RESUMEN
PURPOSE: Coffin-Siris and Nicolaides-Baraitser syndromes are recognizable neurodevelopmental disorders caused by germline variants in BAF complex subunits. The SMARCC2 BAFopathy was recently reported. Herein, we present clinical and molecular data on a large cohort. METHODS: Clinical symptoms for 41 novel and 24 previously published affected individuals were analyzed using the Human Phenotype Ontology. For genotype-phenotype correlations, molecular data were standardized and grouped into non-truncating and likely gene-disrupting (LGD) variants. Missense variant protein expression and BAF-subunit interactions were examined using 3D protein modeling, co-immunoprecipitation, and proximity-ligation assays. RESULTS: Neurodevelopmental delay with intellectual disability, muscular hypotonia, and behavioral disorders were the major manifestations. Clinical hallmarks of BAFopathies were rare. Clinical presentation differed significantly, with LGD variants being predominantly inherited and associated with mildly reduced or normal cognitive development, whereas non-truncating variants were mostly de novo and presented with severe developmental delay. These distinct manifestations and non-truncating variant clustering in functional domains suggest different pathomechanisms. In vitro testing showed decreased protein expression for N-terminal missense variants similar to LGD. CONCLUSION: This study improved SMARCC2 variant classification and identified discernible SMARCC2-associated phenotypes for LGD and non-truncating variants, which were distinct from other BAFopathies. The pathomechanism of most non-truncating variants has yet to be investigated.
Asunto(s)
Anomalías Múltiples , Discapacidad Intelectual , Micrognatismo , Trastornos del Neurodesarrollo , Humanos , Anomalías Múltiples/genética , Cara , Micrognatismo/genética , Discapacidad Intelectual/genética , Discapacidad Intelectual/complicaciones , Facies , Fenotipo , Proteínas de Unión al ADN/genética , Factores de Transcripción/genéticaRESUMEN
Multilocus imprinting disturbances (MLID) have been associated with up to 12% of patients with Beckwith-Wiedemann syndrome, Silver-Russell syndrome, and pseudohypoparathyroidism type 1B (PHP1B). Single-gene defects affecting components of the subcortical maternal complex (SCMC) have been reported in cases with multilocus hypomethylation defects. We present a patient with speech and language impairment with mild Angelman syndrome (AS) features who demonstrates maternal hypomethylation at 15q11.2 (SNRPN) as well as 11p15.5 (KCNQ1OT1) imprinted loci, but normal methylation at 6q24.2 (PLAGL1), 7p12.1 (GRB10), 7q32.2 (MEST), 11p15.5 (H19), 14q32.2 (MEG3), 19q13.43 (PEG3), and 20q13.32 (GNAS and GNAS-AS1). The proband also has no copy number nor sequence variants within the AS imprinting center or in UBE3A. Maternal targeted next generation sequencing did not identify any pathogenic variants in ZPF57, NLRP2, NLRP5, NLRP7, KHDC3L, PADI6, TLE6, OOEP, UHRF1 or ZAR1. The presence of very delayed, yet functional speech, behavioral difficulties, EEG abnormalities but without clinical seizures, and normocephaly are consistent with the 15q11.2 hypomethylation defect observed in this patient. To our knowledge, this is the first report of MLID in a patient with mild, likely mosaic, Angelman syndrome.
