1/64. 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 = chromosome (Clic here for more details about this article) |
2/64. Exclusion of chromosome 9 helps to identify mild variants of acromesomelic dysplasia Maroteaux type.Acromesomelic dysplasia Maroteaux type (AMDM) is an autosomal recessive disorder belonging to the group of acromesomelic dysplasias. AMDM is characterised by severe dwarfism with shortening of the middle and distal segments of the limbs. An AMDM gene has recently been mapped to human chromosome 9p13-q12 by homozygosity mapping in four consanguineous families. Here, we show linkage of the disease gene to chromosome 9p13-q12 in four of five consanguineous AMDM families and its exclusion in a fifth family with two children affected with a mild form of the disease. This study suggests that genetic heterogeneity accounts for the variable clinical and radiological severity of AMDM.- - - - - - - - - - ranking = 1.5keywords = chromosome (Clic here for more details about this article) |
3/64. Exclusion of chromosome 15q21.1 in autosomal-recessive weill-marchesani syndrome in an inbred Lebanese family.We report an inbred family where 3 siblings had short stature, brachydactyly, limitation of joint movements, microspherophakia, luxated lenses, glaucoma, and heart malformations. parents of the affected siblings were relatively short, but did not have any of the other features present in their siblings. Those clinical features are consistent with the Weill Marchesani syndrome (MIM 277600). Both autosomal-recessive and autosomal-dominant pedigrees have been reported, with a possible linkage to chromosome 15q21.1 in the latter. Linkage analysis at 15q21.1 in this Lebanese family allowed us to exclude the role of this region in the etiology of the syndrome. Speculations regarding the pathogenesis of the disorder are discussed.- - - - - - - - - - ranking = 1.25keywords = chromosome (Clic here for more details about this article) |
4/64. Isochromosome consisting of terminal short arm and proximal long arm X in a girl with short stature.A 16-year-old girl with short stature, short neck, shield chest, and cubitus valgus was studied. FISH analyses of her structurally altered X chromosome showed a der(X)- (wcpX ,TelXp/Yp ,SHOX ,STS ,KAL-, 37A12-,DXZ1 ,XIST ,97L7 ,300O13-,404F- 18-,417G15-,404F18-,140A-,TelXq/Yq-). These results, together with the high-resolution banding analysis, indicated her karyotype to be 46,X,der(X)(Xpter-->Xp22.3::Xq22.3--> cen-->Xq22.3::Xp22.3-->Xpter). The der(X) was an isochromosome, consisting of duplicated terminal short arms and duplicated proximal long arms. This in turn suggested that the chromosome was formed through pericentric inversion of an X chromosome, followed by isochromosome formation through sister chromatid exchange at Xp, close to the centromere. Replication R-banding analysis showed that the abnormal X chromosome was late replicating. Analysis of digestion patterns with a methylation-sensitive restriction endonuclease of the phosphoglycerate kinase 1 gene, located in Xq13.3, indicated that its inactivation patterns were completely skewed.- - - - - - - - - - ranking = 2.5keywords = chromosome (Clic here for more details about this article) |
5/64. Brachytelephalangic dwarfism due to the loss of ARSE and SHOX genes resulting from an X;Y translocation.Here we report an 8-year-old male patient who had mesomelic shortening of forearms and legs, brachytelephalangia and ichthyotic skin lesions. Chromosomal analysis showed an X;Y translocation involving the short arm of the X chromosome (Xp). fluorescence in situ hybridization (FISH) and molecular studies localized the breakpoints on Xp22.3 in the immediate vicinity of the KAL gene demonstrating deletions of steroid sulfatase (STS), arylsulfatase E (ARSE), and short stature homeo box (SHOX) genes. It was suspected that the patient was suffering from chondrodysplasia punctata because of a loss of the arylsulfatase E (ARSE) gene. However, no stippled epiphyses were to be seen in the neonatal radiograph. Interestingly, this patient is the first case with a proven loss of the ARSE gene without chondrodysplasia punctata, assuming that chondrodysplasia punctata is not an obligatory sign of ARSE gene loss. Brachytelephalangia was the only result of ARSE gene deletion in this case. The patient's mother also had dwarfism and showed Madelung deformity of the forearms. She was detected as a carrier of the same aberrant X chromosome. The male patient did not show Madelung deformity, demonstrating that Lerri-Weill syndrome phenotype may be still incomplete in children with SHOX gene deletion. The wide clinical spectrum in the male and the Leri-Weill phenotype in his mother are the results of both a deletion involving several sulfatase genes in Xp22.3 and the SHOX gene located in the pseudoautosomal region. Nevertheless, there is no explanation for the absence of chondrodysplasia punctata despite the total loss of the ARSE gene. Further studies are necessary to investigate genotype/phenotype correlation in cases with translocations or microdeletions on Xp22.3, including the ARSE and the SHOX gene loci.- - - - - - - - - - ranking = 0.5keywords = chromosome (Clic here for more details about this article) |
6/64. Hallermann-Streiff syndrome and progeria.Reported is an atypical, severe case of Hallermann-Streiff syndrome combined with progeria, bilateral microphthalmus, cataracts, and normal chromosome count. A plea is made for study into the teratology of abnormal chemical, metabolic, and other forces that attack the early stages of the development of the human fetus and produce multiple anomalies.- - - - - - - - - - ranking = 0.25keywords = chromosome (Clic here for more details about this article) |
