Late-replicating ring X-chromosomes identified by r-banding after BrdU pulse

Summary A detailed chromosome analysis was carried out in 3 patients presenting the mosaicism, 45,XO/46,Xr(X). In 2 patients, the r(X) chromosome was found to be latereplicating using R-banding techniques after a BrdU pulse administered 6 h before harvesting the leukocyte culture. The clinical symptomatology presents the great variability already observed in association with this karyotype. Only a short stature was common to the 3 patients. Case 1 is a 6-year-old girl with moderate mental retardation; case 2 is a 16-year-old girl with primary amenorrhea and absence of secondary sexual characteristics; case 3 is a 24-year-old woman whose puberty and normal sexual development occurred at age 17.     

Cytogenetic investigation of patients with primary amenorrhea

Primary amenorrhea refers to absence of spontaneous menarche even after the age of 16. Cytogenetic analysis in two cases with primary amenorrhea, short stature, poorly developed secondary sexual characteristics, and growth retardation were studied. Routine GTG-band analysis of metaphases from peripheral blood leucocytes revealed female karyotype with a 15(ps+) and an isochromosome of X, i(Xq), in one patient and 46,X, i(Xq), in another patient. Ascertainment of the karyotype aided in confirmation of the provisional diagnosis, a better phenotype-genotype correlation to understand clinical heterogeneity in genetic counseling.     

Identification of Y-chromosomal DNA in a Turner syndrome mosaic by polymerase chain reaction.

A 15.5-year-old female was referred for primary amenorrhea and slow development of secondary sex characteristics. The karyotype revealed 45,X/46,X,+mar (75%/25%). The small marker chromosome was C-band and Q-band negative. It appeared to be primarily centromeric with some light G-band staining material on either side. Females with Y-chromosomal material are at an increased risk for gonadal neoplasia and this patient was studied further to investigate the possibility that the marker was a deleted Y chromosome. Polymerase chain reaction (PCR) analysis of this patient's DNA revealed the presence of Y-chromosomal material presumably derived from the marker chromosome. These results indicate that the PCR technique, in conjunction with cytogenetic analysis, can identify possible Y-chromosomal material. This testing provides critical information necessary for correct medical followup of Turner syndrome mosaic patients.     

Short arm deletion of an X chromosome, 46,XXp-

Summary A 27-year-old patient of short stature with primary amenorrhea and other slight Turner signs showed a 46,XX,del(X) (qterp11:) karyotype, identified by a combination of fluorescence and giemsa-banding technique. By BUdR incorporation the deleted X chromosome was shown to be the late replicating one.     

X-X translocation in a patient with gonadal dysgenesis and the problem of phenotype-karyotype correlations

Summary A sex-chromatin-positive woman without stunted growth, but with primary amenorrhea, and some stigmas of pure gonadal dysgenesis had the chromosome constitution 45,X/46,Xt(X;X)(q27;q27). The abnormal chromosome formed a large Barr body and was late-labeling. The chromosome consisted of two X chromosomes attached by their long arms (end-to-end), both apparently having the partial distal deletion. Both centromeric regions showed C-staining but only one constriction. The chromosome is interpreted as an isodicentric with only one centromere functioning. Some problems of phenotype-karyotype correlations are discussed.     

A complex mosaicism 45,X/46,X,del(Xq)/46,X,idic(Xq) in a patient with secondary amenorrhea

A complex mosaicism involving the X chromosome was found in a 35-year-old female affected by secondary amenorrhea and short stature. Her karyotype was: 45,X[20]/46,X,del(X)(pter-->q26::qter)[15]/46,X,idic(X)(pter-->q26::q26-->pter)[9]. No cell contained both abnormal X chromosomes. This observation would suggest a possible mechanism underlying the formation of isodicentric chromosomes.     

Chromosomal abnormalities and hormonal disorders of primary amenorrhea patients in Egypt

BACKGROUND:

Primary amenorrhea is defined as the absence of menstruation and secondary sexual characteristics in phenotypic women aged 14 years or older. Hormonal disorders are main causes of primary amenorrhea. Common hormonal cause of primary amenorrhea includes pituitary dysfunction and absent ovarian function. The aim of this study was to estimate the incidence and types of chromosomal abnormalities in patients with primary amenorrhea in Egypt.