Asunto(s)
Síndrome de Angelman , Síndrome de Beckwith-Wiedemann , Discapacidad Intelectual , Trastornos del Desarrollo del Lenguaje , Proteínas Adaptadoras Transductoras de Señales/genética , Síndrome de Angelman/diagnóstico , Síndrome de Angelman/genética , Síndrome de Beckwith-Wiedemann/complicaciones , Síndrome de Beckwith-Wiedemann/diagnóstico , Síndrome de Beckwith-Wiedemann/genética , Proteínas Potenciadoras de Unión a CCAAT , Niño , Metilación de ADN , Impresión Genómica , Humanos , Discapacidad Intelectual/diagnóstico , Discapacidad Intelectual/genética , Trastornos del Desarrollo del Lenguaje/genética , Ubiquitina-Proteína LigasasRESUMEN
BACKGROUND: Semaphorins and plexins are ligands and cell surface receptors that regulate multiple neurodevelopmental processes such as axonal growth and guidance. PLXNA3 is a plexin gene located on the X chromosome that encodes the most widely expressed plexin receptor in fetal brain, plexin-A3. Plexin-A3 knockout mice demonstrate its role in semaphorin signaling in vivo. The clinical manifestations of semaphorin/plexin neurodevelopmental disorders have been less widely explored. This study describes the neurological and neurodevelopmental phenotypes of boys with maternally inherited hemizygous PLXNA3 variants. METHODS: Data-sharing through GeneDx and GeneMatcher allowed identification of individuals with autism or intellectual disabilities (autism/ID) and hemizygous PLXNA3 variants in collaboration with their physicians and genetic counselors, who completed questionnaires about their patients. In silico analyses predicted pathogenicity for each PLXNA3 variant. RESULTS: We assessed 14 boys (mean age, 10.7 [range 2 to 25] years) with maternally inherited hemizygous PLXNA3 variants and autism/ID ranging from mild to severe. Other findings included fine motor dyspraxia (92%), attention-deficit/hyperactivity traits, and aggressive behaviors (63%). Six patients (43%) had seizures. Thirteen boys (93%) with PLXNA3 variants showed novel or very low allele frequencies and probable damaging/disease-causing pathogenicity in one or more predictors. We found a genotype-phenotype correlation between PLXNA3 cytoplasmic domain variants (exons 22 to 32) and more severe neurodevelopmental disorder phenotypes (P < 0.05). CONCLUSIONS: We report 14 boys with maternally inherited, hemizygous PLXNA3 variants and a range of neurodevelopmental disorders suggesting a novel X-linked intellectual disability syndrome. Greater understanding of PLXNA3 variant pathogenicity in humans will require additional clinical, computational, and experimental validation.
Asunto(s)
Trastorno del Espectro Autista/genética , Moléculas de Adhesión Celular/fisiología , Discapacidad Intelectual/genética , Proteínas del Tejido Nervioso/fisiología , Receptores de Superficie Celular/genética , Semaforinas/fisiología , Adolescente , Adulto , Trastorno del Espectro Autista/fisiopatología , Niño , Preescolar , Estudios de Asociación Genética , Humanos , Discapacidad Intelectual/fisiopatología , Masculino , Transducción de Señal/fisiología , Adulto JovenRESUMEN
BACKGROUND: TANGO2-related metabolic encephalopathy and arrhythmias (TRMEA) is a rare, phenotypically heterogeneous, neurological disease affecting children. METHODS: We conducted a chart review of five children with molecularly confirmed TRMEA diagnosed at our institution and compiled pathogenic variant frequency and symptom prevalence from cases previously reported in the literature. RESULTS: Including those patients in our case series, 76 patients with TRMEA have been described. Developmental delay (93%) and/or regression (71%), spasticity (78%), and seizures (57%) are common in TRMEA and frequently precede life-threatening symptoms such as metabolic decompensation with lactic acidosis (83%), cardiomyopathy (38%), and cardiac arrhythmias (68%). Deletion of exons 3 to 9 is the most common pathogenic variant (39% of alleles). The majority of reported intragenic variants (17 of 27) result in disruption of the reading frame, and no clear genotype-phenotype correlations could be identified for those variants wherein the reading frame is maintained, highlighting instead the variable expressivity of the disease. CONCLUSIONS: Patients with TRMEA frequently experience life-threatening complications that are preceded by common neurological symptoms underscoring the need for pediatric neurologists to be familiar with this condition. Additional work pertaining to disease pathophysiology and potential therapeutics is needed.
Asunto(s)
Arritmias Cardíacas , Encefalopatías Metabólicas , Estudios de Asociación Genética , Adolescente , Arritmias Cardíacas/epidemiología , Arritmias Cardíacas/genética , Arritmias Cardíacas/fisiopatología , Ataxia/epidemiología , Encefalopatías Metabólicas/epidemiología , Encefalopatías Metabólicas/genética , Encefalopatías Metabólicas/fisiopatología , Niño , Preescolar , Estudios de Cohortes , Discapacidades del Desarrollo/epidemiología , Femenino , Humanos , Lactante , Masculino , Prevalencia , Rabdomiólisis/epidemiología , SíndromeRESUMEN
Diamond-Blackfan anemia (DBA) is a rare bone marrow failure syndrome usually caused by heterozygous variants in ribosomal proteins (RP) and which leads to severe anemia. Genetic studies in DBA rely primarily on multigene panels that often result in variants of unknown significance. Our objective was to optimize polysome profiling to functionally validate new large subunit RP variants. We determined the optimal experimental conditions for B-cell polysome profiles then performed this analysis on 2 children with DBA and novel missense RPL5 (uL18) and RPL26 (uL24) variants of unknown significance. Both patients had reduced 60S and 80S fractions when compared with an unaffected parent consistent with a large ribosomal subunit defect. Polysome profiling using primary B-cells is an adjunctive tool that can assist in validation of large subunit RP variants of uncertain significance. Further studies are necessary to validate this method in patients with known DBA mutations, small RP subunit variants, and silent carriers.
