Turner syndrome mosaicism: an unusual case with a de novo large dicentric marker chromosome: mos 45,X/46,X, ter rea(X;X)(p22.3;p22.3)

X/X translocations are quite rare in humans. The effect of this anomaly on the phenotype is variable and depends on the amount of deleted material and whether the chromosomes are joined by their long or short arms. We report an unusual case of Turner syndrome mosaicism in a 16-year-old girl, who was referred to our Institute for primary amenorrhoea associated with short stature. Endocrine evaluation revealed hypergonadotropic hypogonadism, which required a study of the karyotype. Cytogenetic analysis, performed on peripheral blood leucocytes, showed a mos 45,X/46,X,ter rea (X;X)(p22.3;p22.3) de novo karyotype. The prevalent cell line was 45,X (90% cells). A second cell line (10% cells) showed a very large marker chromosome, similar to a large metacentric chromosome. FISH (fluorescent in situ hybridisation) and molecular analysis revealed that the marker chromosome was dicentric and totally derived from the paternal X chromosome.     

Different chromosome Y abnormalities in Turner syndrome.

A 17-year-old phenotypically female girl was referred for evaluation because of short stature and primary amenorrhea. Cytogenetic analysis showed a mosaic 46,XY/45,X/47,XYY/46,X,idic(Yq)/47,XY,idic(Yq)/48,XXY,idic(Yq)/46,X,t(C;Y) karyotype. Conventional cytogenetic results were supplemented with fluorescence in situ hybridization (FISH) techniques to ensure a better characterization of abnormalities. By using FISH, a supernumerary marker chromosome derived from chromosome Y which could not be detected by conventional cytogenetics was revealed. Furthermore, additional abnormalities and their frequencies were highlighted by the application of DNA probes specific for X and Y chromosomes. Thus, FISH proved useful in determining low frequency cell lines which would need analysis of a large number of good quality metaphase spreads by conventional cytogenetic techniques: it helped in identifying the nature and the origin of unknown markers and rearrangements which have important implication in sexual differentiation and development of gonadal tumours.     

Mosaicism in 45,X Turner syndrome: does survival in early pregnancy depend on the presence of two sex chromosomes?

Summary Cytogenetic and molecular genetic findings in 91 patients with Turner syndrome are reported. In 87 patients, chromosome studies were carried out both in lymphocyte and fibroblast cultures. Mosaicism was demonstrated in 58 of these patients (66.7%), whereas only 18 (20.7%) were apparent non-mosaic 45,X, and 11 patients (12.6%) showed non-mosaic structural aberrations of the X chromosome. Among the mosaic cases 16 (18.4% of all patients) displayed a second cell line containing small marker chromosomes. The association of Y-specific chromosomal material with the presence of marker chromosomes was demonstrated in 6 out of 7 mixoploid fibroblast cell lines by polymerase chain reaction amplification and by Southern-blot analysis. The observation of ring formation and morphological variability in vivo and in vitro, and the continous reduction in the percentage of cells containing marker chromosomes in longterm cultivation experiments indicated an increased instability of marker chromosomes. The findings suggest that in vivo selection of structurally altered sex chromosomes exists. Thus, the observation of apparent non-mosaic 45,X chromosomal complements in liveborn individuals with Turner syndrome does not contradict the hypothesis that some degree of mosaicism is necessary for survival in early pregnancy.     

A possible exception to the critical region hypothesis.

Cytogenetic studies were done on a 5-year-old female with multiple congenital anomalies and mental retardation, revealing an unbalanced X/11 translocation. Her mother and phenotypically normal sister carry the balanced form of the translocation, while her brother has a normal 46,XY karyotype. Banding studies showed the breakpoints to be Xq22 and 11q13. These are remarkable for the following reasons: (1) the X breakpoint is within the critical region of the X chromosome, yet the balanced carrier does not manifest gonadal dysgenesis; and (2) the proband was trisomic for most of the long arm of chromosome 11. Late-replication studies of cells from the two balanced carriers showed inactivation of the normal X.     