MATERIALS AND METHODS:

Chromosomal analysis and hormonal assay were carried out on 223 patients with primary amenorrhea that were referred from different parts of Egypt to Cytogenetic laboratory of Genetic Unit, Children Hospital Mansoura University, from July 2008 to December 2010. FISH technique was carried out in some of cases to more evaluation.

RESULTS:

The frequency of chromosomal abnormalities was 46 (20.63%) in primary amenorrhea patients. The chromosomal abnormalities can be classified into four main types. (1) The numerical abnormalities of the X chromosome were detected in 23 (50 %). (2) Structural abnormalities of the X chromosome were detected in 11 (23.91%). (3) Mosaicism of X chromosome was found in 10 (21.74%). (4) Male karyotype 46, XY was presented in 2 (4.35%).

CONCLUSION:

The present study showed that karyotype and FISH are necessary to detect the causes of primary amenorrhea. This study also revealed the incidence of chromosomal abnormalities in women with primary amenorrhea in Egypt is similar to that reported in previous literatures.     

A unique dicentric X;Y translocation with Xq and Yp breakpoints: cytogenetic and molecular studies.

A 32-year-old woman presented with secondary amenorrhea and infertility. She was of normal height and her breasts were well developed, but she had streak gonads; there were no signs of virilization, and she showed no somatic stigmata of Turner syndrome. Chromosome analysis revealed a dicentric X;Y translocation with Xq and Yp breakpoints. Centromeric banding demonstrated a Y centromere and a "suppressed" X centromere. The karyotype of the patient was interpreted as 46,X,t(X;Y)(q22;p11). The Yp breakpoint was confirmed by DNA-hybridization studies with six probes detecting Y-specific sequences. These DNA-hybridization studies were consistent with the presence of the long arm, centromere, and much of the proximal short arm of the Y. The Y-DNA studies of this female also revealed the absence of the distal short arm of the Y chromosome, to which the testis-determining factor has previously been localized.     

A case of (X;15) translocation diagnosed as a paracentric inversion of Xp: diagnostic revision with FISH.

In 1990 we reported the case of a 17 years old girl with growth retardation, overweight and primary amenorrhea, presenting a de novo chromosomal rearrangement cytogenetically characterized as a paracentric inversion of the short arm of X chromosome. The FISH analyses that were recently performed, revealed that in fact our patient presented a case of unbalanced translocation, 46,X, t(X;15)(p11.2; q15).     

A second case of (de novo) paracentric inversion of the short arm of the X chromosome

A de novo paracentric inversion of the short arm of an X chromosome (p11.2p22.1) was observed in a 17-year-old girl studied because of primary amenorrhea and a Turner phenotype. To our knowledge this is only the second case of a paracentric inversion of the X chromosome short arm reported, the first having been briefly described in 1982, in a young lady with the Turner phenotype. In spite of its balanced appearance, there is little doubt that this rearrangement is the cause of the phenotypic anomalies of the patient, probably as the result of gene(s) modification(s) at the breakpoints on the X chromosome, or because the inverted gene sequence resulted in modifications by position effect. It has become increasingly difficult to recognize obvious phenotype-genotype correlations in Turner syndrome, given the multiplicity of chromosome rearrangements--some of them quite subtle--which are associated with ovarian dysgenesis.     

The phenotypic effects of small,distal Xq deletions

Summary The effects of small, distal Xq deletions (Xq26 qter) have been reviewed in light of three cases of our own and five from the literature. The symptoms caused by such deletions range from apparently none through irregular menstruation to secondary amenorrhea (or premature menopause) to primary amenorrhea. That the abnormal chromosome has any effects when it is inactivated may best be explained by one or by a combination of the following hypotheses. (1) the Xq — chromosome might exert an effect during development when cells in which it is active compete with cells in which it is inactivated, assuming that the inactivation of the two X chromosomes is originally random. (2) a more probable hypothesis is that there is a position effect when a break has occurred in the critical region Xq13q27 which apparently must be intact in both X chromosomes to allow normal development of the ovaries. (3) this position effect might, in turn, affect the oocytes (and thus the ovary) after the inactive X chromosome is reactivated before meiosis or the deletion as such might have a direct effect on the ovaries.     