Asunto(s)
Anemia de Diamond-Blackfan/genética , Polirribosomas/genética , Proteínas Ribosómicas/genética , Linfocitos B/metabolismo , Preescolar , Femenino , Humanos , Lactante , Masculino , Mutación MissenseRESUMEN
We report three new cases of a germline heterozygous gain-of-function missense (p.(Met1141Lys)) mutation in the C2 domain of phospholipase C gamma 2 (PLCG2) associated with symptoms consistent with previously described auto-inflammation and phospholipase Cγ2 (PLCγ2)-associated antibody deficiency and immune dysregulation (APLAID) syndrome and pediatric common variable immunodeficiency (CVID). Functional evaluation showed platelet hyper-reactivity, increased B cell receptor-triggered calcium influx and ERK phosphorylation. Expression of the altered p.(Met1141Lys) variant in a PLCγ2-knockout DT40 cell line showed clearly enhanced BCR-triggered influx of external calcium when compared to control-transfected cells. Our results further expand the molecular basis of pediatric CVID and phenotypic spectrum of PLCγ2-related defects.
Asunto(s)
Linfocitos B/inmunología , Inmunodeficiencia Variable Común/diagnóstico , Mutación de Línea Germinal/genética , Síndromes de Inmunodeficiencia/diagnóstico , Mutación Missense/genética , Fosfolipasa C gamma/genética , Autoinmunidad/genética , Señalización del Calcio , Línea Celular , Niño , Preescolar , Femenino , Humanos , Lactante , Masculino , Fenotipo , Dominios Proteicos/genéticaRESUMEN
BACKGROUND: As clinical exome sequencing (CES) becomes more common, understanding which patients are most likely to benefit and in what manner is critical for the general pediatrics community to appreciate. METHODS: Five hundred and twenty-three patients referred to the Pediatric Genetics clinic at Michigan Medicine were systematically phenotyped by the presence or absence of abnormalities for 13 body/organ systems by a Clinical Genetics team. All patients then underwent CES. RESULTS: Overall, 30% of patients who underwent CES had an identified pathogenic mutation. The most common phenotypes were developmental delay (83%), neuromuscular system abnormalities (81%), and multiple congenital anomalies (42%). In all, 67% of patients had a variant of uncertain significance (VUS) or gene of uncertain significance (GUS); 23% had no variants reported. There was a significant difference in the average number of body systems affected among these groups (pathogenic 5.89, VUS 6.0, GUS 6.12, and no variant 4.6; P < 0.00001). Representative cases highlight four ways in which CES is changing clinical pediatric practice. CONCLUSIONS: Patients with identified variants are enriched for multiple organ system involvement. Furthermore, our phenotyping provides broad insights into which patients are most likely to benefit from genetics referral and CES and how those results can help guide clinical practice more generally.
Asunto(s)
Anomalías Congénitas/genética , Análisis Mutacional de ADN , Secuenciación del Exoma , Pruebas Genéticas , Mutación , Anomalías Congénitas/diagnóstico , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Humanos , Fenotipo , Valor Predictivo de las Pruebas , Estudios RetrospectivosRESUMEN
OBJECTIVE: Pathogenic variants in KCNB1, encoding the voltage-gated potassium channel KV 2.1, are associated with developmental and epileptic encephalopathy (DEE). Previous functional studies on a limited number of KCNB1 variants indicated a range of molecular mechanisms by which variants affect channel function, including loss of voltage sensitivity, loss of ion selectivity, and reduced cell-surface expression. METHODS: We evaluated a series of 17 KCNB1 variants associated with DEE or other neurodevelopmental disorders (NDDs) to rapidly ascertain channel dysfunction using high-throughput functional assays. Specifically, we investigated the biophysical properties and cell-surface expression of variant KV 2.1 channels expressed in heterologous cells using high-throughput automated electrophysiology and immunocytochemistry-flow cytometry. RESULTS: Pathogenic variants exhibited diverse functional defects, including altered current density and shifts in the voltage dependence of activation and/or inactivation, as homotetramers or when coexpressed with wild-type KV 2.1. Quantification of protein expression also identified variants with reduced total KV 2.1 expression or deficient cell-surface expression. INTERPRETATION: Our study establishes a platform for rapid screening of KV 2.1 functional defects caused by KCNB1 variants associated with DEE and other NDDs. This will aid in establishing KCNB1 variant pathogenicity and the mechanism of dysfunction, which will enable targeted strategies for therapeutic intervention based on molecular phenotype. ANN NEUROL 2019;86:899-912.
