Showing papers on "Ring chromosome published in 1991"

An infant with deletion of the distal long arm of chromosome 15 (q26.1----qter) and loss of insulin-like growth factor 1 receptor gene.

Abstract: We report on an infant with a previously undescribed chromosome 15 deletion (q26.1----qter) and compare the clinical findings with those of 7 reported patients with deletions of distal 15q, as well as ring chromosome 15 syndrome patients. Most of the patients with deletions of distal 15q, including our patient, have intrauterine growth retardation (IUGR), microcephaly, abnormal face and ears, micrognathia, highly arched palate, renal abnormalities, lung hypoplasia, failure to thrive, and developmental delay/mental retardation. Several genes have been assigned to the 15q25----qter region, including insulin-like growth factor 1 receptor (IGF1R). DNA analysis from our patient documented the loss of one IGF1R gene copy. Our study further localizes the IGF1R gene distal to the 15q26.1 band. It is interesting to speculate that the severe IUGR and postnatal growth deficiency of our patient and other patients with similar chromosome 15 deletions are related to the loss of an IGF1R gene copy which may lead to an abnormal number and/or structure of the receptors.

Chromosomal origin of small ring marker chromosomes in man: characterization by molecular genetics.

Abstract: Ten cases of small ring chromosomes which did not stain with distamycinA/DAPI and did not possess satellite regions associated with nucleolus-organizing regions are described In situ hybridization with a battery of biotinylated pericentric repeat probes specific either for individual chromosomes or for groups of chromosomes allowed the identification of the chromosomal origin of these marker chromosomes There was one example of a marker derived from each of chromosomes 1, 3, 6, 14, 16, 18, 20, 13 or 21, and the X, and there were two examples of markers derived from chromosome 12 One case possessed two markers, one derived from chromosome 6, and one derived from the X The mechanism of generation of ring marker chromosomes is discussed Five of seven cases who could be phenotypically assessed were abnormal Three of these--the first with a ring chromosome derived from chromosome 1; the second with two markers, one derived from chromosome 6 and the other from the X chromosome; and the third with a ring chromosome derived from chromosome 20--each possessed distinctive facies Additional cases with identified rings may allow the delineation of new chromosomal syndromes

The relationship between colony-forming ability, chromosome aberrations and incidence of micronuclei in V79 Chinese hamster cells exposed to microwave radiation.

Abstract: Cultured V79 Chinese hamster fibroblast cells were exposed to continuous radiation, frequency 7.7 GHz, power density 0.5 mW/cm2 for 15, 30 and 60 min. The effect of microwave radiation on cell survival and on the incidence and frequency of micronuclei and structural chromosome aberrations was investigated. The decrease in the number of irradiated V79 cell colonies was related to the power density applied and to the time of exposure. In comparison with the control samples there was a significantly higher frequency of specific chromosome aberrations such as dicentric and ring chromosomes in irradiated cells. The presence of micronuclei in irradiated cells confirmed the changes that had occurred in chromosome structure. These results suggest that microwave radiation can induce damage in the structure of chromosomal DNA.

Inherited ring chromosomes: an analysis of published cases.

Abstract: A review of case reports on patients with ring chromosome revealed 30 individuals (plus two fetuses) who inherited the ring from a total of 23 carrier parents (21 mothers and 2 fathers). The proportion of cases with inherited rings, among all patients with a ring, was calculated to be 5.6% as an upper limit. However, because of a propable difference in survival and fertility between individuals with transmitted and de novo rings, and because of the preferential publication of cases involving inherited rings (and thus a publication bias), the proportion of inherited rings should in reality be no more than 1%. Out of 30 transmitted rings, there were 9 where parent and child were both mosaics, suggesting an inherited instability of the chromosome involved leading to de novo re-formation of the ring in the second generation. The relatively mild clinical manifestations of ring chromosomes, in general, was found to be even more striking in familial cases. In half of the offspring the phenotype was very similar to that of the parent. However, in about a third of cases the offspring were more severely (mentally) affected. This fact should be considered in genetic counseling of clinically normal women who carry a ring chromosome.

Partial deletion of chromosome 6p: delineation of the syndrome.

