1/180. Increased sister chromatid exchange in bone marrow and blood cells from Bloom's syndrome.Bone-marrow cells from a patient with Bloom's syndrome cultured for 48 h in the presence of BudR exhibited a striking increase in the number of sister chromatid exchanges (SCEs) in comparison to that in the marrow cells of a patient with treated polycythemia vera (PV). Thus, it appears that an increased incidence of SCE in Bloom's syndrome occurs in various differentiated types of cells, not just blood lymphocytes, and constitutes the syndrome's most characteristic cytogenetic feature. In contrast, the incidence of SCE was not increased in marrow cells and lymphocytes of the particular PV patient studied here, whose cells did exhibit increased numbers of chromatid and chromosome gaps and breaks, presumably as result of the patient's earlier treatment. An increased frequency of SCE was demonstrated in Bloom's syndrome lymphocytes using both a technique based on BudR incorporation and one based on labeling with tritated deoxycytidine. This observation constitutes evidence against the increase of SCE being due to an unusual reaction to BudR. By conventional cytogenetic techniques, chromosome instability, including chromatid and chromosome breaks, but no homologous chromatid interchanges were also recognized in Bloom's syndrome bone-marrow cells incubated in vitro (without BudR) for either 1.k or 16 h. This observation points to the existence of chromosome instability in vivo.- - - - - - - - - - ranking = 1keywords = instability (Clic here for more details about this article) |
2/180. Familial cerebellar hypoplasia and pancytopenia without chromosomal breakages.Two siblings manifested a neuro-haematologic syndrome characterised by low birth weight, failure to thrive, chronic persistent tongue ulceration, severe truncal ataxia and pancytopenia without either telangiectasia or chromosomal instability. One sibling died from sepsis and the cerebellum demonstrated reduced cellularity of the molecular and granular layers with relative preservation of purkinje cells and minimal gliosis. A surviving sibling has shown haematologic progression to a myelodysplastic disorder. There was no evidence of any chromosomal instability following exposure of fibroblasts and lymphocytes to irradiation. monosomy-7 was not present in the surviving sibling. We suspect that these two patients represent another example of the rare Hoyeraal-Hreidarsson syndrome and we are currently engaged in very close monitoring of the surviving sibling for evidence of any karyotypic abnormality.- - - - - - - - - - ranking = 1keywords = instability (Clic here for more details about this article) |
3/180. Chromosome instability in lymphocytes from two patients affected by three sequential primary cancers: the role of fragile sites.The chromosomal aberration rate and the expression of fragile sites induced by aphidicolin were evaluated in metaphase chromosomes obtained from peripheral blood lymphocytes of two untreated patients with multiple primary cancers. Spontaneous aberrations of chromosome number and structure and chromosome fragility were compared with controls with the use of the same methods. Chromosomal aberration rates and expression frequencies of fragile sites were significantly higher in the patients than in normal control subjects. In the patients, all but one structural chromosome aberration involved at least one fragile site. Our results suggest that fragile sites may be unstable regions of the human genome, which might play an important role in the genetic instability associated with cancer predisposition.- - - - - - - - - - ranking = 2.5keywords = instability (Clic here for more details about this article) |
4/180. Screening for submicroscopic chromosome rearrangements in children with idiopathic mental retardation using microsatellite markers for the chromosome telomeres.Recently much attention has been given to the detection of submicroscopic chromosome rearrangements in patients with idiopathic mental retardation. We have screened 27 subjects with mental retardation and dysmorphic features for such rearrangements using a genetic marker panel screening. The screening was a pilot project using markers from the subtelomeric regions of all 41 chromosome arms. The markers were informative for monosomy in both parents at 3661902 loci (40.6%, 95% confidence interval 37.0-44.2%) in the 22 families where dna was available from both parents. In two of the 27 subjects, submicroscopic chromosomal aberrations were detected. The first patient had a 5-6 Mb deletion of chromosome 18q and the second patient had a 4 Mb deletion of chromosome 1p. The identification of two deletions in 27 cases gave an aberration frequency of 7.5% without adjustment for marker informativeness (95% confidence interval 1-24%) and an estimated frequency of 18% if marker informativeness for monosomy was taken into account. This frequency is higher than previous estimates of the number of subtelomeric chromosome abnormalities in children with idiopathic mental retardation (5-10%) although the confidence interval is overlapping. Our study suggests that in spite of the low informativeness of this pilot screening, submicroscopic chromosome aberrations may be a common cause of dysmorphic features and mental retardation.- - - - - - - - - - ranking = 10.184453520007keywords = microsatellite (Clic here for more details about this article) |
5/180. Maternal uniparental isodisomy for chromosome 14 detected prenatally.Maternal uniparental disomy (UPD) for chromosome 14 (upd(14)mat) has been associated with a distinct phenotype. We describe the first case of maternal uniparental isodisomy for chromosome 14 detected prenatally, in a pregnancy with mosaicism for trisomy 14 observed in both a chorionic villus sample (CVS) and in amniocytes. Detailed analysis of polymorphic microsatellites showed that the fetus was essentially isodisomic for one of the mother's chromosomes 14 and that recombination had introduced a mid-long arm region of heterodisomy. The fetus, which died in utero at 18 weeks, showed no apparent pathological features. The case demonstrates for the first time a maternal meiosis II non-disjunction of chromosome 14 leading to a trisomic conception which has been incompletely corrected by 'rescue' in the early embryo.- - - - - - - - - - ranking = 2.5461133800017keywords = microsatellite (Clic here for more details about this article) |
