndrome del Cabello Anágeno Suelto/genética , Síndrome de Noonan/genética , Secuencias de Aminoácidos , Animales , Células COS , Línea Celular , Chlorocebus aethiops , Células HEK293 , Humanos , Péptidos y Proteínas de Señalización Intracelular/química , Péptidos y Proteínas de Señalización Intracelular/genética , Sistema de Señalización de MAP Quinasas , Ratones , Células 3T3 NIH , Transporte de ProteínasRESUMEN
The RASopathies constitute a family of autosomal-dominant disorders whose major features include facial dysmorphism, cardiac defects, reduced postnatal growth, variable cognitive deficits, ectodermal and skeletal anomalies, and susceptibility to certain malignancies. Noonan syndrome (NS), the commonest RASopathy, is genetically heterogeneous and caused by functional dysregulation of signal transducers and regulatory proteins with roles in the RAS/extracellular signal-regulated kinase (ERK) signal transduction pathway. Mutations in known disease genes account for approximately 80% of affected individuals. Here, we report that missense mutations altering Son of Sevenless, Drosophila, homolog 2 (SOS2), which encodes a RAS guanine nucleotide exchange factor, occur in a small percentage of subjects with NS. Four missense mutations were identified in five unrelated sporadic cases and families transmitting NS. Disease-causing mutations affected three conserved residues located in the Dbl homology (DH) domain, of which two are directly involved in the intramolecular binding network maintaining SOS2 in its autoinhibited conformation. All mutations were found to promote enhanced signaling from RAS to ERK. Similar to NS-causing SOS1 mutations, the phenotype associated with SOS2 defects is characterized by normal development and growth, as well as marked ectodermal involvement. Unlike SOS1 mutations, however, those in SOS2 are restricted to the DH domain.
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Estudios de Asociación Genética , Mutación , Síndrome de Noonan/genética , Dominios y Motivos de Interacción de Proteínas/genética , Proteínas Son Of Sevenless/genética , Adolescente , Adulto , Alelos , Sustitución de Aminoácidos , Niño , Análisis Mutacional de ADN , Exoma , Facies , Femenino , Genotipo , Humanos , Masculino , Modelos Moleculares , Síndrome de Noonan/diagnóstico , Fenotipo , Conformación Proteica , Proteínas Son Of Sevenless/química , Adulto JovenRESUMEN
Noonan-like syndrome with loose anagen hair (NSLH), also known as Mazzanti syndrome, is a RASopathy characterized by craniofacial features resembling Noonan syndrome, cardiac defects, cognitive deficits and behavioral issues, reduced growth generally associated with GH deficit, darkly pigmented skin, and an unique combination of ectodermal anomalies. Virtually all cases of NSLH are caused by an invariant and functionally unique mutation in SHOC2 (c.4A>G, p.Ser2Gly). Here, we report on a child with molecularly confirmed NSLH who developed a neuroblastoma, first suspected at the age 3 months by abdominal ultrasound examination. Based on this finding, scanning of the SHOC2 coding sequence encompassing the c.4A>G change was performed on selected pediatric cohorts of malignancies documented to occur in RASopathies (i.e., neuroblastoma, brain tumors, rhabdomyosarcoma, acute lymphoblastic, and myeloid leukemia), but failed to identify a functionally relevant cancer-associated variant. While these results do not support a major role of somatic SHOC2 mutations in these pediatric cancers, this second instance of neuroblastoma in NSLAH suggests a possible predisposition to this malignancy in subjects heterozygous for the c.4A>G SHOC2 mutation.
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Neuroblastoma/complicaciones , Síndrome de Noonan/fisiopatología , Humanos , Recién Nacido , Masculino , Síndrome de Noonan/complicacionesRESUMEN
Fetal hydrops is a condition resulting from interstitial fluid accumulation in fetal compartments secondary to increased capillary permeability and characterized by high rates of perinatal mortality and morbidity. Clinical features include skin edema, hydrothorax, pericardial effusion, ascites with or without polyhydramnios, and placental edema. While it may occur as associated feature in multiple disorders, it has been documented to recur in Noonan syndrome, the most common disorder among RASopathies, but also in cardiofaciocutaneous and Costello syndromes. Here, we report on the occurrence of severe hydrops in a newborn heterozygous for the invariant c.4A>G missense change in SHOC2 which underlies Noonan-like syndrome with loose anagen hair, documenting that it represents a clinically relevant complication in this condition, shared by RASopathies.
