1/12. Prenatal evaluation of a de novo X;9 translocation.A case of X-autosome translocation was diagnosed prenatally [46,X, t(X;9)(p21.3 approximately 22.1;q22]. We describe the use of fluorescence in situ hybridization (FISH) to estimate the integrity of the Duchenne muscular dystrophy (DMD) gene. X-inactivation studies were used as well to assess the probability of phenotypic abnormalities associated with functional partial disomy X and monosomy 9.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
2/12. Mental retardation and early onset of weakness in a girl with a dystrophinopathy and a large Xp21-23 deletion.A 2-year-old girl presented with severe global developmental delay weakness, and an elevated serum creatine kinase level. Her muscle biopsy was consistent with an active dystrophy with absence of dystrophin in about half of the muscle fibers. Fluorescent in situ hybridization analysis showed her karyotype to be 46, X, delX p23.1-p21.1. This large deletion includes the dystrophin gene as well as the region involved in X-linked mental retardation. The genetic mechanism for the manifestation of both diseases is likely non-random inactivation of the x chromosome. To our knowledge, the combination of this dystrophinopathy in association with severe mental retardation has not been described in a girl.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
3/12. Somatic mosaicism for a deletion of the dystrophin gene in a carrier of Becker muscular dystrophy.Duchenne muscular dystrophy (DMD) and the allelic milder form of Becker muscular dystrophy (BMD) are caused by mutations of the dystrophin gene on the short arm of the x chromosome. One third of affected individuals are expected to result from de novo mutations. Genetic counselling of families with sporadic cases is complicated by the potential meiotic origin of the mutation in the mother resulting in germline mosaicism. Here we present direct evidence for combined somatic and germline mosaicism for a deletion of the dystrophin gene, thereby proving the mitotic origin of this deletion and pinpointing a further potential pitfall for genetic counselling. The mother of a BMD son and a BMD carrier daughter, both carrying a deletion of dystrophin cDNA 7 (0.5 kb Hind III fragment) and cDNA 8, was herself clinically healthy and had normal creatine kinase levels. A muscle specimen of the mother showed mild overall pathology as well as focal dystrophin deficiency. In contrast chromosomal in situ suppression (CISS) hybridization of metaphase chromosomes using a cosmid clone of the corresponding cDNA deleted in her son revealed no evidence of somatic mosaicism in their lymphocytes. These results emphasize the value of an approach correlating genetic and immunological data for the definition of a carrier state in BMD or DMD. The possibility of somatic mosaicism should be considered when genetic counselling of a family with a sporadic case of BMD or DMD is performed.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
4/12. PGD for dystrophin gene deletions using fluorescence in situ hybridization.Duchenne muscular dystrophy and Becker muscular dystrophy (DMD and BMD) are caused by mutations in the dystrophin gene (Xp21). In two-thirds of DMD/BMD cases, the mutation is a large deletion of one or several exons. We have established PGD for DMD/BMD using interphase fluorescence in situ hybridization (FISH) analysis on single nuclei from blastomeres for the detection of deletions of specific exons in the dystrophin gene. We performed PGD for two carrier females; one had a deletion of exons 45-50 (DMD), and the other had a deletion of exons 45-48 (BMD). An exon 45-specific probe was used in combination with probes for the X and Y centromeres. Using this straightforward approach, we can distinguish affected and unaffected male embryos as well as carrier female and normal female embryos. Three cycles were performed for each patient, which resulted in a pregnancy and the birth of a healthy girl. To the best of our knowledge, this approach for PGD has not been previously reported. The use of interphase FISH is an attractive alternative to sexing or PCR-based mutation detection for PGD patients with known deletions of the dystrophin gene.- - - - - - - - - - ranking = 5keywords = hybridization (Clic here for more details about this article) |
5/12. Possibilities and limitations of carrier diagnosis in families with Duchenne muscular dystrophy caused by deletions in the major hot spot region using pulsed-field gel electrophoresis.The cDNA probes cf56a, b identify deletions in 45% of the investigated patients with Duchenne and Becker muscular dystrophy (DMD/BMD). But carrier detection by junction fragments using normal gel electrophoresis conditions separating fragments up to a size of about 25 kilobases is possible only in selected cases. We, therefore, applied separation of Sfi I-digested dna by rotating-field gel electrophoresis (RFE) in combination with Southern blot transfer and hybridization using cf56a for this purpose. In this study we compared hybridizing fragments of dna from three DMD families with different deletion patterns: distal to the Sfi I-site F located between exon 48/49 (family A), proximal to the Sfi I-site F including the P20 intron (family B), and bridging the Sfi I-site F (family C). Junction fragments in the dna of 2 affected boys and their mothers were detected in families B and C. Carrier determination on this basis was performed for family C. Given these three families are representative for other families with similar deletions, it will be possible to offer carrier diagnosis using RFE in 38% of the studied families with DMD/BMD caused by deletions in the major hot spot region.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
