RESUMEN
Pitt-Hopkins syndrome (PTHS), characterized by severe intellectual disability and typical facial gestalt, is part of the clinical spectrum of Rett-like syndromes. TCF4, encoding a basic helix-loop-helix (bHLH) transcription factor, was identified as the disease-causing gene with de novo molecular defects. While PTHS appears to be a recognizable clinical entity, it seems to remain underdiagnosed, especially when facial gestalt is less typical. With the aim to facilitate the diagnosis of PTHS and to increase its rate and specificity, we have investigated 33 novel patients and defined a Clinical Diagnosis Score. Analysis of 112 individuals (79 previously reported and 33 novel patients) allowed us to delineate the TCF4 mutational spectrum, with 40% point mutations, 30% small deletions/insertions, and 30% deletions. Most of these were private mutations and generated premature stop codons. Missense mutations were localized in the bHLH domain, which is a mutational hotspot. No obvious difference was observed between patients harboring truncating, missense mutations, or deletions, further supporting TCF4 haploinsufficiency as the molecular mechanism underlying PTHS. In this study, we have summarized the current knowledge of TCF4 molecular pathology, reported all the mutations in the TCF4 database (http://www.LOVD.nl/TCF4), and present a novel and comprehensive diagnostic strategy for PTHS.
Asunto(s)
Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/genética , Cromosomas Humanos Par 18/genética , Hiperventilación/diagnóstico , Discapacidad Intelectual/diagnóstico , Factores de Transcripción/genética , Adolescente , Niño , Preescolar , Cromosomas Humanos Par 18/química , Bases de Datos Genéticas , Facies , Femenino , Estudios de Asociación Genética , Variación Genética , Genotipo , Haploinsuficiencia , Haplotipos , Humanos , Hiperventilación/genética , Lactante , Discapacidad Intelectual/genética , Masculino , Mutación Missense , Fenotipo , Estructura Terciaria de Proteína , Eliminación de Secuencia , Inversión de Secuencia , Índice de Severidad de la Enfermedad , Factor de Transcripción 4RESUMEN
Pitt-Hopkins syndrome (PHS) is a probably underdiagnosed, syndromic mental retardation disorder, marked by hyperventilation episodes and characteristic dysmorphism (large beaked nose, wide mouth, fleshy lips, and clubbed fingertips). PHS was shown to be caused by de novo heterozygous mutations of the TCF4 gene, located in 18q21. We selected for this study 30 unrelated patients whose phenotype overlapped PHS but which had been initially addressed for Angelman, Mowat-Wilson, or Rett syndromes. In 10 patients we identified nine novel mutations (four large cryptic deletions, including one in mosaic, and five small deletions), and a recurrent one. So far, a total of 20 different TCF4 gene mutations have been reported, most of which either consist in deletion of significant portions of the TCF4 coding sequence, or generate premature stop codons. No obvious departure was observed between the patients harboring point mutations and large deletions at the 18q21 locus, further supporting TCF4 haploinsufficiency as the molecular mechanism underling PHS. In this report, we also further specify the phenotypic spectrum of PHS, enlarged to behavior, with aim to increase the rate and specificity of PHS diagnosis.
Asunto(s)
Anomalías Múltiples/genética , Discapacidad Intelectual/genética , Mutación , Eliminación de Secuencia , Factores de Transcripción TCF/genética , Adolescente , Niño , Preescolar , Cromosomas Humanos Par 18 , Codón de Terminación , Hibridación Genómica Comparativa , Análisis Mutacional de ADN , Discapacidades del Desarrollo/genética , Femenino , Humanos , Hiperventilación/genética , Cariotipificación , Masculino , Fenotipo , Síndrome , Proteína 2 Similar al Factor de Transcripción 7RESUMEN
OBJECTIVE: Evaluation of the use of short probes as a detection system in real-time PCR. DESIGN AND METHOD: Comparison of results obtained with hybridization probes with and without locked nucleic acid (LNA) residues in the detection of fetal DNA in maternal serum. RESULTS: The use of chimeric LNA/DNA probes led to a slight but significantly higher level of sensitivity as well as a higher level of fluorescence signal. CONCLUSION: Chimeric LNA/DNA probes offer an interesting alternative detection method in real-time PCR.
Asunto(s)
Sondas de ADN/química , Proteínas de Unión al ADN/genética , Proteínas Nucleares/genética , Oligonucleótidos Antisentido/química , Plasma/metabolismo , Reacción en Cadena de la Polimerasa/métodos , Factores de Transcripción/genética , Cromosomas Humanos Y , Sondas de ADN/genética , Femenino , Humanos , Masculino , Hibridación de Ácido Nucleico , Oligonucleótidos , Oligonucleótidos Antisentido/genética , Embarazo , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Procesos de Determinación del Sexo , Proteína de la Región Y Determinante del SexoRESUMEN
OBJECTIVE: The purpose of this study was to determine the accuracy of the none-invasive prenatal determination of polymerase chain reaction (PCR)-based fetal RhD genotyping. STUDY DESIGN: A prospective case series was undertaken on all RhD-negative pregnant women presenting for genetic counseling in our prenatal diagnosis center from January 2001 until December 2002. Results were compared with serologic RhD typing of the newborns. RESULTS: Among the 285 pregnant women who participated in the study, fetal RhD status could be determined for 283 patients. In 2 cases, the RhD-negative phenotype of the mother was not the result of a complete RHD gene deletion, and therefore, the status of the fetus could not be determined. Neither false-negative nor false-positive results were observed. CONCLUSION: The present report demonstrates that a reliable fetal RHD genotype determination can be achieved with 100% accuracy. It is therefore possible to consider that such an assay could be systematically proposed to all RhD-negative pregnant women in order to more effectively utilize RhD prophylaxis.