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Hidropesía Fetal/genética , Péptidos y Proteínas de Señalización Intracelular/genética , Mutación , Heterocigoto , Humanos , Recién Nacido , Síndrome del Cabello Anágeno Suelto/genética , Síndrome de Noonan/genéticaRESUMEN
Pathogenic, largely truncating variants in the ETS2 repressor factor (ERF) gene, encoding a transcriptional regulator negatively controlling RAS-MAPK signaling, have been associated with syndromic craniosynostosis involving various cranial sutures and Chitayat syndrome, an ultrarare condition with respiratory distress, skeletal anomalies, and facial dysmorphism. Recently, a single patient with craniosynostosis and a phenotype resembling Noonan syndrome (NS), the most common disorder among the RASopathies, was reported to carry a de novo loss-of-function variant in ERF. Here, we clinically profile 26 individuals from 15 unrelated families carrying different germline heterozygous variants in ERF and showing a phenotype reminiscent of NS. The majority of subjects presented with a variable degree of global developmental and/or language delay. Their shared facial features included absolute/relative macrocephaly, high forehead, hypertelorism, palpebral ptosis, wide nasal bridge, and low-set/posteriorly angulated ears. Stature was below the 3rd centile in two-third of the individuals, while no subject showed typical NS cardiac involvement. Notably, craniosynostosis was documented only in three unrelated individuals, while a dolichocephalic aspect of the skull in absence of any other evidence supporting a premature closing of sutures was observed in other 10 subjects. Unilateral Wilms tumor was diagnosed in one individual. Most cases were familial, indicating an overall low impact on fitness. Variants were nonsense and frameshift changes, supporting ERF haploinsufficiency. These findings provide evidence that heterozygous loss-of-function variants in ERF cause a "RASopathy" resembling NS with or without craniosynostosis, and allow a first dissection of the molecular circuits contributing to MAPK signaling pleiotropy.
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Craneosinostosis , Síndrome de Noonan , Fenotipo , Humanos , Craneosinostosis/genética , Craneosinostosis/patología , Femenino , Masculino , Síndrome de Noonan/genética , Síndrome de Noonan/patología , Niño , Preescolar , Lactante , Mutación con Pérdida de Función , Adolescente , Proteínas Represoras/genética , AdultoRESUMEN
RAC1 is a member of the Rac/Rho GTPase subfamily within the RAS superfamily of small GTP-binding proteins, comprising 3 paralogs playing a critical role in actin cytoskeleton remodeling, cell migration, proliferation and differentiation. De novo missense variants in RAC1 are associated with a rare neurodevelopmental disorder (MRD48) characterized by DD/ID and brain abnormalities coupled with a wide range of additional features. Structural and functional studies have documented either a dominant negative or constitutively active behavior for a subset of mutations. Here, we describe two individuals with previously unreported de novo missense RAC1 variants. We functionally demonstrate their pathogenicity proving a gain-of-function (GoF) effect for both. By reviewing the clinical features of these two individuals and the previously published MRD48 subjects, we further delineate the clinical profile of the disorder, confirming its phenotypic variability. Moreover, we compare the main features of MRD48 with the neurodevelopmental disease caused by GoF variants in the paralog RAC3, highlighting similarities and differences. Finally, we review all previously reported variants in RAC proteins and in the closely related CDC42, providing an updated overview of the spectrum and hotspots of pathogenic variants affecting these functionally related GTPases.
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Trastornos del Neurodesarrollo , Proteína de Unión al GTP rac1 , Humanos , Proteína de Unión al GTP rac1/genética , Proteína de Unión al GTP rac1/química , Proteína de Unión al GTP rac1/metabolismo , Proteínas de Unión al GTP rac/genética , Mutación , Trastornos del Neurodesarrollo/genética , Mutación MissenseRESUMEN
OBJECTIVE: The co-occurrence of pathogenic variants has emerged as a relatively common finding underlying complex phenotypes. Here, we used whole-exome sequencing (WES) to solve an unclassified multisystem clinical presentation. PATIENTS AND METHODS: A 20-year-old woman affected by moderate intellectual disability (ID), dysmorphic features, hypertrichosis, scoliosis, recurrent bronchitis, and pneumonia with bronchiectasis, colelithiasis, chronic severe constipation, and a family history suggestive of autosomal dominant recurrence of polycystic kidney disease was analyzed by WES to identify the genomic events underlying the condition. RESULTS: Four co-occurring genomic events fully explaining the proband's clinical features were identified. A de novo truncating USP7 variant was disclosed as the cause of Hao-Fountain syndrome, a disorder characterized by syndromic ID and distinctive behavior. Compound heterozygosity for a major cystic fibrosis-causing variant and the modulator allele, IVS8-5T, in CFTR explained the recurrent upper and lower respiratory way infections, bronchiectasis, cholelithiasis, and chronic constipation. Finally, a truncating PKD2 variant co-segregating with polycystic kidney disease in the family allowed presymptomatic disease diagnosis. CONCLUSIONS: The co-occurring variants in USP7 and CFTR variants explained the multisystem disorder of the patient. The comprehensive dissection of the phenotype and early diagnosis of autosomal dominant polycystic kidney disease allowed us to manage the CFTR-related disorder symptoms and monitor renal function and other complications associated with PKD2 haploinsufficiency, addressing proper care and surveillance.