6/180. Duplication within chromosome region 15q11-q13 in a patient with similarities to prader-willi syndrome confirmed by region-specific and band-specific fish.We report on a patient presenting with mental retardation and obesity and a proximal duplication of chromosome 15. The patient shared some clinical signs with prader-willi syndrome. With a region-specific paint, generated by microdissection, a duplication in region 15q11.2-q13 was shown to be present. Subsequently, FISH with probes localized to chromosome region 15q11.2-q12 and microsatellite analysis was used to characterize this chromosome aberration further and an insertion duplication within the region frequently deleted in Prader-Willi and angelman syndrome was demonstrated.- - - - - - - - - - ranking = 2.5461133800017keywords = microsatellite (Clic here for more details about this article) |
7/180. Maternal UPD 20 in a hyperactive child with severe growth retardation.Maternal uniparental disomy was observed in a 4-year-old boy with severe pre- and postnatal growth retardation (body height: 85 cm = 12 cm < third percentile, head circumference: 48 cm = 10 cm < third percentile), a few minor facial findings, and with apparent hyperactivity. His intelligence is within the normal range for his age. karyotype analysis revealed two cell lines, one apparently normal with 46,XY, the other with a tiny marker (47,XY, mar). microdissection and reverse chromosome painting using the marker dna library as a probe, as well as PCR analysis revealed that the marker is from chromosome 20 and contains only the centromere and pericentromeric segments, but none of the pericentromeric loci for microsatellites. Microsatellite analysis of 25 chromosome 20 loci disclosed maternal uniparental disomy for all 16 informative markers. Maternal heterodisomy was evident for seven loci of the short arm segment 20p11.2-pter. Maternal isodisomy was found at five loci, three of them map to the proximal 20p11.2 segment and two to 20q. To our knowledge, this is the first case of maternal disomy 20 in humans.- - - - - - - - - - ranking = 2.5461133800017keywords = microsatellite (Clic here for more details about this article) |
8/180. angelman syndrome with uniparental disomy due to paternal meiosis II nondisjunction.We report a case of angelman syndrome (AS) with paternal uniparental disomy (pUPD) of chromosome 15. This 6-year-old girl with overgrowth had frequent, but only provoked laughter, was mildly ataxic with limb hypertonia, and had no intelligible speech. She had deep-set eyes, protruding tongue, and prominent chin. The karyotype was normal. dna analysis with microsatellites from chromosome 15 showed no inheritance of maternal alleles both within and outside the AS critical region. Proximal markers showed reduction to homozygosity of paternal alleles, intermediate markers showed nonreduction, and distal markers reduction, thus suggesting a meiosis II nondisjunction event in the father with two crossovers. This is, to our knowledge, the first reported case of AS due to meiosis II nondisjunction. We present detailed physical measurements in this patient, adding to the clinical description of the milder phenotype in AS due to pUPD.- - - - - - - - - - ranking = 2.5461133800017keywords = microsatellite (Clic here for more details about this article) |
9/180. chediak-higashi syndrome associated with maternal uniparental isodisomy of chromosome 1.chediak-higashi syndrome (CHS) is a rare autosomal recessive disorder (incidence around 1 in 106 births), characterised by a complex immunologic defects, reduced pigmentation, and presence of giant granules in many different cell types. It most likely results from defective organellar trafficking or protein sorting. The causative gene (LYST) has recently been identified and shown to be homologous to the beige locus in the mouse. CHS has always been reported associated with premature-termination-codon mutations in both alleles of LYST. We report a unique patient with CHS, who was homozygous for a stop codon in the LYST gene on chromosome 1 and who had a normal 46,XY karyotype. The mother was found to be a carrier of the mutation, whereas the father had two normal LYST alleles. Non-paternity was excluded by the analysis of microsatellite markers from different chromosomes. The results of 13 informative microsatellite markers spanning the entire chromosome 1 revealed that the proband had a maternal isodisomy of chromosome 1 encompassing the LYST mutation. The proband's clinical presentation also confirms the absence of imprinted genes on chromosome 1.- - - - - - - - - - ranking = 5.0922267600035keywords = microsatellite (Clic here for more details about this article) |
10/180. Digynic triploid infant surviving for 46 days.We report on a triploid infant who survived for 46 days. She had severe intrauterine growth retardation, relative macrocephaly, and a small, noncystic placenta, which are manifestations compatible with type II phenotype. Cultured amniotic fluid cells, skin fibroblasts, cord blood, and peripheral blood lymphocytes all showed a nonmosaic 69,XXX karyotype. Analysis of chromosomal heteromorphisms and microsatellite dna polymorphisms in the infant and her parents indicated that the extra haploid set in the infant resulted from nondisjunction at maternal second meiosis. Postzygotic, mitotic nondisjunction was ruled out because of the presence of both homozygous and heterozygous markers of maternal origin. A search of the literature demonstrated five triploid infants, including the girl we described, who survived 4 weeks or more, and the parental origin of whose triploidy was studied: four were digynic and one was diandric. These findings support the notion that type II triploids are digynic in parental origin and that they survive longer than type I, diandric triploids.- - - - - - - - - - ranking = 2.5461133800017keywords = microsatellite (Clic here for more details about this article) |
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