Cytogenetic investigation of 103 patients with primary or secondary amenorrhea

Cytogenetic investigations were carried out on 103 women presenting with either primary (n = 88) or secondary (n = 15) amenorrhea. A sex chromosome anomaly was found in 26% and 33% of these patients, respectively. Other studies on women with primary amenorrhea have found a similar or even higher percentage of patients with an abnormal karyotype. It is therefore suggested that all women with absence of menstruation after the age of 16 years should be investigated cytogenetically. The surprisingly high percentage of pathological karyotypes among the secondary amenorrhea group does indicate that sex chromosome anomalies cannot be ruled out in women who have had apparently normal ovarian function for at least some time, and therefore more patients from this group should be selected for chromosome analysis.     

On telomere replication and fusion in eukaryotes: apropos of a case of 45,X/46,X,ter rea(X;X)(p22.3;p22.3)

A Mexican 181/2-year-old girl with short stature, primary amenorrhea, and mild Turner stigmata was found to have a 45,X/46,X,ter rea(X;X)(p22.3;p22.3) karyotype in her lymphocytes. The rearranged chromosome was twice the size of a normal X, appeared to be attached head-to-head, had no detectable chromatin loss, only one primary constriction, constitutive heterochromatin at both the centromere and pseudocentromere regions, was mitotically stable, and always showed late replication. From the analysis of this and other X;X terminal rearrangements we draw four conclusions: (1) Terminal rearrangements may arise either by telomeric fusion (tel fus) without loss of genetic material or from a conventional telomeric translocation. (2) Telomeric fusions between homologous chromosomes (the commonest type) can be secondary to impaired telomeric replication. (3) Phenotypically, patients with an X;X terminal rearrangement show great variability which depends mainly on whether or not chromatin has been lost in the rejoining process and a 45,X clone. (4) Patients with an X;X telomeric fusion without mosaicism are likely to have an XXX phenotype, whereas turneroid features are expected in mixoploidies that include an X monosomic clone and in cases of translocations involving the short arms.     

Kinetics of DNA replication in a dicentric X chromosome formed by long arm to long arm fusion

Summary Utilizing the 5-bromo-deoxyuridine (BrdU) incorporation technique, we have recently studied the DNA replication kinetics in a dicentric X chromosome, formed by long arm-to-long arm fusion at band q23, from a 16-year-old black female with primary amenorrhea. The patient has a karyotype 45,X/46,X,dic(X)(q23).In the buccal smear the presence of X chromatin was found in 33% of the cells examined. The Barr bodies are large and 21% of them are bipartite. DNA replication studies were performed on the patient's lymphocytes by the thymidine pulse (T-pulse) method and confirmed comparatively by the BrdU pulse (B-pulse) method. The results indicate that the dicentric X chromosome is always late-replicating. The replication pattern is symmetric on both sides of the breakpoint and the replication sequence is, in order, p11, p22, q1(1–3), q22, q23, p21, and q21. This finding is comparable to those of other investigators and supports the theory that there exist two inactivation centers in the dicentric X chromosome, located on or near the q21 band.     

Molecular cytogenetic characterization of a case of primary amenorrhea with intrachromosomal triplication of the X chromosome q arm

This is a unique case of intrachromosomal triplication of the X chromosome q arm detected with cytogenetic and spectral karyotyping in a 21-year-old woman with primary amenorrhea, who had been referred because of primary hypergonadotropic hypogonadism and Mullerian hypoplasia. Intrachromosomal triplications are rare rearrangements resulting in partial tetrasomy. Since 1993, at least 34 cases of intrachromosomal triplications involving 9 different chromosomes have been reported. The vast majority of the reported triplications are on the 15th chromosome, arised de novo and had middle inverted repetitions. In this report the genotype-fenotype correlation in a case of primary amenorrhea associated with triplication of the X chromosome q arm and the possible mechanisms of this rearrangement are discussed. Further the clinical usability of SKY analysis as a molecular cytogenetic tool in searching for genomic instability arising from cytogenetic rearrangements is highlighted.     