Abstract: Here we summarize the clinical findings of five new patients and nine patients reported in the literature with deletions of the short arm of chromosome 6. The del(6p) syndrome appears to include the following clinical findings: mental retardation, microcephaly, abnormal sutures, broad nasal bridge, various eye and ear abnormalities, a short neck with excess skin folds, and a normal birth weight and length.

Ring chromosome 14 syndrome. Report of two cases, including extended evaluation of a previously reported patient and review.

Abstract: A case of r(14) chromosome is described and new information is added to a previously reported patient. The r(14) syndrome is reviewed on the basis of 37 known patients. The major features include prenatal and postnatal growth retardation, mental retardation, seizures, microcephaly, and distinct facial dysmorphism, including elongated face, narrow palpebral fissures, epicanthus, and broad nasal bridge. Other characteristic anomalies found only in some patients are retinal anomalies, lymphoedema of hands and feet, and prones to pulmonary infections.

Ring Y chromosome: molecular characterization by DNA probes.

Abstract: A young male with a karyotype of 46, X,+mar is described. Physical mapping of the marker chromosome by using Y-specific single-copy or moderately repeated DNA sequences as molecular probes showed that

An investigation of ring and dicentric chromosomes found in three Turner's syndrome patients using DNA analysis and in situ hybridisation with X and Y chromosome specific probes.

Abstract: We have studied three patients with features of Turner's syndrome, two with a 45,X/46,X,r(?) and the third with a 45,X/46,X,dic?(Y) karyotype. Because Turner's syndrome patients with a mosaic karyotype containing a Y chromosome are known to have a high risk of developing gonadal tumours, we used DNA analysis and in situ hybridisation with X and Y specific probes to identify the chromosomal origin of the rings and dicentric chromosomes in the three index patients. Both ring chromosomes were shown to be of X origin, while the dicentric was composed of Y chromosome material. We discuss the importance of using a combination of molecular and cytogenetic analyses in such cases.

Flecked retina associated with ring 17 chromosome.

Abstract: We report the case of a mentally retarded male with a ring 17 chromosome who had subretinal drusen-like deposits in each eye. This is the second report of flecked retina in a patient with ring 17 chromosome, suggesting that there may be a causal relationship between abnormalities of chromosome 17 and retinal pigment epithelial or photoreceptor dysfunction.

Severe anomalies associated with ring chromosome 7.

Abstract: A newborn infant with the polyasplenia sequence, intrauterine growth retardation, cutaneous nevi, and minor anomalies was found to have mosaicism for ring chromosome 7. This patient's anomalies are markedly different from those of previous patients reported with this cytogenetic anomaly.

Interstitial deletion of chromosome 9q with coexistence of the deleted segment as a ring chromosome. A case report.

Abstract: In a mentally retarded female an interstitial deletion of a chromosome 9 and an additional ring chromosome was shown, which by positive hybridisation with a no 9 library was considered to be the excised segment. The functional centromere and C and DA/DAPI positive material as well on the ring chromosome are explained by a break within the centromere close to the constitutive heterochromatin and supports the hypothesis of "latent" centromere(s).

Ring chromosome 15 and 15qs+ mosaic: clinical and cytogenetic behaviour spanning 29 years.

Abstract: A phenotypic female with mild mental retardation, minor facial anomalies, and short stature has been evaluated clinically and cytogenetically over 29 years. At age 59, she remains physically well and shows no signs of dementia. Cytogenetic analysis, performed on peripheral blood specimens on 10 occasions between 1961 and 1990, showed mosaicism with one cell line containing a large stable ring (15) chromosome and another cell line without the ring but with a 15qs +. The different cell lines remained constant. The case provides information on the natural history of the ring chromosome 15 syndrome.

Two forms of ring 13 in a child with rhabdomyosarcoma.

Abstract: Mosaicism for two forms of ring 13 was found in a child with embryonal rhabdomyo-sarcoma of the bladder, minor anomalies, and developmental delay. Her chromosome constitution was 46, XX, r(13)(p11q34)/46, XX, r del(13)(p11q14). Both cell lines were present in lymphocytes and fibroblasts. The cell line with the smaller ring chromosome predominated in both tissues. The child's manifestations reflect the presence of both cell lines.