6/12. De novo dna microdeletion in a girl with turner syndrome and Duchenne muscular dystrophy.The single x chromosome of a girl with turner syndrome (45,X) and typical Duchenne muscular dystrophy was investigated at the chromosomal and dna levels. No visible abnormality of the residual x chromosome was found upon high-resolution R-banding. The dna was analysed by Southern blotting and hybridization with seven cloned probes mapping in the Xp21 region where the Duchenne locus is thought to be located. A molecular deletion was detected with probes pERT 87.1, pERT 87.8, and pERT 87.15. The other probes (754, C7, 99.6, and RC8) gave a normal signal. The dna alleles seen in the two parents indicated that the deletion found in the propositus had occurred de novo on a maternal x chromosome.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
7/12. Familial deletion in Becker type muscular dystrophy within the pXJ region.A family of an isolated patient with Becker muscular dystrophy has been investigated by dna analysis. Southern blotting and hybridization were performed with six probes (C7, pERT87.15, pERT87.1, pXJ1.1, pXJ2.3, 754) mapping in the Xp21 region. A deletion within the pXJ region was demonstrated in the proband, his mother and all three sisters. The segregation pattern for the restriction fragment length polymorphisms (RFLPs) observed with the pXJ probes as well as with pERT87.15, pERT87.1 and 754 probes indicates that the deletion is of grandpaternal origin.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
8/12. Additional case of female monozygotic twins discordant for the clinical manifestations of Duchenne muscular dystrophy due to opposite X-chromosome inactivation.A pair of female monozygotic (MZ) twins, heterozygous carriers for a deletion in the DMD gene and discordant for the clinical manifestations of Duchenne muscular dystrophy, were analyzed by molecular studies, in situ hybridization, and methylation pattern of X chromosomes to search for opposite X inactivation as an explanation of their clinical discordance. Results in lymphocytes and skin fibroblast cell lines suggest a partial mirror inactivation with the normal x chromosome preferentially active in the unaffected twin, and the maternal deleted x chromosome preferentially active in the affected twin. A review shows that MZ female twins discordant for X-linked diseases are not uncommon. Twinning and X inactivation may be interrelated and could explain the female twins discordant for X-linked traits.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
9/12. Skewed inactivation of an x chromosome deleted at the dystrophin gene in an asymptomatic mother and her affected daughter.A girl with severe Becker muscular dystrophy and apparently normal chromosomes had a heterozygous deletion for exons 51, 52, and 53 of the dystrophin gene. This deletion was transmitted by her mother, who was unaffected. To differentiate the normal and the deleted X chromosomes, fluorescence in situ hybridization (FISH) was applied to metaphase chromosomes, using probes for both exons 51 and 52, which are only 388 and 113 base pairs long, respectively. FISH signals were observed in one or both chromatids of one chromosome, but never on both chromosomes, suggesting the lack of hybridization on the deleted x chromosome. Using 5-bromodeoxyuridine incorporation to differentiate the late (inactive) and the early replicating (active) X chromosomes, 77% of the signals were observed on the active X chromosomes in the mother. This percentage was only 18% in the daughter, suggesting that skewed inactivation of the X chromosomes was responsible for the phenotypic differences.- - - - - - - - - - ranking = 2keywords = hybridization (Clic here for more details about this article) |
10/12. in situ hybridization shows direct evidence of skewed X inactivation in one of monozygotic twin females manifesting Duchenne muscular dystrophy.A novel combination of conventional and molecular cytogenetic techniques was used to investigate the expression of an X-linked recessive disorder in one of monozygotic (MZ) twin females. These twins carry a deletion, approximately 300 kb in length, in one of their X chromosomes within the dystrophin gene, which is responsible for Duchenne muscular dystrophy (DMD) in one twin [Richards et al.: Am J Hum Genet 46:672-681, 1990]. A unique dna fragment generated from an exon within this gene deletion was hybridized in situ to both twins' metaphase chromosomes, a probe which would presumably hybridize only to the normal x chromosome and not to the x chromosome carrying the gene deletion. chromosomes were identified by reverse-banding (R-banding) and by the addition of 5-bromodeoxyuridine (BrdU) in culture to distinguish early and late replicating X chromosomes, corresponding to active and inactive X chromosomes, respectively. Hybridization experiments showed predominant inactivation of the normal x chromosome in the twin with DMD. This is the first report showing direct evidence at the chromosome level of unequal inactivation of cytogenetically normal X chromosomes resulting in the manifestation of an X-linked recessive disorder in one of monozygotic twin females. This study may now facilitate other research of unequal X inactivation and of females manifesting X-linked recessive disorders.- - - - - - - - - - ranking = 4keywords = hybridization (Clic here for more details about this article) |
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