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Bronquiectasia , Riñón Poliquístico Autosómico Dominante , Anomalías Múltiples , Enfermedades del Desarrollo Óseo , Bronquiectasia/genética , Estreñimiento/genética , Anomalías Craneofaciales , Regulador de Conductancia de Transmembrana de Fibrosis Quística/genética , Sordera , Exoma/genética , Genómica , Humanos , Discapacidad Intelectual , Riñón Poliquístico Autosómico Dominante/genética , Peptidasa Específica de Ubiquitina 7/genética , Secuenciación del ExomaRESUMEN
Noonan syndrome (NS) is among the most common nonchromosomal disorders affecting development and growth. NS is caused by aberrant RAS-MAPK signaling and is genetically heterogeneous, which explains, in part, the marked clinical variability documented for this Mendelian trait. Recently, we and others identified SOS1 as a major gene underlying NS. Here, we explored further the spectrum of SOS1 mutations and their associated phenotypic features. Mutation scanning of the entire SOS1 coding sequence allowed the identification of 33 different variants deemed to be of pathological significance, including 16 novel missense changes and in-frame indels. Various mutation clusters destabilizing or altering orientation of regions of the protein predicted to contribute structurally to the maintenance of autoinhibition were identified. Two previously unappreciated clusters predicted to enhance SOS1's recruitment to the plasma membrane, thus promoting a spatial reorientation of domains contributing to inhibition, were also recognized. Genotype-phenotype analysis confirmed our previous observations, establishing a high frequency of ectodermal anomalies and a low prevalence of cognitive impairment and reduced growth. Finally, mutation analysis performed on cohorts of individuals with nonsyndromic pulmonic stenosis, atrial septal defects, and ventricular septal defects excluded a major contribution of germline SOS1 lesions to the isolated occurrence of these cardiac anomalies.
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Síndrome de Noonan/diagnóstico , Síndrome de Noonan/genética , Proteína SOS1/genética , Adolescente , Adulto , Niño , Exones , Femenino , Estudios de Asociación Genética , Defectos del Tabique Interatrial/genética , Defectos del Tabique Interventricular/genética , Humanos , Mutación INDEL/genética , Intrones , Masculino , Quinasas de Proteína Quinasa Activadas por Mitógenos/genética , Mutación , Mutación Missense/genética , Conformación Proteica , Estenosis de la Válvula Pulmonar/genética , Proteína SOS1/químicaRESUMEN
Objective, the application of genomic sequencing in clinical practice has allowed us to appreciate the contribution of co-occurring pathogenic variants to complex and unclassified clinical phenotypes. Besides the clinical relevance, these findings have provided evidence of previously unrecognized functional links between genes in the context of developmental processes and physiology. Patients and Methods, a 5-year-old patient showing an unclassified phenotype characterized by developmental delay, speech delay, peculiar behavioral features, facial dysmorphism and severe cardiopathy was analyzed by trio-based whole exome sequencing (WES) analysis to identify the genomic events underlying the condition. Results, two co-occurring heterozygous truncating variants in CNOT3 and SMAD6 were identified. Heterozygous loss-of-function variants in CNOT3, encoding a subunit of the CCR4-NOT protein complex, have recently been reported to cause a syndromic condition known as intellectual developmental disorder with speech delay, autism and dysmorphic facies (IDDSADF). Enrichment of rare/private variants in the SMAD6 gene, encoding a protein negatively controlling transforming growth factor ß/bone morphogenetic protein (TGFB/BMP) signaling, has been described in association with a wide spectrum of congenital heart defects. We dissected the contribution of individual variants to the complex clinical manifestations and profiled a previously unappreciated set of facial features and signs characterizing IDDSADF. Conclusions, two concomitant truncating variants in CNOT3 and SMAD6 are the cause of the combination of features documented in the patient resulting in the unique multisystem neurodevelopmental condition. These findings provide evidence for a functional link between the CCR4-NOT complex and TGFB/BMP signaling in processes controlling cardiac development. Finally, the present revision provides evidence that IDDSADF is characterized by a distinctive facial gestalt.
