RESUMEN
Genomic imprinting, the differential expression of paternal and maternal alleles, involves many chromosomal regions and plays a role in development and growth. Differential methylation of maternal and paternal alleles is a hallmark of imprinted genes, and thus methylation assays are widely used to support the identification of novel imprinted genes. Either blood or lymphoblast DNAs are most often used in these assays, even though methylation levels may change in cell culture. We undertook a systematic survey of parent-of-origin-specific methylation of chromosome 7 genes and ESTs by comparing DNA samples from cases of maternal and paternal uniparental disomy for chromosome 7 using DNA from fresh blood and lymphoblast cell lines. Our results revealed that up to 41% of genes and ESTs show parent-of-origin-specific methylation differences in lymphoblast DNA after only a short time in culture, whereas methylation differences were not seen in blood DNA. The methylation changes occurred most commonly on paternal chromosome 7, whereas alterations on maternal chromosome 7 were more infrequent and weaker. These findings indicate that methylation patterns may change significantly during cell culture in a parent-of-origin-dependent manner and suggest that methylation is maintained differently on maternal and paternal chromosomes 7.
Asunto(s)
Cromosomas Humanos Par 7/química , Cromosomas Humanos Par 7/genética , Metilación de ADN , Impresión Genómica/genética , Linfocitos/metabolismo , Adolescente , Adulto , Alelos , Southern Blotting , Línea Celular , Preescolar , Mapeo Cromosómico , ADN/sangre , Etiquetas de Secuencia Expresada , Femenino , Regulación de la Expresión Génica , Humanos , Linfocitos/citología , Masculino , Modelos Genéticos , Polimorfismo Genético , Caracteres SexualesAsunto(s)
Aberraciones Cromosómicas , Cromosomas Humanos Par 7/genética , Trastornos del Crecimiento/genética , Adulto , Niño , Preescolar , ADN/genética , Repeticiones de Dinucleótido/genética , Salud de la Familia , Femenino , Genotipo , Trastornos del Crecimiento/patología , Humanos , Lactante , Masculino , Fenotipo , SíndromeRESUMEN
Maternal uniparental disomy of chromosome 7 (matUPD7), the inheritance of both chromosomes from only the mother, is observed in approximately 10% of patients with Silver-Russell syndrome (SRS). It has been suggested that at least one imprinted gene that regulates growth and development resides on human chromosome 7. To date, three imprinted genes-PEG1/MEST, gamma2-COP, and GRB10-have been identified on chromosome 7, but their role in the etiology of SRS remains uncertain. In a systematic screening with microsatellite markers, for matUPD7 cases among patients with SRS, we identified a patient who had a small segment of matUPD7 and biparental inheritance of the remainder of chromosome 7. Such a pattern may be explained by somatic recombination in the zygote. The matUPD7 segment at 7q31-qter extends for 35 Mb and includes the imprinted gene cluster of PEG1/MEST and gamma2-COP at 7q32. GRB10 at 7p11.2-p12 is located within a region of biparental inheritance. Although partial UPD has previously been reported for chromosomes 6, 11, 14, and 15, this is the first report of a patient with SRS who has segmental matUPD7. Our findings delimit a candidate imprinted region sufficient to cause SRS.
Asunto(s)
Anomalías Múltiples/genética , Aneuploidia , Cromosomas Humanos Par 7/genética , Impresión Genómica/genética , Trastornos del Crecimiento/genética , Anomalías Múltiples/fisiopatología , Proteínas Portadoras/genética , Mapeo Cromosómico , Proteína Coatómero , Intercambio Genético/genética , Padre , Femenino , Trastornos del Crecimiento/fisiopatología , Humanos , Lactante , Masculino , Repeticiones de Microsatélite/genética , Madres , Proteínas/genética , SíndromeRESUMEN
An inherited defect in intestinal anion exchange, congenital chloride diarrhea (CLD), was recently shown to be caused by mutations in the down-regulated in adenoma (DRA) gene. A three base pair deletion resulting in the loss of an amino acid valine (V317del) in the predicted CLD/DRA protein was shown to be responsible for all CLD cases in a Finnish founder population. Two additional mutations, H124L and 344delT, were found in Polish CLD patients. Here, we screened for additional mutations in a set of 14 CLD families of Polish, Swedish, North American, and Finnish origin using primers that allowed mutation searches directly from genomic DNA samples. We found eight novel mutations in the CLD/DRA gene. The mutations included two transversions, one transition, one insertion, and four small deletions. Of 11 sequence alterations detected so far, nine lie clustered in three short segments that are 49 bp, 39 bp, and 65 bp in size, respectively. These short segments span only 6.7% of the total cDNA length, suggesting functional importance or mutation-prone DNA regions of the corresponding CLD/DRA protein domains.