Recombinant chromosome as a result of pericentric inversion of X chromosome

Summary A structural X chromosome abnormality was found in the karyotype of a tall patient with gonadal dysgenesis and with no extragenital anomalies. Based on her mother's karyotype, which showed a pericentric inversion of the X chromosome: 46,X,inv(X)(p22q24), as well as from G and R banding, we concluded that the abnormal X chromosome of our patient was a recombinant chromosome that had originated as a result of one crossing over in the inversion loop during gametogenesis in her mother. The recombinant X chromosome had a partial deletion of Xq and a partial duplication of Xp: 46,X,rec(X),dup p,inv(X)(p22q24). After BUDR incorporation, the abnormal X chromosome of the patient and that of her mother showed a late replication. The karyotype-phenotype correlation and the nonrandom inactivation of the inverted X chromosome in the mother are discussed.     

Multiple cytogenetic methods used to identify a new structural rearrangement of the human X chromosome.

A woman with primary amenorrhea and pure gonadal dysgenesis had two cytogenetically abnormal cell lines. The karyotype was 45,X in 56--95% of mitosis from lymphocytes and skin fibroblasts. In the remaining 5--44% of the cells there was, in addition to a normal X, a structurally abnormal X chromosome interpretable as pter leads to q21::q11 leads to pter or pter leads to q21::q13 leads to pter. The abnormal X chromosome was heterocyclic and had a normal centromere plus an extra C band in the long arm. Detailed interpretation of the structural rearrangements of this chromosome required the use of both Q-, G-, and C-banding and the BrdU-Hoechst 33258 technique.     

Molecular cytogenetic analysis of a duplication Xp in a male: further delineation of a possible sex influencing region on the X chromosome

We describe a male infant with severe mental retardation and autism with a duplication of the short arm of the X chromosome. Chromosome painting confirmed the origin of this X duplication. Molecular cytogenetic analysis with fluorescence in situ hybridization (FISH) identified one copy of the zinc finger protein on the X chromosome (ZFX) and two copies of the steroid sulfatase gene (STS), further delineating the breakpoints. Based on cytogenetic and molecular comparisons of cases from the literature of sex-reversal in dup(X),Y patients and our patient, we suggest that a possible secondary sexinfluencing gene involved in the regulation of sex determination or testis morphogenesis is present at the distal Xp21.1 to p21.2 region.     

Gonadendysgenesie mit ungewöhnlicher Strukturanomalie eines X-Chromosoms (45,X/46,XXq+)

Zusammenfassung Bei einer 29jährigen Frau mit sekundärer Amenorrhoe wurde ein 45,X/46,XXq+-Mosaik gefunden. Der Zellstamm mit der Modalzahl 46 enthielt ein spätreplizierendes abnormes X-Chromsom, das morphologisch der Gruppe B zugeordnet wurde. Die gering ausgeprägten Entwicklungsstörungen und die endokrinologischen Befunde, die auf rudimentäres Ovarialgewebe schließen lassen, werden auf den Effekt der 46/XX+-Zellinie zurückgeführt die, ähnlich einer normalen 46,XX-Zellinie, die Ausprägung der XO-Komponente abschwächt.

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Gonadal dysgenesis with an unusual structural anomaly in an X chromosome (45,X/46,XXq+)

Summary A 45,X/46,XXq+ mosaic was found in a 29-year-old woman with secondary amenorrhea. The cell-line with the modal number 46 contained a late replicating abnormal X chromosome which was morphologically assigned to group B. The slight developmental disturbances and the endocrinological findings, which indicate rudimentary ovarian tissue are ascribed to the effect of the 46,XXq+ cell-line, which, like a normal 46/XX line, weakens the effect of the XO component.

     

Characterization of an X;X translocation by cytological analysis and in situ hybridization

An X;X chromosomal translocation was ascertained by conventional cytogenetic analysis in a phenotypically normal woman with secondary amenorrhea. In situ hybridization was performed with previously mapped X-specific DNA sequences to study the rearrangement at the molecular level. The results allowed us to demonstrate that the subject is monosomic for the distal region of the short arm of the X and trisomic for the distal region of the long arm.