Asunto(s)
Variación Genética/genética , Ensayos Analíticos de Alto Rendimiento/métodos , Trastornos del Neurodesarrollo/genética , Canales de Potasio Shab/genética , Secuencia de Aminoácidos , Animales , Células CHO , Cricetinae , Cricetulus , Humanos , Trastornos del Neurodesarrollo/diagnóstico , Estructura Secundaria de Proteína , Canales de Potasio Shab/químicaRESUMEN
De novo truncating mutations in Additional sex combs-like 3 (ASXL3) have been identified in individuals with Bainbridge-Ropers syndrome (BRS), characterized by failure to thrive, global developmental delay, feeding problems, hypotonia, dysmorphic features, profound speech delays and intellectual disability. We identified three novel de novo heterozygous truncating variants distributed across ASXL3, outside the original cluster of ASXL3 mutations previously described for BRS. Primary skin fibroblasts established from a BRS patient were used to investigate the functional impact of pathogenic variants. ASXL3 mRNA transcripts from the mutated allele are prone to nonsense-mediated decay, and expression of ASXL3 is reduced. We found that ASXL3 interacts with BAP1, a hydrolase that removes mono-ubiquitin from histone H2A lysine 119 (H2AK119Ub1) as a component of the Polycomb repressive deubiquitination (PR-DUB) complex. A significant increase in H2AK119Ub1 was observed in ASXL3 patient fibroblasts, highlighting an important functional role for ASXL3 in PR-DUB mediated deubiquitination. Transcriptomes of ASXL3 patient and control fibroblasts were compared to investigate the impact of chromatin changes on transcriptional regulation. Out of 564 significantly differentially expressed genes (DEGs) in ASXL3 patient fibroblasts, 52% were upregulated and 48% downregulated. DEGs were enriched in molecular processes impacting transcriptional regulation, development and proliferation, consistent with the features of BRS. This is the first single gene disorder linked to defects in deubiquitination of H2AK119Ub1 and suggests an important role for dynamic regulation of H2A mono-ubiquitination in transcriptional regulation and the pathophysiology of BRS.
Asunto(s)
Discapacidades del Desarrollo/genética , Insuficiencia de Crecimiento/genética , Histonas/metabolismo , Discapacidad Intelectual/genética , Trastornos del Desarrollo del Lenguaje/genética , Mutación , Factores de Transcripción/metabolismo , Preescolar , Discapacidades del Desarrollo/metabolismo , Discapacidades del Desarrollo/patología , Insuficiencia de Crecimiento/metabolismo , Insuficiencia de Crecimiento/patología , Femenino , Fibroblastos/metabolismo , Fibroblastos/patología , Regulación de la Expresión Génica , Genes Dominantes , Heterocigoto , Histonas/genética , Humanos , Discapacidad Intelectual/metabolismo , Discapacidad Intelectual/patología , Trastornos del Desarrollo del Lenguaje/metabolismo , Trastornos del Desarrollo del Lenguaje/patología , Masculino , Cultivo Primario de Células , Unión Proteica , Síndrome , Factores de Transcripción/genética , Transcriptoma , Proteínas Supresoras de Tumor/genética , Proteínas Supresoras de Tumor/metabolismo , Ubiquitina Tiolesterasa/genética , Ubiquitina Tiolesterasa/metabolismo , UbiquitinaciónRESUMEN
The ability to identify the clinical nature of the recurrent duplication of chromosome 17q12 has been limited by its rarity and the diverse range of phenotypes associated with this genomic change. In order to further define the clinical features of affected patients, detailed clinical information was collected in the largest series to date (30 patients and 2 of their siblings) through a multi-institutional collaborative effort. The majority of patients presented with developmental delays varying from mild to severe. Though dysmorphic features were commonly reported, patients do not have consistent and recognizable features. Cardiac, ophthalmologic, growth, behavioral, and other abnormalities were each present in a subset of patients. The newly associated features potentially resulting from 17q12 duplication include height and weight above the 95th percentile, cataracts, microphthalmia, coloboma, astigmatism, tracheomalacia, cutaneous mosaicism, pectus excavatum, scoliosis, hypermobility, hypospadias, diverticulum of Kommerell, pyloric stenosis, and pseudohypoparathryoidism. The majority of duplications were inherited with some carrier parents reporting learning disabilities or microcephaly. We identified additional, potentially contributory copy number changes in a subset of patients, including one patient each with 16p11.2 deletion and 15q13.3 deletion. Our data further define and expand the clinical spectrum associated with duplications of 17q12 and provide support for the role of genomic modifiers contributing to phenotypic variability.
