RESUMEN
The TSC1 and TSC2 gene products interact to form the tuberous sclerosis complex (TSC), an important negative regulator of the mechanistic target of rapamycin complex 1 (TORC1). Inactivating mutations in TSC1 or TSC2 cause TSC, and the identification of a pathogenic TSC1 or TSC2 variant helps establish a diagnosis of TSC. However, it is not always clear whether TSC1 and TSC2 variants are inactivating. To determine whether TSC1 and TSC2 variants of uncertain clinical significance affect TSC complex function and cause TSC, in vitro assays of TORC1 activity can be employed. Here we combine genetic, functional, and structural approaches to try and classify a series of 15 TSC2 VUS. We investigated the effects of the variants on the formation of the TSC complex, on TORC1 activity and on TSC2 pre-mRNA splicing. In 13 cases (87%), the functional data supported the hypothesis that the identified TSC2 variant caused TSC. Our results illustrate the benefits and limitations of functional testing for TSC.
Asunto(s)
Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Mutación , Fenotipo , Proteína 2 del Complejo de la Esclerosis Tuberosa/química , Proteína 2 del Complejo de la Esclerosis Tuberosa/genética , Sustitución de Aminoácidos , Técnicas de Silenciamiento del Gen , Estudios de Asociación Genética/métodos , Genotipo , Humanos , Modelos Moleculares , Unión Proteica , Conformación Proteica , Multimerización de Proteína , Empalme del ARN , Relación Estructura-Actividad , Proteína 2 del Complejo de la Esclerosis Tuberosa/metabolismoRESUMEN
[This corrects the article DOI: 10.1371/journal.pone.0091952.].
RESUMEN
BACKGROUND: The bladder exstrophy-epispadias complex (BEEC) represents the severe end of the congenital uro-rectal malformation spectrum. Initial studies have implicated rare copy number variations (CNVs), including recurrent duplications of chromosomal region 22q11.21, in BEEC etiology. METHODS: To detect further CNVs, array analysis was performed in 169 BEEC patients. Prior to inclusion, 22q11.21 duplications were excluded using multiplex ligation-dependent probe amplification. RESULTS: Following the application of stringent filter criteria, seven rare CNVs were identified: n = 4, not present in 1307 in-house controls; n = 3, frequency of <0.002 in controls. These CNVs ranged from 1 to 6.08 Mb in size. To identify smaller CNVs, relaxed filter criteria used in the detection of previously reported BEEC associated chromosomal regions were applied. This resulted in the identification of six additional rare CNVs: n = 4, not present in 1307 in-house controls; n = 2, frequency <0.0008 in controls. These CNVs ranged from 0.03-0.08 Mb in size. For 10 of these 13 CNVs, confirmation and segregation analyses were performed (5 of maternal origin; 5 of paternal origin). Interestingly, one female with classic bladder extrophy carried a 1.18 Mb duplication of 22q11.1, a chromosomal region that is associated with cat eye syndrome. CONCLUSIONS: A number of rare CNVs were identified in BEEC patients, and these represent candidates for further evaluation. Rare inherited CNVs may constitute modifiers of, or contributors to, multifactorial BEEC phenotypes.
Asunto(s)
Extrofia de la Vejiga/genética , Análisis Citogenético/métodos , Variaciones en el Número de Copia de ADN , Análisis de Secuencia por Matrices de Oligonucleótidos/métodos , Aneuploidia , Trastornos de los Cromosomas/genética , Duplicación Cromosómica , Cromosomas Humanos Par 22/genética , Anomalías del Ojo/genética , Femenino , Humanos , Masculino , Herencia Materna , Herencia PaternaRESUMEN
Inactivating mutations in TSC1 and TSC2 cause tuberous sclerosis complex (TSC). The 2012 international consensus meeting on TSC diagnosis and management agreed that the identification of a pathogenic TSC1 or TSC2 variant establishes a diagnosis of TSC, even in the absence of clinical signs. However, exons 25 and 31 of TSC2 are subject to alternative splicing. No variants causing clinically diagnosed TSC have been reported in these exons, raising the possibility that such variants would not cause TSC. We present truncating and in-frame variants in exons 25 and 31 in three individuals unlikely to fulfil TSC diagnostic criteria and examine the importance of these exons in TSC using different approaches. Amino acid conservation analysis suggests significantly less conservation in these exons compared with the majority of TSC2 exons, and TSC2 expression data demonstrates that the majority of TSC2 transcripts lack exons 25 and/or 31 in many human adult tissues. In vitro assay of both exons shows that neither exon is essential for TSC complex function. Our evidence suggests that variants in TSC2 exons 25 or 31 are very unlikely to cause classical TSC, although a role for these exons in tissue/stage specific development cannot be excluded.