Asunto(s)
Trastorno Autístico/patología , Predisposición Genética a la Enfermedad , Discapacidad Intelectual/patología , Trastornos del Desarrollo del Lenguaje/patología , Proteína smad6/genética , Factores de Transcripción/genética , Trastorno Autístico/genética , Preescolar , Heterocigoto , Humanos , Discapacidad Intelectual/genética , Trastornos del Desarrollo del Lenguaje/genética , Masculino , Secuenciación del ExomaRESUMEN
OBJECTIVE: To investigate the molecular cause(s) underlying a severe form of infantile-onset parkinsonism and characterize functionally the identified variants. METHODS: A trio-based whole exome sequencing (WES) approach was used to identify the candidate variants underlying the disorder. In silico modeling, and in vitro and in vivo studies were performed to explore the impact of these variants on protein function and relevant cellular processes. RESULTS: WES analysis identified biallelic variants in WARS2, encoding the mitochondrial tryptophanyl tRNA synthetase (mtTrpRS), a gene whose mutations have recently been associated with multiple neurological phenotypes, including childhood-onset, levodopa-responsive or unresponsive parkinsonism in a few patients. A substantial reduction of mtTrpRS levels in mitochondria and reduced OXPHOS function was demonstrated, supporting their pathogenicity. Based on the infantile-onset and severity of the phenotype, additional variants were considered as possible genetic modifiers. Functional assessment of a selected panel of candidates pointed to a de novo missense mutation in CHRNA6, encoding the α6 subunit of neuronal nicotinic receptors, which are involved in the cholinergic modulation of dopamine release in the striatum, as a second event likely contributing to the phenotype. In silico, in vitro (Xenopus oocytes and GH4C1 cells) and in vivo (C. elegans) analyses demonstrated the disruptive effects of the mutation on acetylcholine receptor structure and function. CONCLUSION: Our findings consolidate the association between biallelic WARS2 mutations and movement disorders, and suggest CHRNA6 as a genetic modifier of the phenotype.
Asunto(s)
Trastornos Parkinsonianos/genética , Receptores Nicotínicos/genética , Triptófano-ARNt Ligasa/genética , Edad de Inicio , Niño , Humanos , Masculino , Mutación , Índice de Severidad de la Enfermedad , Secuenciación del ExomaRESUMEN
Noonan, LEOPARD, and cardiofaciocutaneous syndromes (NS, LS, and CFCS) are developmental disorders with overlapping features including distinctive facial dysmorphia, reduced growth, cardiac defects, skeletal and ectodermal anomalies, and variable cognitive deficits. Dysregulated RAS-mitogen-activated protein kinase (MAPK) signal traffic has been established to represent the molecular pathogenic cause underlying these conditions. To investigate the phenotypic spectrum and molecular diversity of germline mutations affecting BRAF, which encodes a serine/threonine kinase functioning as a RAS effector frequently mutated in CFCS, subjects with a diagnosis of NS (N=270), LS (N=6), and CFCS (N=33), and no mutation in PTPN11, SOS1, KRAS, RAF1, MEK1, or MEK2, were screened for the entire coding sequence of the gene. Besides the expected high prevalence of mutations observed among CFCS patients (52%), a de novo heterozygous missense change was identified in one subject with LS (17%) and five individuals with NS (1.9%). Mutations mapped to multiple protein domains and largely did not overlap with cancer-associated defects. NS-causing mutations had not been documented in CFCS, suggesting that the phenotypes arising from germline BRAF defects might be allele specific. Selected mutant BRAF proteins promoted variable gain of function of the kinase, but appeared less activating compared to the recurrent cancer-associated p.Val600Glu mutant. Our findings provide evidence for a wide phenotypic diversity associated with mutations affecting BRAF, and occurrence of a clinical continuum associated with these molecular lesions.