Asunto(s)
Anomalías Múltiples/genética , Duplicación Cromosómica , Adolescente , Niño , Preescolar , Variaciones en el Número de Copia de ADN , Discapacidades del Desarrollo/genética , Cara/anomalías , Femenino , Humanos , Lactante , Masculino , Microcefalia/genética , Fenotipo , Adulto JovenRESUMEN
We describe the molecular and clinical characterization of nine individuals with recurrent, 3.4-Mb, de novo deletions of 3q13.2-q13.31 detected by chromosomal microarray analysis. All individuals have hypotonia and language and motor delays; they variably express mild to moderate cognitive delays (8/9), abnormal behavior (7/9), and autism spectrum disorders (3/9). Common facial features include downslanting palpebral fissures with epicanthal folds, a slightly bulbous nose, and relative macrocephaly. Twenty-eight genes map to the deleted region, including four strong candidate genes, DRD3, ZBTB20, GAP43, and BOC, with important roles in neural and/or muscular development. Analysis of the breakpoint regions based on array data revealed directly oriented human endogenous retrovirus (HERV-H) elements of ~5 kb in size and of >95% DNA sequence identity flanking the deletion. Subsequent DNA sequencing revealed different deletion breakpoints and suggested nonallelic homologous recombination (NAHR) between HERV-H elements as a mechanism of deletion formation, analogous to HERV-I-flanked and NAHR-mediated AZFa deletions. We propose that similar HERV elements may also mediate other recurrent deletion and duplication events on a genome-wide scale. Observation of rare recurrent chromosomal events such as these deletions helps to further the understanding of mechanisms behind naturally occurring variation in the human genome and its contribution to genetic disease.
Asunto(s)
Deleción Cromosómica , Cromosomas Humanos Par 3/genética , Trastornos del Conocimiento/genética , Discapacidades del Desarrollo/genética , Retrovirus Endógenos/genética , Hipotonía Muscular/genética , Adolescente , Adulto , Secuencia de Bases , Niño , Preescolar , Puntos de Rotura del Cromosoma , Trastornos del Conocimiento/diagnóstico , Hibridación Genómica Comparativa , Discapacidades del Desarrollo/diagnóstico , Facies , Femenino , Orden Génico , Humanos , Lactante , Masculino , Datos de Secuencia Molecular , Hipotonía Muscular/diagnóstico , Fenotipo , Alineación de Secuencia , Síndrome , Adulto JovenRESUMEN
Deletions at 2p16.3 involving exons of NRXN1 are associated with susceptibility for autism and schizophrenia, and similar deletions have been identified in individuals with developmental delay and dysmorphic features. We have identified 34 probands with exonic NRXN1 deletions following referral for clinical microarray-based comparative genomic hybridization. To more firmly establish the full phenotypic spectrum associated with exonic NRXN1 deletions, we report the clinical features of 27 individuals with NRXN1 deletions, who represent 23 of these 34 families. The frequency of exonic NRXN1 deletions among our postnatally diagnosed patients (0.11%) is significantly higher than the frequency among reported controls (0.02%; P = 6.08 × 10(-7) ), supporting a role for these deletions in the development of abnormal phenotypes. Generally, most individuals with NRXN1 exonic deletions have developmental delay (particularly speech), abnormal behaviors, and mild dysmorphic features. In our cohort, autism spectrum disorders were diagnosed in 43% (10/23), and 16% (4/25) had epilepsy. The presence of NRXN1 deletions in normal parents and siblings suggests reduced penetrance and/or variable expressivity, which may be influenced by genetic, environmental, and/or stochastic factors. The pathogenicity of these deletions may also be affected by the location of the deletion within the gene. Counseling should appropriately represent this spectrum of possibilities when discussing recurrence risks or expectations for a child found to have a deletion in NRXN1.
