RESUMO
Mutations in the FBN1 gene are the major cause of Marfan syndrome (MFS), an autosomal dominant connective tissue disorder, which displays variable manifestations in the cardiovascular, ocular, and skeletal systems. Current molecular genetic testing of FBN1 may miss mutations in the promoter region or in other noncoding sequences as well as partial or complete gene deletions and duplications. In this study, we tested for copy number variations by successively applying multiplex ligation-dependent probe amplification (MLPA) and the Affymetrix Human Mapping 500 K Array Set, which contains probes for approximately 500,000 single-nucleotide polymorphisms (SNPs) across the genome. By analyzing genomic DNA of 101 unrelated individuals with MFS or related phenotypes in whom standard genetic testing detected no mutation, we identified FBN1 deletions in two patients with MFS. Our high-resolution approach narrowed down the deletion breakpoints. Subsequent sequencing of the junctional fragments revealed the deletion sizes of 26,887 and 302,580 bp, respectively. Surprisingly, both deletions affect the putative regulatory and promoter region of the FBN1 gene, strongly indicating that they abolish transcription of the deleted allele. This expectation of complete loss of function of one allele, i.e. true haploinsufficiency, was confirmed by transcript analyses. Our findings not only emphasize the importance of screening for large genomic rearrangements in comprehensive genetic testing of FBN1 but, importantly, also extend the molecular etiology of MFS by providing hitherto unreported evidence that true haploinsufficiency is sufficient to cause MFS.
Assuntos
Deleção de Genes , Perda de Heterozigosidade , Síndrome de Marfan/genética , Proteínas dos Microfilamentos/genética , Sequência de Bases , Quebra Cromossômica , Estudos de Coortes , Análise Mutacional de DNA/métodos , Fibrilina-1 , Fibrilinas , Testes Genéticos , Haplótipos , Humanos , Dados de Sequência Molecular , Polimorfismo de Nucleotídeo Único , RNA Mensageiro/análiseRESUMO
Aortic dilatation/dissection (AD) can occur spontaneously or in association with genetic syndromes, such as Marfan syndrome (MFS; caused by FBN1 mutations), MFS type 2 and Loeys-Dietz syndrome (associated with TGFBR1/TGFBR2 mutations), and Ehlers-Danlos syndrome (EDS) vascular type (caused by COL3A1 mutations). Although mutations in FBN1 and TGFBR1/TGFBR2 account for the majority of AD cases referred to us for molecular genetic testing, we have obtained negative results for these genes in a large cohort of AD patients, suggesting the involvement of additional genes or acquired factors. In this study we assessed the effect of COL3A1 deletions/duplications in this cohort. Multiplex ligation-dependent probe amplification (MLPA) analysis of 100 unrelated patients identified one hemizygous deletion of the entire COL3A1 gene. Subsequent microarray analyses and sequencing of breakpoints revealed the deletion size of 3,408,306 bp at 2q32.1q32.3. This deletion affects not only COL3A1 but also 21 other known genes (GULP1, DIRC1, COL5A2, WDR75, SLC40A1, ASNSD1, ANKAR, OSGEPL1, ORMDL1, LOC100129592, PMS1, MSTN, C2orf88, HIBCH, INPP1, MFSD6, TMEM194B, NAB1, GLS, STAT1, and STAT4), mutations in three of which (COL5A2, SLC40A1, and MSTN) have also been associated with an autosomal dominant disorder (EDS classical type, hemochromatosis type 4, and muscle hypertrophy). Physical and laboratory examinations revealed that true haploinsufficiency of COL3A1, COL5A2, and MSTN, but not that of SLC40A1, leads to a clinical phenotype. Our data not only emphasize the impact/role of COL3A1 in AD patients but also extend the molecular etiology of several disorders by providing hitherto unreported evidence for true haploinsufficiency of the underlying gene.
Assuntos
Doenças da Aorta/genética , Colágeno Tipo III/genética , Colágeno Tipo V/genética , Haploinsuficiência/genética , Hemizigoto , Miostatina/genética , Deleção de Sequência/genética , Doenças da Aorta/patologia , Pareamento de Bases/genética , Sequência de Bases , Quebra Cromossômica , Colágeno Tipo III/ultraestrutura , Colágeno Tipo V/ultraestrutura , Sondas de DNA/metabolismo , Feminino , Humanos , Masculino , Dados de Sequência Molecular , Linhagem , Fenótipo , Reação em Cadeia da PolimeraseRESUMO
Se trata de lograr una predicción epidemiológica de la enfermedad meningocócica tomando como unidad de tiempo la semana, con el propósito de obtener un período largo de análisis. Se combina lo probabilístico de Reed-Frost con un modelo dinámico, donde las relaciones matemáticas básicas entre las clases epidemiológicas se expresan por un sistema de ecuaciones en diferencias finitas y los coeficientes de transferencia entre las clases son fijos. Se divide la población, en este modelo, en 7 clases epidemiológicas: susceptibles, portadores, incubandos, enfermos, recuperados, fallecidos e inmunes. Se ha considerado el proceso de simulación para toda la población y para una estratificación en 2 grupos de edades: menores de 15 años y de 15 años y más. Se implantó el modelo construido en BASIC para la microcomputadora NEC-9801, este programa tiene carácter interactivo y se obtienen representaciones gráficas de las curvas epidemiológicas de la enfermedad meningocócica