Cytogenetic and molecular characterization of a small ring chromosome in the complex karyotype of a girl with Turner syndrome.

Abstract: Blood samples of an 8-year-old girl with Turner syndrome were examined using cytogenetic and molecular methods. Chromosomal analyses revealed a mosaic karyotype consisting of 25% 47,X,der(X),+r(X) and 75% 46,X,der(X) cells. Southern blot hybridizations with Y-specific DNA probes excluded a Y chromosomal origin of the small ring chromosome. In situ hybridization using DNA probe pXBR showed it to be X-derived. Examination of C-, Q-, and R-banding patterns indicated that the der(X) chromosome probably arose by a translocation event.

Cornelia de Lange syndrome with ring chromosome 3.

Abstract: The report of Lakshminarayana and Nallasivam' concerning a patient with ring chromosome 3 and Cornelia de Lange syndrome recalls an earlier controversy. We had followed the cue of Falek et al2 in suggesting a relationship between chromosome 3 and the syndrome of Brachmann and de Lange.3 Francke and Opitz' emphasised the superficiality of this resemblance, and personal experience with five cases of dup(3q) syndrome3 5 has documented several differences between the two malformation patterns. As with dup(3q) patients, the photograph published by Lakshminarayana and Nallasivam' resembles the gestalt of Cornelia de Lange syndrome but has atypical manifestations. Absent are the grim facies and micromelia, while the presence of a dilated cisterna magna, as pointed out by the authors, is unusual. Their case is also very different from our ring 3 patient6 and it is unfortunate that the location and variability of the breakpoints were not specified. ' Begging for examination now is the parental origin of 3q regions in 3q partial trisomy/monosomy and Cornelia de Lange syndrome. Could the quantity and imprinting7 of unbalanced material explain their similarities and differences?

De novo ring chromosome 3: a new case with a mild phenotype.

Abstract: We report an 18 year old female with a de novo ring chromosome 3 found after investigation for short stature. Her karyotype was interpreted as 46,XX, r(3)(p26.2q29). Her phenotype is milder than previously reported cases and illustrates the mild end of the spectrum of the ring chromosome 3 phenotype.

Ring chromosome 9 in a newborn male presenting with facial dysmorphia, hypospadias and skeletal abnormalities.

Abstract: A newborn male presenting with a peculiar appearance, hypertonia, a flexum attitude, hypospadias and skeletal abnormalities was found to bear a r 9 chromosome. A phenotypic distinction between early and late presenting forms is discussed.

Ring chromosome 3 in a mentally retarded adult dwarf

Abstract: A 46-year-old man with mental retardation, growth failure and some dysmorphic features is found to have a 46,XX,r(3)(p26q29) karyotype in 93% of his peripheral lymphocytes. This observation is compared with previously cases of ring 3. The existence of a "ring syndrome" is considered.

Ring chromosome 22: a case report.

Abstract: A three year old girl with ring chromosome 22 is described. The clinical findings include epicanthus, flat nasal bridge, hypertelorism, long eye-lashes, lymphoedema, hypoplastic toe nails, hydrocephalus and muscular hypotonia. Speech and language development is delayed. At three years the child begins to walk.

Constitutional extra chromosomal element in a family with Wilms' tumor.

Abstract: We report the presence of an extra chromosomal element in a family with Wilms' tumor (WT). This family has three children, two of whom were affected. One son, the proband, had bilateral and one daughter had unilateral WT. The first child, the father, and the mother did not have WT. The son with bilateral WT had a ring chromosome (R) both in the lymphocytes as well as in the kidney tissue. The size of the ring varied considerably from cell to cell. The daughter with unilateral WT had an abnormal clone containing a small chromosomal ring (r) in phytohemagglutinin (PHA)-stimulated and Epstein-Barr virus (EBV)-transformed lymphocytes. The mother had a karyotype similar to that of the daughter with WT. We hypothesize that the proband's ring chromosome could be the amplified form of the r inherited from the mother. Chromosome 11 was cytogenetically normal in all the cells examined of the affected children and the unaffected mother. In situ hybridization with a centromere-specific DNA cocktail indicated dispersed centromeric DNA both in r and R.

Ring chromosome 8 associated with microcephaly.