Asunto(s)
Moléculas de Adhesión Celular Neuronal/genética , Eliminación de Gen , Proteínas del Tejido Nervioso/genética , Anomalías Múltiples/diagnóstico , Anomalías Múltiples/genética , Adolescente , Adulto , Trastorno Autístico/genética , Proteínas de Unión al Calcio , Niño , Preescolar , Hibridación Genómica Comparativa , Discapacidades del Desarrollo/genética , Exones , Facies , Femenino , Interacción Gen-Ambiente , Estudio de Asociación del Genoma Completo , Humanos , Lactante , Discapacidad Intelectual/genética , Masculino , Persona de Mediana Edad , Moléculas de Adhesión de Célula Nerviosa , Penetrancia , Fenotipo , Esquizofrenia/genética , Adulto JovenRESUMEN
BACKGROUND: Chromosome 15q24 microdeletion syndrome is a rare genomic disorder characterised by intellectual disability, growth retardation, unusual facial morphology and other anomalies. To date, 20 patients have been reported; 18 have had detailed breakpoint analysis. AIM: To further delineate the features of the 15q24 microdeletion syndrome, the clinical and molecular characterisation of fifteen patients with deletions in the 15q24 region was performed, nearly doubling the number of reported patients. METHODS: Breakpoints were characterised using a custom, high-density array comparative hybridisation platform, and detailed phenotype information was collected for each patient. RESULTS: Nine distinct deletions with different breakpoints ranging in size from 266 kb to 3.75 Mb were identified. The majority of breakpoints lie within segmental duplication (SD) blocks. Low sequence identity and large intervals of unique sequence between SD blocks likely contribute to the rarity of 15q24 deletions, which occur 8-10 times less frequently than 1q21 or 15q13 microdeletions in our series. Two small, atypical deletions were identified within the region that help delineate the critical region for the core phenotype in the 15q24 microdeletion syndrome. CONCLUSION: The molecular characterisation of these patients suggests that the core cognitive features of the 15q24 microdeletion syndrome, including developmental delays and severe speech problems, are largely due to deletion of genes in a 1.1-Mb critical region. However, genes just distal to the critical region also play an important role in cognition and in the development of characteristic facial features associated with 15q24 deletions. Clearly, deletions in the 15q24 region are variable in size and extent. Knowledge of the breakpoints and size of deletion combined with the natural history and medical problems of our patients provide insights that will inform management guidelines. Based on common phenotypic features, all patients with 15q24 microdeletions should receive a thorough neurodevelopmental evaluation, physical, occupational and speech therapies, and regular audiologic and ophthalmologic screening.
Asunto(s)
Anomalías Múltiples/genética , Deleción Cromosómica , Cromosomas Humanos Par 15 , Discapacidades del Desarrollo/genética , Anomalías Múltiples/diagnóstico , Secuencia de Bases , Puntos de Rotura del Cromosoma , Hibridación Genómica Comparativa , Discapacidades del Desarrollo/diagnóstico , Facies , Femenino , Estudios de Asociación Genética , Humanos , Masculino , Datos de Secuencia Molecular , Duplicaciones Segmentarias en el Genoma , SíndromeRESUMEN
Kabuki syndrome is a rare, multiple malformation disorder characterized by a distinctive facial appearance, cardiac anomalies, skeletal abnormalities, and mild to moderate intellectual disability. Simplex cases make up the vast majority of the reported cases with Kabuki syndrome, but parent-to-child transmission in more than a half-dozen instances indicates that it is an autosomal dominant disorder. We recently reported that Kabuki syndrome is caused by mutations in MLL2, a gene that encodes a Trithorax-group histone methyltransferase, a protein important in the epigenetic control of active chromatin states. Here, we report on the screening of 110 families with Kabuki syndrome. MLL2 mutations were found in 81/110 (74%) of families. In simplex cases for which DNA was available from both parents, 25 mutations were confirmed to be de novo, while a transmitted MLL2 mutation was found in two of three familial cases. The majority of variants found to cause Kabuki syndrome were novel nonsense or frameshift mutations that are predicted to result in haploinsufficiency. The clinical characteristics of MLL2 mutation-positive cases did not differ significantly from MLL2 mutation-negative cases with the exception that renal anomalies were more common in MLL2 mutation-positive cases. These results are important for understanding the phenotypic consequences of MLL2 mutations for individuals and their families as well as for providing a basis for the identification of additional genes for Kabuki syndrome.