Cytogenetic abnormalities in Tunisian women with premature ovarian failure

To identify the distribution of chromosome abnormalities among Tunisian women with premature ovarian failure (POF) referred to the department of Cytogenetic at the Pasteur Institute of Tunis (Tunisia), standard cytogenetic analysis was carried out in a total of 100 women younger than 40 affected with premature ovarian failure. We identified 18 chromosomal abnormalities, including seven X-numerical anomalies in mosaic and non-mosaic state (45,X; 47,XXX), four sex reversal, three X-structural abnormalities (terminal deletion and isochromosomes), one autosomal translocation and one supernumerary marker. The overall prevalence of chromosomal abnormalities was 18% in our cohort. X chromosome aneuploidy was the most frequent aberration. This finding confirms the essential role of X chromosome in ovarian function and underlies the importance of cytogenetic investigations in the routine management of POF.     

Cytogenetic findings in Serbian patients with Turner's syndrome stigmata

Cytogenetic findings are reported for 31 female patients with Turner's syndrome. Chromosome studies were made from lymphocyte cultures. Non-mosaicism 45,X was demonstrated in 15 of these patients, whereas only three were apparently mosaic. Eight patients showed non-mosaic and four patients showed mosaic structural aberrations of the X-chromosome. One non-mosaic case displayed a karyotype containing a small marker chromosome. Conventional cytogenetics was supplemented by fluorescence in situ hybridization (FISH) with an X-specific probe to identify the chromosomal origin of the ring and a 1q12-specific DNA probe to identify de novo balanced translocation (1;9) in one patient. To our knowledge, this is the first finding of karyotype 45,X,t(1;9)(cen;cen)/46,X,r(X),t(1;9)(cen;cen) in Turner's syndrome. The same X-specific probe was also used to identify a derivative chromosome in one patient.     

Transmission of the marker X syndrome trait by unaffected males: Conclusions from studies of large families

Summary It is well established that apparently unaffected males can be transmitters of the marker X syndrome trait. Cytogenetic and clinical investigations of these male transmitters are only rarely reported for most of these male transmitters are dead by the time the syndrome is diagnosed in their families. We report on cytogenetic and clinical investigations of two unaffected male carriers of the disorder from two large families. Pedigree analysis of these families revealed six other cases of possible male transmission of the marker X syndrome trait. Mental impairment was not reported from the siblings of these unaffected male carriers and could not be observed in their daughters. The mode of transmission of the disorder cannot be fully explained by X-linked inheritance. The phenomenon of unaffected males transmitting the disorder could be due to an autosomal suppressor systeme. Our findings indicate that male transmission may be important for the frequency of the disorder.     

A 39,X/40,XY/41,XYY mosaic male mouse

Cytogenetic analyses of bone marrow and gonadal cells in a male mouse, which appeared to be normal, revealed mosaicism in both tissues. Three chromosome complements, 39,X, 40,XY, and 41,XYY, were found in both bone marrow and spermatogonia, while only the last two complements were found in spermatocytes. In this mouse, unlike in the human, the XYY cells showed a proliferative advantage over the XY cells. In XYY cells at diakinesis/metaphase I the gonosomes showed all possible types of association, and a pairing advantage of the X chromosome was clearly demonstrated. The fertility of the mouse was not determined. However, since the epididymal sperm count was reduced by only 55% and the incidence of sperm head abnormality was near normal, it is not evident that the mouse was sterile.     

The most frequent chromosomal abnormalities in karyotypes of patients with reproductive disorders

Cytogenetic and molecular cytogenetic characteristics have been studied in 210 couples with fertility problems. The patients’ karyotypes contained various chromosomal rearrangements in 46 cases (10.95%). The structural chromosomal rearrangements such as pericentric inversions, Robertsonian translocations, balanced reciprocal translocations, and marker chromosomes were more frequent than numerical chromosome aberrations (89.13 and 10.87% of cases, respectively). We have found 19 (4.52%) karyotypes with “hidden’ low mosaicism in X and Y chromosomes. We believe that the patients with chromosomal anomalies in the karyotype need differentiated treatment.     

Two cases of infertile bitches with 78,XX/77,X mosaic karyotype: a need for cytogenetic evaluation of dogs with reproductive disorders

A mosaic karyotype 78,XX/77,X was found in two infertile purebred dogs. Cytogenetic investigations were carried out on a large number of metaphase spreads (220 and 473) with the use of conventional Giemsa staining, C-banding, and chromosome painting approaches. The frequencies of the monosomic spreads (77,X) were low: 5.3% and 5.6%. We recommend that at least 90 metaphase spreads be analyzed to allow possible detection of low-level XX/X mosaicism, and we discuss the need for cytogenetic evaluation of dogs with reproductive disorders.     