Asunto(s)
Exones , Estudios de Asociación Genética , Mutación , Esclerosis Tuberosa/diagnóstico , Esclerosis Tuberosa/genética , Proteínas Supresoras de Tumor/genética , Adulto , Alelos , Empalme Alternativo , Niño , Preescolar , Biología Computacional/métodos , Bases de Datos Genéticas , Expresión Génica , Variación Genética , Humanos , Fenotipo , Proteína 2 del Complejo de la Esclerosis TuberosaRESUMEN
Germline and somatic biallelic mutations of the Tuberous sclerosis complex (TSC) 1 and TSC2 gene products cause TSC, an autosomal dominant multifocal hamartomatosis with variable neurological manifestations. The consequences of TSC1 or TSC2 loss in cells of hematopoietic origin have recently started to be unveiled in mice and showed to hinder the development of proper T cell immunity. To date, the consequences of germline TSC1 mutations and/or its loss in mature human T cells remain to be determined. To address these issues, we analyzed subset representation, phenotype and responsiveness to mitogens in T cells from patients with inherited monoallelic TSC1 mutations, and induced shRNA-mediated TSC1 down-regulation in primary and transformed human T cells. We report that, the distribution of peripheral CD4 and CD8 T cell subsets, their cytokine-secretion profile, and responsiveness to in vitro stimulation were largely preserved in TSC subjects with monoallelic TSC1 germline mutations when compared to healthy controls. Sufficient levels of hamartin and tuberin and proper control of mTOR-dependent signaling in primary T cells from TSC subjects best explained this. In contrast, shRNA-induced down-regulation of TSC1, likely mimicking biallelic inactivation of TSC1, compromised hamartin and tuberin expression and mTORC2/AKT/FoxO1/3 signaling causing both primary and transformed T cells to die by apoptosis. Thus, our results indicate that, while one functional TSC1 allele preserves human T lymphocytes development and homeostasis, TSC1 acute down-regulation is detrimental to the survival of both primary and transformed T cells.
Asunto(s)
Alelos , Mutación de Línea Germinal , Homeostasis , Subgrupos de Linfocitos T/citología , Esclerosis Tuberosa/genética , Esclerosis Tuberosa/inmunología , Proteínas Supresoras de Tumor/genética , Adulto , Animales , Apoptosis/genética , Proliferación Celular , Supervivencia Celular/genética , Regulación hacia Abajo/genética , Proteína Forkhead Box O1 , Factores de Transcripción Forkhead/metabolismo , Silenciador del Gen , Humanos , Ratones , Persona de Mediana Edad , Mitocondrias/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , ARN Interferente Pequeño/genética , Transducción de Señal , Serina-Treonina Quinasas TOR/metabolismo , Proteína 1 del Complejo de la Esclerosis Tuberosa , Proteínas Supresoras de Tumor/deficienciaRESUMEN
We report on a newborn boy with a bilateral cleft of the primary palate, duplicated triphalangeal thumbs, and a patent foramen ovale. During childhood he had moderate developmental delay. Brain MRI at 4 years was normal. The concurrence of non-syndromic clefts of the lip/palate (CL/P) and duplicated thumbs with triphalangeal component has, to our knowledge, not been reported so far. In our case, array-CGH analysis documented two de novo deletions (â¼1.2 Mb and â¼400 Kb) of the long arm of chromosome 4, containing four genes: platelet-derived growth factor C (PDGFC), glycine receptor beta subunit (GLRB), glutamate receptor ionotropic AMPA2 (GRIA2), and F-box protein 8 gene (FBXO8). PDGFC codes for a mesenchymal cell growth factor already known to be associated with clefts of the lip. Pdgfc(-/-) mice have skeletal anomalies, and facial schisis resembling human cleft/lip palate. GRIA2 codes for a ligand-activated cation channel that mediates the fast component of postsynaptic excitatory currents in neurons, and may be linked to cognitive dysfunction. FBXO8, a gene of unknown function, is a member of the F-box gene family, among which FBXW4, within the minimal duplicated region associated with human split-hand/foot malformation type 3 (SHFM type 3). The presence of overlapping deletions in patients who do not share the same phenotype of our case suggests incomplete penetrance, and a possible effect of modifier genetic factors.