Asunto(s)
Anomalías Múltiples/genética , Proteínas de Unión al ADN/genética , Enfermedades Hematológicas/genética , Mutación/genética , Proteínas de Neoplasias/genética , Enfermedades Vestibulares/genética , Anomalías Múltiples/diagnóstico , Alelos , Cara/anomalías , Orden Génico , Pruebas Genéticas , Genotipo , Enfermedades Hematológicas/diagnóstico , Humanos , Fenotipo , Pronóstico , Enfermedades Vestibulares/diagnósticoRESUMEN
X-linked intestinal pseudo-obstruction, a rare disorder caused by mutations in FLNA, the gene encoding the cytoskeletal protein filamin A, has been regarded as a hereditary enteric neuropathy largely on the basis of sparse and incomplete pathologic studies. Diffuse abnormal layering of small intestinal smooth muscle (DAL) is a rare malformation, which has only been described in 4 patients (all male, 3 in the same family) with intestinal pseudo-obstruction. We report DAL in 5 male patients (2 families) with intestinal pseudo-obstruction and mutations in FLNA. Light microscopic, ultrastructural, and immunohistochemical studies showed abnormal lamination of the small intestinal muscularis propria with associated absent or severely reduced FLNA immunoreactivity. Intestinal samples from the oldest patient in the series, a teenager, showed multinucleate myocytes in small and large intestine, along the submucosal surface of the muscularis propria. As neither DAL nor the pattern of myocyte multinucleation observed in our patients have been described outside the context of X-linked intestinal pseudo-obstruction, these histopathologic features may be specific for this hereditary disorder and suggest an underlying myopathic basis for dysmotility in affected patients.
Asunto(s)
Proteínas Contráctiles/genética , Enfermedades Genéticas Ligadas al Cromosoma X/genética , Seudoobstrucción Intestinal/genética , Intestino Delgado/anomalías , Proteínas de Microfilamentos/genética , Músculo Liso/anomalías , Mutación , Adolescente , Niño , Proteínas Contráctiles/metabolismo , Femenino , Filaminas , Enfermedades Genéticas Ligadas al Cromosoma X/metabolismo , Enfermedades Genéticas Ligadas al Cromosoma X/patología , Humanos , Recién Nacido , Seudoobstrucción Intestinal/metabolismo , Seudoobstrucción Intestinal/patología , Intestino Grueso/patología , Intestino Delgado/metabolismo , Masculino , Proteínas de Microfilamentos/metabolismo , Membrana Mucosa/anomalías , Membrana Mucosa/metabolismo , Músculo Liso/metabolismo , Miocitos del Músculo Liso/metabolismo , Miocitos del Músculo Liso/patología , LinajeRESUMEN
We demonstrate the successful application of exome sequencing to discover a gene for an autosomal dominant disorder, Kabuki syndrome (OMIM%147920). We subjected the exomes of ten unrelated probands to massively parallel sequencing. After filtering against existing SNP databases, there was no compelling candidate gene containing previously unknown variants in all affected individuals. Less stringent filtering criteria allowed for the presence of modest genetic heterogeneity or missing data but also identified multiple candidate genes. However, genotypic and phenotypic stratification highlighted MLL2, which encodes a Trithorax-group histone methyltransferase: seven probands had newly identified nonsense or frameshift mutations in this gene. Follow-up Sanger sequencing detected MLL2 mutations in two of the three remaining individuals with Kabuki syndrome (cases) and in 26 of 43 additional cases. In families where parental DNA was available, the mutation was confirmed to be de novo (n = 12) or transmitted (n = 2) in concordance with phenotype. Our results strongly suggest that mutations in MLL2 are a major cause of Kabuki syndrome.
Asunto(s)
Anomalías Múltiples/genética , Proteínas de Unión al ADN/genética , Mutación , Proteínas de Neoplasias/genética , Análisis de Secuencia de ADN/métodos , Frecuencia de los Genes , Ligamiento Genético , Predisposición Genética a la Enfermedad , Humanos , Mutación/fisiología , Polimorfismo de Nucleótido Simple , Síndrome , Estudios de Validación como AsuntoRESUMEN
AIMS: Transforming growth factor-ß (TGF-ß) signaling is critical for the differentiation of smooth muscle cells (SMCs) into quiescent cells expressing a full repertoire of contractile proteins. Heterozygous mutations in TGF-ß receptor type II (TGFBR2) disrupt TGF-ß signaling and lead to genetic conditions that predispose to thoracic aortic aneurysms and dissections (TAADs). The aim of this study is to determine the molecular mechanism by which TGFBR2 mutations cause TAADs. METHODS AND RESULTS: Using aortic SMCs explanted from patients with TGFBR2 mutations, we show decreased expression of SMC contractile proteins compared with controls. Exposure to TGF-ß1 fails to increase expression of contractile genes in mutant SMCs, whereas control cells further increase expression of these genes. Analysis of fixed and frozen aortas from patients with TGFBR2 mutations confirms decreased in vivo expression of contractile proteins relative to unaffected aortas. Fibroblasts explanted from patients with TGFBR2 mutations fail to transform into mature myofibroblasts with TGF-ß1 stimulation as assessed by expression of contractile proteins. CONCLUSIONS: These data support the conclusion that heterozygous TGFBR2 mutations lead to decreased expression of SMC contractile protein in both SMCs and myofibroblasts. The failure of TGFBR2-mutant SMCs to fully express SMC contractile proteins predicts defective contractile function in these cells and aligns with a hypothesis that defective SMC contractile function contributes to the pathogenesis of TAAD.