7/64. Craniofacial anomalies, deafness, brachydactyly, short stature, and moderate mental retardation due to a cryptic 6p;11q translocation.Monozygotic twin brothers are described who share clinical features which include: moderate mental retardation, short stature, macrocephaly, frontal bossing, ptosis, low-set ears, brachydactyly, 5th fingers clinodactyly, single palmar creases, cryptorchidism, and prelingual sensorineural deafness. One of the twins presented with mild cardiac dilatation and died at age 3(1/2) from cardiac arrest during an episode of acute respiratory infection. While chromosome analyses performed for both twins on peripheral blood showed apparently normal karyotypes, screening for all telomeric regions on the surviving propositus revealed a combination of partial 6p trisomy and partial 11q monosomy. A balanced reciprocal translocation was found in the father. The phenotype of the twins is most likely related to this cryptic chromosomal rearrangement. The fact that the phenotype in this family partially overlaps with some previously reported phenotypes is discussed.- - - - - - - - - - ranking = 0.25keywords = chromosome (Clic here for more details about this article) |
8/64. Lack of expression of XIST from a small ring X chromosome containing the XIST locus in a girl with short stature, facial dysmorphism and developmental delay.A 46,X,r(X) karyotype was found in a three and a half year old girl with short stature, facial dysmorphism and developmental delay. The clinical findings were consistent with the phenotype described in a limited number of patients with small ring X chromosomes lacking the XIST locus, a critical player in the process of x chromosome inactivation. Surprisingly, in our patient, fluorescent in situ hybridisation demonstrated that the XIST locus was present on the ring X. However, expression studies showed that there was no XIST transcript in peripheral blood cells, suggesting that the ring X had not been inactivated. This was confirmed by the demonstration that both of the patient's alleles for the androgen receptor gene were unmethylated, and that both of the patient's ZXDA alleles were expressed. The active nature of the ring X would presumably result in overexpression of genes that may account for the developmental delay observed for the patient. Using polymorphic markers along the X chromosome, the ring X was determined to be of paternal origin with one breakpoint in the long arm between DXS8037 and XIST and one in the short arm in Xp11.2 between DXS1126 and DXS991. To attempt to determine why the XIST gene failed to be expressed, the promoter region was sequenced and found to have a base change at the same location as a variant previously associated with nonrandom x chromosome inactivation. This mutation was not seen in over one hundred normal X chromosomes examined; however, it was observed in the paternal grandmother who did not show substantial skewing of x chromosome inactivation.- - - - - - - - - - ranking = 2.5keywords = chromosome (Clic here for more details about this article) |
9/64. Maternal isodisomy for 14q21-q24 in a man with diabetes mellitus.We report a 20-year-old man with maternal uniparental disomy for chromosome 14 (UPD14) and maturity-onset diabetes mellitus (DM). He had pre- and postnatal growth retardation, developed DM at age 20 years without any autoimmune antibodies, and had a mosaic 45,XY,der(14;14)(q10;q10)[129]/46,XY, 14,der(14;14)(q10;q10)[1] karyotype. Allelotyping using microsatellite markers covering the entire 14q indicated segmental maternal isodisomy for 14q21-q24 and maternal heterodisomy of the remaining regions of the chromosome. It is thus tempting to speculate that the segmental isodisomy led to reduction to homozygosity for a mutant gene and thus caused his DM, although the possibility of coincidental occurrence of the two events cannot totally be ruled out. fluorescence in situ hybridization (FISH) analysis using BAC clone probes revealed that the isodisomic segment did not overlap any known IDDM or NIDDM susceptibility loci on chromosome 14, suggesting a novel locus for a subset of DM at the isodisomic segment.- - - - - - - - - - ranking = 0.75keywords = chromosome (Clic here for more details about this article) |
10/64. Hallermann-Streiff syndrome associated with small cerebellum, endocrinopathy and increased chromosomal breakage.Hallermann-Streiff syndrome (HSS) is a rare clinic entity of unknown aetiology. Further clinical and metabolic-genetic evaluations are indicated. A 2-mo-old female baby presented with ocular abnormalities and severe failure to thrive since birth. The clinical features were compatible with the diagnosis of HSS. Further imaging, metabolic and cytogenetic examinations were performed. Features characteristic of HSS were dyscephaly with mandibular and nasal cartilage hypoplasia, microphthalmia, bilateral cataracts with congenital glaucoma, natal teeth and proportionate dwarfism. Rare anomalies such as choanal atresia and small cerebellum, very low insulin-like growth factor i level, hypothyroidism, generalized organic aciduria were also noticed. An increased chromosomal breakage rate is suggestive of the existence of some dna repair defects in HSS patients. CONCLUSION: The associated anomalies in this patient may broaden the clinical spectrum of HSS. Underlying conditions of organic aciduria, growth factor deficiency and impaired dna repair are likely to contribute to the progeria-like facies, congenital cataracts and growth failure.- - - - - - - - - - ranking = 1.7814624069754keywords = breakage (Clic here for more details about this article) |
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