Asunto(s)
Deleción Cromosómica , Cromosomas Humanos Par 4 , Labio Leporino/genética , Deformidades Congénitas de la Mano/genética , Pulgar/anomalías , Anomalías Múltiples/diagnóstico , Anomalías Múltiples/genética , Animales , Labio Leporino/diagnóstico , Hibridación Genómica Comparativa , Deformidades Congénitas de la Mano/diagnóstico , Humanos , Recién Nacido , Linfocinas/genética , Masculino , Ratones , Linaje , Fenotipo , Factor de Crecimiento Derivado de Plaquetas/genética , Receptores AMPA/genética , SíndromeRESUMEN
Spinocerebellar ataxia type 28 is an autosomal dominant form of cerebellar ataxia (ADCA) caused by mutations in AFG3L2, a gene that encodes a subunit of the mitochondrial m-AAA protease. We screened 366 primarily Caucasian ADCA families, negative for the most common triplet expansions, for point mutations in AFG3L2 using DHPLC. Whole-gene deletions were excluded in 300 of the patients, and duplications were excluded in 129 patients. We found six missense mutations in nine unrelated index cases (9/366, 2.6%): c.1961C>T (p.Thr654Ile) in exon 15, c.1996A>G (p.Met666Val), c.1997T>G (p.Met666Arg), c.1997T>C (p.Met666Thr), c.2011G>A (p.Gly671Arg), and c.2012G>A (p.Gly671Glu) in exon 16. All mutated amino acids were located in the C-terminal proteolytic domain. In available cases, we demonstrated the mutations segregated with the disease. Mutated amino acids are highly conserved, and bioinformatic analysis indicates the substitutions are likely deleterious. This investigation demonstrates that SCA28 accounts for â¼3% of ADCA Caucasian cases negative for triplet expansions and, in extenso, to â¼1.5% of all ADCA. We further confirm both the involvement of AFG3L2 gene in SCA28 and the presence of a mutational hotspot in exons 15-16. Screening for SCA28, is warranted in patients who test negative for more common SCAs and present with a slowly progressive cerebellar ataxia accompanied by oculomotor signs.
Asunto(s)
Proteasas ATP-Dependientes/genética , Ataxia Cerebelosa/epidemiología , Mutación Missense , Proteasas ATP-Dependientes/química , ATPasas Asociadas con Actividades Celulares Diversas , Adolescente , Adulto , Anciano , Ataxia Cerebelosa/etnología , Ataxia Cerebelosa/genética , Ataxia Cerebelosa/patología , Niño , Preescolar , Biología Computacional , Europa (Continente)/epidemiología , Femenino , Genes Dominantes , Humanos , Lactante , Masculino , Persona de Mediana Edad , Modelos Moleculares , Linaje , Prevalencia , Ataxias Espinocerebelosas/congénito , Degeneraciones Espinocerebelosas/epidemiología , Degeneraciones Espinocerebelosas/etnología , Degeneraciones Espinocerebelosas/genética , Degeneraciones Espinocerebelosas/patología , Población Blanca , Adulto JovenRESUMEN
SCA12 is an autosomal dominant cerebellar ataxia characterized by onset in the fourth decade of life with action tremor of arms and head, mild ataxia, dysmetria, and hyperreflexia. The disease is caused by an expansion of >or=51 CAGs in the 5' region of the brain- specific phosphatase 2 regulatory subunit B-beta isoform (PPP2R2B) gene. SCA12 is very rare, except for a single ethnic group in India. We screened 159 Italian ataxic patients for SCA12 and identified two families that segregated an expanded allele of 57 to 58 CAGs, sharing a common haplotype. The age at onset, phenotype, and variability of symptoms were compatible with known cases. In one family, the disease was apparently sporadic due to possible incomplete penetrance and/or late age at onset. Our data indicate that SCA12 is also present in Italian patients, and its genetic testing should be applied to both sporadic and familial ataxias.