Abstract: A two-year-old mental defective girl with microcephaly and minor dysmorphic features had a 46,XX,r(8) karyotype. Low birth weight, short stature, and mental retardation were common features in the four known patients with r(8).

[A report of 2 cases of Turner's syndrome with a ring X chromosome].

Abstract: The authors report two cases of Turner syndrome with clinical evidence of only primitive hypogonadism and short stature. Karyotype analysis showed X ring mosaicism which is present only in 5% of cases of Turner syndrome. The authors agree with the hypothesis suggesting no relationship between break points on the X chromosome and phenotypical aspect. An earlier diagnosis is auspicious so that, using correct therapy, final height should be improved.

Isolation ofa HumanDNA Sequence WhichSpanstheFragile X

Abstract: Summary Toidentify the sequencesinvolved intheexpression ofthefragile X andtocharacterize themolecular basis ofthegenetic lesion, we haveconstructed yeastartificial chromosomes (YACs) containing humanDNA and havescreened themwithcloned DNA probes which map close tothefragile site atXq27.3. We haveisolated andpartly characterized a YACcontaining approximately 270kbofhumanDNA froman X chromosome which expressesthefragile X.This sequenceina yeastartificial ring chromosome, XTY26,hybridizes tothe twoclosest DNA markers, VK16andDo33,which flank thefragile site. ThehumanDNA sequencein XTY26also spansthefragile site on chromosome insitu hybridization. Whena restriction map ofXTY26, derived byusing infrequently cutting restriction enzymes, iscompared withsimilar YAC maps derived from non-fragile-X patients, no large-scale differences areobserved. ThisYAC,XTY26,may enable (a)thefragile site tobefully characterized atthemolecular level and(b)thepathogenetic basis ofthefragile-X syndrome tobedetermined.

Parental Origin and Mechanism of Formation of de novo Chromosome Abnormalities : 25 Cases of Numerical and Structural Abnormalities Determined by Restriction Fragment Length Polymorphisms

Abstract: Parental origin and mechanism of formation of de novo numerical and structural chromosome abnormalities were studied in 25 cases using RFLPs as genetic markers. In 8 of the 10 (5 autosomal and 5 X-chromosomal) numerical abnormalities studied, the origin and the mechanism of formation were ascertained. Of five 21-trisomics, two resulted from a maternal second meiotic nondisjunction, one (a 46/47,+21 mosaic) from mitotic nondisjunction of a paternally-derived chromosome 21, and the remaining two were uninformative. The origin and the mechanism of formation of the additional X chromosomes in the five patients with poly-X chromosomes (a case of XXXXX and four of XXXXY) studied were identical. They all arose through three nondisjunctions at maternal meiosis: once at the first meiosis and simultaneously twice at the second meiosis. These observations indicate that the parental origin of numerical abnormalities is not different between autosomes and X chromosome, the maternal origin being predominant. Of the 15 structural abnormalities studied, the origin was ascertained in 11. An interstitial deletion of chromosome 15 [del(15)(q11.1q12)] in 2 of 5 cases arose at paternal meiosis. A 15q15q translocation in one of 2 cases resulted from centric misdivision of a maternal chromosome 15 followed by duplication of its long-arm, and thus the translocated chromosome is in the condition of "maternal uniparental disomy". A case of partial monosomy 21 (monosomy for 21pter-q21.3) resulted from a translocation between paternal chromosomes 2 and 21. The origin of X-chromosomal structural abnormalities in 3 cases were paternal and that in the other 4 cases maternal. Partial X-chromosome duplication [dup(Xp)] in one patient arose through an unequal sister chromatid exchange in the paternal X chromosome, partial deletion [del(Xp)] in one arose at the paternal meiosis, isochromosome X [i(Xq)] in three resulted from centric fission followed by duplication of Xq in a maternal X chromosome, isodicentric chromosome X [inv dup(Xq)] in one arose through an unequal exchange between sister chromatids in a maternal. X chromosome, and ring chromosome X [r(X)] in the other case arose at maternal meiosis. These results on the structural abnormalities suggest that the de novo abnormalities due to events involving centromere disruption arise predominantly during oogenesis, while those due to simple breakage-reunion events occur preferentially during spermatogenesis.