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Correlación genotipo-fenotipo y análisis molecular en pacientes con síndrome Down
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Contreras Bravo, Nora Constanza
Silva Aldana, Claudia Tamar
Mateus Arbelaez, Heidi Eliana
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2012-12-29
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Universidad del Rosario
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Resumen
El síndrome Down (SD) es la trisomía más común en humanos, presentándose en 1 de cada 745 nacidos vivos y es la causa más frecuente de retardo mental. El origen más observado de la trisomíaes una no disyunción meiótica (95%), la cual generalmente es de origen materno, mientras un 5% se debe a errores post-cigóticos mitóticos. Objetivo: identificar el origen parental delcromosoma 21 extra, el momento del error no disyuncional y establecer una correlación entre estos eventos y las manifestaciones fenotípicas de los pacientes afectados. Materiales y métodos: se estudiaron cincuenta familias con un hijo con SD mediante el uso de cinco short tandem repeats (STR) a lo largo de 21q, se construyeron los haplotipos de cada paciente y sus padres, determinandoel origen parental y el momento en que surgió el error no disyuncional. Resultados:en 80% de las familias el error fue en meiosis I y 20% en la meiosis II; 98% de los cromosomasadicionales fue de origen materno y 2% paterno. Se encontró correlación genotipo-fenotipo en ocho características estudiadas: cuello corto y ancho, tercera fontanela, labio inferior prominente, paladar estrecho y corto, raíz del hélix cruzando la concha, alopecia, pliegue único palmar yotras anomalías como nevus y xeroderma y eventos de recombinación en 24,5% de las familias analizadas. Conclusiones: la edad materna y la variación en el número de recombinaciones está asociada con no disyunciones meióticas I y II; se encontró correlación entre el momento del errorno disyuncional y algunas variables clínicas.
Abstract
O síndrome de Down (SD) é a trissomia mais comum em humanos, apresentando-se em 1 de cada745 nascidos vivos e é a causa mais frequentes de retardo mental. A origem mais observada datrissomia é uma não-disjunção meiótica (95%), a qual geralmente é de origem materna, enquantoum 5% se deve a erros pós-zigoticos mitóticos. Objetivo: identificar a origem parental do cromossoma 21 extra, o momento do erro não-disjuncional e estabelecer uma correlação entre esteseventos e as manifestações fenotípicas dos pacientes afetados. Materiais e métodos: se estudaram cinquenta famílias com um filho com SD mediante o uso de cinco short tandem repeats (STR) aolonge de 21q, se construíram os haplótipos de cada paciente e seus pais, determinando a origemparental e o momento em que surgiu o erro não-disjuncional. Resultados: em 80% das famíliaso erro foi em meiose I e 20% na meiose II; 98% dos cromossomas adicionais foi de origem maternoe 2% paterno. Encontrou-se correlação genótipo-fenótipo em oito características estudadas:pescoço curto e amplo, terceira fontanela, lábio inferior proeminente, paladar apertado e curto,raiz da hélix a través da concha, alopecia, prega palmar única e outras anomalias como nevus exeroderma e eventos de recombinação em 24,5% das famílias analisadas. Conclusões:a idade maternae a variação no número de recombinações está associada com não-disjunções meióticas I e II; encontrou-se correlação entre o momento do erro não disjuncional e algumas variáveis clínicas.
Down Syndrome (DS) is the most common trisomy in human beings. Its incidence is estimatedin one of 745 live births. On a global scale, it is the most frequent cause of mental retardation.The origin of this trisomy is due to a meiotic non-disjunction in about 95% of cases and is usuallymaternal, especially in women above 35 years of age. The remaining 5% is due to errors inpost-zygotic mitosis. Objective: identify the parental origin of the extra chromosome 21, whenthe error is not disyuncional and establish a correlation between these events and phenotypic manifestations of the patients affected. Materials and methods: we studied fifty families with achild with DS, using 5 STRs markers along 21q which allowed identification of the origin of chromosome 21 additional parents, the time when the error occurred and recombination presents. Thestatistical analysis was done using the package SPSS version 15.0 for Windows. Results: in 80% of households in the error was meiosis I and 20% in meiosis II, 98% of the additional chromosomes was home maternal and paternal 2% similar to those reported by other authors, correlation was found genotype-phenotype characteristics studied at 8, neck short and wide, third fontanel, prominent lower lip, palate narrow and short, crossing hélix root of the shell, alopecia, singlepalm crease and other anomalies as nevi and xeroderma and recombination events in 24,5% ofthe families tested. Conclusions: the maternal age and variation in the number of recombinationis not associated with disjunctions meiotics I and II genotype phenotype correlation was found, but the sample size should be expanded in order to establish with certainty that the correlations.
Down Syndrome (DS) is the most common trisomy in human beings. Its incidence is estimatedin one of 745 live births. On a global scale, it is the most frequent cause of mental retardation.The origin of this trisomy is due to a meiotic non-disjunction in about 95% of cases and is usuallymaternal, especially in women above 35 years of age. The remaining 5% is due to errors inpost-zygotic mitosis. Objective: identify the parental origin of the extra chromosome 21, whenthe error is not disyuncional and establish a correlation between these events and phenotypic manifestations of the patients affected. Materials and methods: we studied fifty families with achild with DS, using 5 STRs markers along 21q which allowed identification of the origin of chromosome 21 additional parents, the time when the error occurred and recombination presents. Thestatistical analysis was done using the package SPSS version 15.0 for Windows. Results: in 80% of households in the error was meiosis I and 20% in meiosis II, 98% of the additional chromosomes was home maternal and paternal 2% similar to those reported by other authors, correlation was found genotype-phenotype characteristics studied at 8, neck short and wide, third fontanel, prominent lower lip, palate narrow and short, crossing hélix root of the shell, alopecia, singlepalm crease and other anomalies as nevi and xeroderma and recombination events in 24,5% ofthe families tested. Conclusions: the maternal age and variation in the number of recombinationis not associated with disjunctions meiotics I and II genotype phenotype correlation was found, but the sample size should be expanded in order to establish with certainty that the correlations.
Palabras clave
Síndrome Down , Trisomía , Recombinación , No disyunción genética , PCR.
Keywords
Trissomia , Recombinação , Não-disyunção genética , Síndrome de Down , PCR , Trisomy , Down syndrome , Recombination , Nondisjunction genetic