Asunto(s)
Ataxia/fisiopatología , Proteínas del Tejido Nervioso/genética , Proteína Fosfatasa 2/genética , Ataxias Espinocerebelosas/diagnóstico , Expansión de Repetición de Trinucleótido/genética , Adolescente , Adulto , Anciano , Salud de la Familia , Femenino , Humanos , Italia , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Tomografía de Emisión de Positrones/métodos , Protones , Estudios Retrospectivos , Ataxias Espinocerebelosas/genética , Adulto JovenRESUMEN
Ataxia is a frequently reported symptom in prion diseases (PD) and it is characteristic of Gerstmann-Sträussler-Scheinker syndrome (GSS), a genetic PD mainly related to the P102L mutation in the PRNP gene. Our aim was to screen for the P102L and other six known PRNP gene mutations (P105L, A117V, Y145X, E200K, D202N, and V210I) a group of 206 consecutive patients diagnosed with adult-onset cerebellar ataxia of unknown origin. The patients, negative for the most common acquired and genetic forms, were analyzed using a combination of restriction endonuclease digestion and pyrosequencing; eight, affected by ataxia and cognitive dysfunction, were also sequenced for the PRNP gene. One patient resulted to be heterozygous for the P102L mutation. Retrospectively, the clinical picture was consistent with a "classical" GSS phenotype. In conclusion, the screening for the P102L mutation, or even the sequencing of the PRNP gene should be taken in consideration in patients with late-onset ataxia (>50 years).
Asunto(s)
Ataxia Cerebelosa/etiología , Enfermedad de Gerstmann-Straussler-Scheinker/diagnóstico , Mutación Missense , Mutación Puntual , Priones/genética , Adulto , Edad de Inicio , Anciano , Ataxia Cerebelosa/epidemiología , Femenino , Pruebas Genéticas , Enfermedad de Gerstmann-Straussler-Scheinker/complicaciones , Enfermedad de Gerstmann-Straussler-Scheinker/genética , Humanos , Italia/epidemiología , Masculino , Persona de Mediana Edad , Proteínas PriónicasRESUMEN
Mutation detection remains problematic for large genes, primarily because PCR-based methodology fails to detect heterozygous deletions and any duplication. In the ATM gene only a handful of multi-exon deletions have been described to date, and this type of mutation has been considered rare. To address this issue we tested a new MLPA (Multiplex Ligation Probe Amplification) kit that covers 33 of the 66 ATM exons, using for controls two previously characterized genomic deletions in addition to three A-T patients, taken from a survey of nine, who had missing four mutations unidentified after conventional mutation screening. We identified for the first time: 1) a approximately 41 kb genomic duplication spanning exons 4-20 (c.-30_2816dup41kb)(a.k.a., ATM dup 41 kb); 2) a novel genomic deletion including exon 31, and 3) in hemizygosis a point mutation in the non-deleted exon 31. In this study we extended mutation detection to nine new Italian A-T patients, using a combined approach of haplotype analysis, DHPLC and MLPA. Overall we achieved a mutation detection rate of >97%, and can now define a spectrum of ATM mutations based on twenty-one consecutive Italian families with A-T.