Asunto(s)
Aneurisma de la Aorta Torácica/genética , Disección Aórtica/genética , Diferenciación Celular/genética , Predisposición Genética a la Enfermedad/genética , Músculo Liso Vascular/citología , Miofibroblastos/citología , Proteínas Serina-Treonina Quinasas/genética , Receptores de Factores de Crecimiento Transformadores beta/genética , Actinas/metabolismo , Disección Aórtica/metabolismo , Animales , Aneurisma de la Aorta Torácica/metabolismo , Proteínas de Unión al Calcio/metabolismo , Proteínas de Unión a Calmodulina/metabolismo , Estudios de Casos y Controles , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/fisiología , Línea Celular , Proliferación Celular , Células Cultivadas , Humanos , Ratones , Proteínas de Microfilamentos/metabolismo , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/metabolismo , Miofibroblastos/metabolismo , Fenotipo , Proteínas Serina-Treonina Quinasas/metabolismo , Receptor Tipo II de Factor de Crecimiento Transformador beta , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Transducción de Señal/fisiología , Transfección , Factor de Crecimiento Transformador beta1/farmacología , CalponinasRESUMEN
BACKGROUND: Septins are involved in a number of cellular processes including cytokinesis and organization of the cytoskeleton. Alterations in human septin-9 (SEPT9) levels have been linked to multiple cancers, whereas mutations in SEPT9 cause the episodic neuropathy, hereditary neuralgic amyotrophy (HNA). Despite its important function in human health, the in vivo role of SEPT9 is unknown. METHODOLOGY/PRINCIPAL FINDINGS: Here we utilize zebrafish to study the role of SEPT9 in early development. We show that zebrafish possess two genes, sept9a and sept9b that, like humans, express multiple transcripts. Knockdown or overexpression of sept9a transcripts results in specific developmental alterations including circulation defects and aberrant epidermal development. CONCLUSIONS/SIGNIFICANCE: Our work demonstrates that sept9 plays an important role in zebrafish development, and establishes zebrafish as a valuable model organism for the study of SEPT9.
Asunto(s)
Empalme Alternativo/genética , Regulación del Desarrollo de la Expresión Génica , Proteínas de Pez Cebra/genética , Pez Cebra/embriología , Pez Cebra/genética , Secuencia de Aminoácidos , Animales , Muerte Celular , Secuencia Conservada/genética , Embrión no Mamífero/metabolismo , Técnicas de Silenciamiento del Gen , Datos de Secuencia Molecular , ARN Mensajero/genética , ARN Mensajero/metabolismo , Proteínas de Pez Cebra/antagonistas & inhibidores , Proteínas de Pez Cebra/química , Proteínas de Pez Cebra/metabolismoRESUMEN
Hypotonia is characterized by reduced resistance to passive range of motion in joints versus weakness, which is a reduction in the maximum muscle power that can be generated. (Dubowitz, 1985; Crawford, 1992; Martin, 2005) Based on strong research evidence, central hypotonia accounts for 60% to 80% of cases of hypotonia, whereas peripheral hypotonia is the cause in about 15% to 30% of cases. Disorders causing hypotonia often are associated with a depressed level of consciousness, predominantly axial weakness, normal strength accompanying the hypotonia, and hyperactive or normal reflexes. (Martin, 2005; Igarashi, 2004; Richer, 2001; Miller, 1992; Crawford, 1992; Bergen, 1985; Dubowitz, 1985) Based on some research evidence, 50% of patients who have hypotonia are diagnosed by history and physical examination alone. (Paro-Panjan, 2004) Based on some research evidence, an appropriate medical and genetic evaluation of hypotonia in infants includes a karyotype, DNA-based diagnostic tests, and cranial imaging. (Battaglia, 2008; Laugel, 2008; Birdi, 2005; Paro-Panjan, 2004; Prasad, 2003; Richer, 2001; Dimario, 1989) Based on strong research evidence, infant botulism should be suspected in an acute or subacute presentation of hypotonia in an infant younger than 6 months of age who has signs and symptoms such as constipation, listlessness, poor feeding, weak cry, and a decreased gag reflex. (Francisco, 2007; Muensterer, 2000)