Asunto(s)
Proteínas de Ciclo Celular/genética , Proteínas de Unión al ADN/genética , Exones , Duplicación de Gen , Mutación , Técnicas de Amplificación de Ácido Nucleico/métodos , Proteínas Serina-Treonina Quinasas/genética , Proteínas Supresoras de Tumor/genética , Proteínas de la Ataxia Telangiectasia Mutada , Estudios de Casos y Controles , Cromatografía Líquida de Alta Presión , ADN/genética , ADN/aislamiento & purificación , Eliminación de Gen , Marcadores Genéticos , Haplotipos , Humanos , Linaje , Mutación Puntual , Polimorfismo de Nucleótido Simple , Secuencias Repetidas en TándemRESUMEN
Hemimegalencephaly is a rare brain malformation consisting of the enlargement of 1 hemisphere, often associated with abnormal cortical gyration, thick cortex, large neurons, and increased astrocytes. Cranial asymmetry is the first clinical sign usually present at birth; in the most severe cases, hemimegalencephaly may be evident during pregnancy. Hemiparesis, intractable epilepsy, and developmental delay are the typical clinical manifestations. Tuberous Sclerosis Complex is an autosomal dominant disorder affecting about 1 in 6000 live births; the number of spontaneous mutations is remarkable. It is characterized by the development of hamartias, or nongrowing lesions, and hamartomas, which grow as benign tumors and rarely progress to malignancy. These lesions most frequently involve the brain, skin, kidneys, eyes, and heart. The rare association of hemimegalencephaly and tuberous sclerosis complex has been reported in a few cases. The authors report the case of a 4-year-old boy with left hemimegalencephaly, tuberous sclerosis complex genetically confirmed, and intractable epilepsy originating from the nonhemimegalencephalic hemisphere.
Asunto(s)
Epilepsia/etiología , Lateralidad Funcional/fisiología , Malformaciones del Sistema Nervioso/complicaciones , Esclerosis Tuberosa/complicaciones , Preescolar , Progresión de la Enfermedad , Electroencefalografía/métodos , Epilepsia/patología , Humanos , Imagen por Resonancia Magnética , Masculino , Malformaciones del Sistema Nervioso/patología , Esclerosis Tuberosa/patologíaRESUMEN
In patients affected by Ataxia-Telangiectasia (A-T), mutations in the ATM gene lead to loss-of-function alleles. Nonsense, splice-site variants, small insertions or deletions (frameshifts) and missense are the most commonly found mutations. Large genomic deletions (LGDs) are rare (approximately 1%) but can lead to the same phenotype. In compound heterozygotes, deletions are not detected by most screening strategies. We analysed the ATM gene in 12 unrelated Italian A-T patients and identified all 24 mutated alleles. Twelve mutations were novel. Standardized SNP and STR haplotyping followed by DHPLC screening of genomic DNA, allowed all but three mutations to be detected (approximately 87.5%). The remaining mutations required RT-PCR analysis of ATM transcript and Southern blotting of genomic DNA. We found three LGDs: one of 8.5 and two identical of 18 kb spanning exons 32-36 and 21-29, respectively. The breakpoints of these deletions were sequenced in an attempt to understand the mechanisms of mutations; both deletions involved regions rich in repeated elements.
Asunto(s)
Ataxia Telangiectasia/genética , Proteínas de Ciclo Celular/genética , Proteínas de Unión al ADN/genética , Mutación/genética , Proteínas Serina-Treonina Quinasas/genética , Proteínas Supresoras de Tumor/genética , Ataxia Telangiectasia/etnología , Proteínas de la Ataxia Telangiectasia Mutada , Secuencia de Bases , Southern Blotting , Cromatografía Líquida de Alta Presión/métodos , Análisis Mutacional de ADN/métodos , Exones/genética , Salud de la Familia , Femenino , Eliminación de Gen , Haplotipos/genética , Humanos , Italia , Masculino , Modelos Genéticos , Datos de Secuencia Molecular , Polimorfismo Genético , Homología de Secuencia de Ácido Nucleico , Programas InformáticosRESUMEN
Large expansions in the SCA2 and SCA7 genes (>100 CAG repeats) have been associated with juvenile and infantile forms of cerebellar ataxias that cannot be detected using standard polymerase chain reaction (PCR). Here, we describe a successful application of the fluorescent short tandem repeat-primed PCR method for accurate identification of these expanded repeats. The test is robust, reliable, and inexpensive and can be used to screen large series of patients, although it cannot give a precise evaluation of the size of the expansion. This test may be of practical value in prenatal diagnoses offered to affected or pre-symptomatic at-risk parents, in which a very large expansion inherited from one of the parents can be missed in the fetus by standard PCR.
Asunto(s)
Proteínas del Tejido Nervioso/genética , Reacción en Cadena de la Polimerasa/métodos , Degeneraciones Espinocerebelosas/diagnóstico , Expansión de Repetición de Trinucleótido/genética , Ataxina-7 , Ataxinas , Estudios de Casos y Controles , Fluorescencia , Tamización de Portadores Genéticos , Pruebas Genéticas , Humanos , Proteínas del Tejido Nervioso/metabolismo , Degeneraciones Espinocerebelosas/genéticaRESUMEN
We describe a four-generation Italian family with a novel form of juvenile-onset, slowly progressive, autosomal dominant cerebellar ataxia. Eleven affected family members have been evaluated. The mean age at onset was 19.5 years with no evidence of anticipation. The first symptoms were invariably unbalanced standing and mild gait incoordination. Gaze-evoked nystagmus was prominent at onset, while patients with longer disease duration developed slow saccades, ophthalmoparesis and, often, ptosis. Deep tendon reflexes in lower limbs were increased in 80% of the cases. Genetic analysis excluded the presence of pathological repeat expansions in spinocerebellar ataxia (SCA) types 1-3, 6-8, 10, 12 and 17, and DRPLA genes. Linkage exclusion tests showed no evidence of association with other known SCA loci. A genome-wide screen analysis identified linkage with chromosome 18 markers. A maximum two-point limit of determination score of 4.20 was found for marker D18S53. Haplotype analysis refined a critical region of 7.9 Mb between markers D18S1418 and D18S1104. This new SCA locus on 18p11.22-q11.2 has been designated SCA28. Candidate genes within the critical interval are currently screened for mutations.
Asunto(s)
Cromosomas Humanos Par 18 , Genes Dominantes , Ataxias Espinocerebelosas/genética , Adulto , Encéfalo/patología , Mapeo Cromosómico , Análisis Mutacional de ADN , Femenino , Ligamiento Genético , Marcadores Genéticos , Haplotipos , Humanos , Italia , Escala de Lod , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Mutación , Linaje , Fenotipo , Ataxias Espinocerebelosas/patologíaRESUMEN
Several diagnostic strategies have been applied to the detection of FMR1 gene repeat expansions in fragile X syndrome. Here, we report a novel polymerase chain reaction-based strategy using the Expand Long Template PCR System (Roche Diagnostics, Mannheim, Germany) and the osmolyte betaine. Repeat expansions up to approximately 330 CGGs in males and up to at least approximately 160 CGGs in carrier women could be easily visualized on ethidium bromide agarose gels. We also demonstrated that fluorescence analysis of polymerase chain reaction products was a reliable tool to verify the presence of premutation and full mutation alleles both in males and in females. This technique, primarily designed to detect premutation alleles, can be used as a routine first screen for expanded FMR1 alleles.
Asunto(s)
Alelos , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/genética , Mutación/genética , Reacción en Cadena de la Polimerasa/métodos , Betaína , Análisis Mutacional de ADN , Femenino , Colorantes Fluorescentes , Humanos , Masculino , Expansión de Repetición de TrinucleótidoAsunto(s)
Síndrome de Camurati-Engelmann/complicaciones , Accidente Cerebrovascular/complicaciones , Insuficiencia Vertebrobasilar/complicaciones , Adulto , Angiografía Cerebral , Humanos , Imagen por Resonancia Magnética , Masculino , Accidente Cerebrovascular/patología , Insuficiencia Vertebrobasilar/patologíaRESUMEN
BACKGROUND: Autosomal dominant cerebellar ataxias are a clinical and genetically heterogeneous group of progressive neurodegenerative diseases, at present associated with 22 loci (spinocerebellar ataxia [SCA] 1-SCA8, SCA10-SCA19, SCA21, SCA22, fibroblast growth factor 14 [FGF14]-SCA, and dentatorubral-pallidoluysian atrophy [DRPLA]). The relevant gene has been identified in 12 cases (SCA1-3, SCA6-8, SCA10, SCA12, FGF14, and DRPLA), and in all but the recently identified SCA14, SCA17, PRKCG and FGF14 genes, the defect consists of the expansion of a short nucleotide repeat. OBJECTIVES: To investigate the relative prevalence of SCA1-3, SCA6-8, SCA10, SCA12, and SCA17 gene expansions in Italian families with hereditary ataxia, specifically to verify the occurrence of SCA10, SCA12, and SCA17 in Italy; and to analyze samples from probands with negative test results at the initial screening by means of the repeat expansion detection technique to identify CAG/CTG expansions in novel loci.Patients Two hundred twenty-five unrelated Italian index cases with hereditary ataxia, most (n = 183) of whom presented with a clear dominantly transmitted trait. RESULTS: We found that SCA1 and SCA2 gene mutations accounted for most cases (21% and 24%, respectively). We found SCA3, SCA6, SCA7, SCA8, and SCA17 to be very rare (approximately 1% each), and no case of SCA10 or SCA12 was identified. Half of the index cases (113/225) were negative for expansions in the known SCA genes. Repeat expansion detection analysis performed on 111 of these cases showed a CAG/CTG repeat expansion of at least 50 triplets in 22 (20%). Twenty-one of 22 expansions could be attributed to length variation at 2 polymorphic loci (expanded repeat domain CAG/CTG 1 [ERDA1] or CTG repeat on chromosome 18q21.1 [CTG18.1]). In 1 patient, the expansion was assigned to the DRPLA gene. CONCLUSIONS: The distribution of SCA1-3 and SCA6-7 gene mutations is peculiar in Italy. We found a relatively high frequency of SCA1 and SCA2 gene expansions; SCA3, SCA6, and SCA7 mutations were rare, compared with other European countries. No SCA10 or SCA12 and only a few SCA8 (2/225) and SCA17 (2/225) families were detected. In patients negative for defects in known SCA genes, repeat expansion detection data strongly suggest that, at least in our population, CAG/CTG expansions in novel genes should be considered an unlikely cause of the SCA phenotype.
Asunto(s)
Ataxias Espinocerebelosas/genética , Expansión de Repetición de Trinucleótido , Adulto , Anciano , Ataxina-1 , Ataxina-3 , Ataxina-7 , Ataxinas , Canales de Calcio/genética , Análisis Mutacional de ADN , Femenino , Humanos , Italia , Masculino , Repeticiones de Microsatélite , Persona de Mediana Edad , Biología Molecular , Proteínas del Tejido Nervioso/genética , Proteínas Nucleares/genética , Linaje , Reacción en Cadena de la Polimerasa , Proteínas/genética , ARN Largo no Codificante , ARN no Traducido , Proteínas RepresorasRESUMEN
At least 18 human genetic diseases are caused by expansion of short tandem repeats. Here we describe a successful application of a fluorescent PCR method for the detection of expanded repeats in FRDA1, SCA10, and SCA12 genes. Although this test cannot give a precise estimate of the size of the expansion, it is robust, reliable, and inexpensive, and can be used to screen large series of patients. It proved useful for confirming the presence of large expansions in the Friedreich ataxia gene following an ambiguous result of long-range PCR, as well as rapid pre-screening for large repeat expansions associated with Friedreich ataxia and SCA10 and the shorter repeat expansions associated with SCA12.
Asunto(s)
Ataxia de Friedreich/genética , Proteínas de Unión a Hierro/genética , Ataxias Espinocerebelosas/genética , Expansión de Repetición de Trinucleótido/genética , Estudios de Casos y Controles , Fluorescencia , Ataxia de Friedreich/patología , Humanos , Reacción en Cadena de la Polimerasa , Ataxias Espinocerebelosas/patología , FrataxinaRESUMEN
Mutations in the ATM gene are responsible for the autosomal recessive syndrome Ataxia Telangiectasia (AT). In a group of 26 classical AT Italian patients studied by protein truncation test (PTT), we identified six new mutations, never reported so far. Mutations -spread over the entire ATM coding sequence with not clear "hot-spot"- are four frameshifts (2192_2193insA, 3110delC, 7150delA, 8368delA), one splice site alteration (8850G>T, causing exon 63 skipping) and one nonsense change (6913C>T, Q2305X). The identification of ATM gene mutations is important for understanding the molecular basis of the disease, and is essential for diagnosis and genetic counseling.