A 47,XXY female with unusual genitalia

A 47,XXY karyotype was found in a 6-year-old girl. The patient had female external genitalia, clitoromegaly, remnants of the ductus mesonephricus, uterus, and gonads in the labia majora which were determined to be testes by histology. Cytogenetic and DNA analyses suggest that the Y chromosome had a normal structure and that both X chromosomes were of maternal origin. The unusual clinical findings in the patient are discussed.Dedicated to Professor Ulrich Wolf on the occasion of his 60th birthday     

Rapid detection of sex chromosomal aneuploidies by QF-PCR: application in 200 men with severe oligozoospermia or azoospermia

Klinefelter syndrome is the most common genetic cause of severe male factor infertility. Cytogenetic evaluation of metaphase chromosomes generally has a long turnaround time. We describe a reliable molecular genetic method that can be completed in 2 working days to identify the presence of any extra X chromosomes. The quantitative fluorescent (QF) 5-plex PCR includes the amplification of amelogenin, which is present on both sex chromosomes in a biallelic form, a polymorphic short tandem repeat (STR) on the pseudoautosomal region of X and Y (X22), two polymorphic X-specific STRs (DXS6803, DXS6809), and a Y-specific marker (SY134), in a single tube. The presence of an extra X chromosome is recognized either by a supernumerary peak or an increased peak area based on criteria we have developed. The application of the method on 200 patients resulted in the identification of 14 patients (7%) with Klinefelter syndrome or a variant form (2 SRY-positive 46,XX men), as well as an additional patient with 47,XYY karyotype. The QF-PCR method, along with Y chromosome microdeletion testing, can be used as a first-step genetic analysis in azoospermic or severely oligozoospermic patients for the rapid identification of sex chromosome aneuploidies.     

Cytogenetic study of malignant histiocytosis transplanted into nude mice; presence of translocation between chromosomes 5 and 6 and a unique marker (13q+)

Fluid from a pleural effusion in a child with malignant histiocytosis was grafted into nude mice. Cytogenetic studies were performed on the xenografted cells which revealed a diploid karyotype with a translocation t (5;6) and a marker (13q+). This study reports a new rearrangement which has not been described previously in malignant histiocytosis.     

Gene mapping in Mus musculus by interspecific cell hybridization: assignment of the genes for tripeptidase-1 to chromosome 10, dipeptidase-2 to chromosome 18, acid phosphatase-1 to chromosome 12, and adenylate kinase-1 to chromosome 2.

Chinese hamster X mouse somatic cell hybrids segregating mouse chromosomes were examined for their mouse chromosome content using trypsin-Giemsa (GTG) banding and Hoechst 33258 staining techniques. Simultaneously, they were scored for the presence of 24 mouse enzymes. The results confirm the assignments of 11 genes previously mapped by sexual genetics: Dip-1 and Id-1 to chromosome 1; Pgm-2 and Pgd to 4; Pgm-1 to 5; Gpi-1 to 7; Gr-1 to 8; Mpi-1 and Mod-1 to 9; Np-1 and Es-10 to 14. They also confirm chromosomally the assignments of 3 genes that were made by other somatic cell genetic studies: Aprt to 8; Hprt and alpha-gal to the X chromosome. But most importantly, four enzyme loci are assigned to four chromosomes that until now were not known to carry a biochemical marker which is expressed in cultured cells: Trip-1 to 10; Dip-2 to 18; Acp-1 to 12; and Ak-1 to 2. Cytogenetic examination of clones showing discordant segregation of HPRT and A-GAL, suggested the assignment of alpha-gal to region XE leads to XF of the mouse X chromosome. The cytologic studies provide a comparison between data from sexual genetics and somatic cell hybrids and validate hybrid cell techniques. They provide evidence of the reliability of scoring chromosomes by GTG and Hoechst staining and stress the importance of identifying clones with multiple chromosome rearrangements. Striking examples of norandom segregation of mouse chromosomes were observed in these hybrids with preferential retention of 15 and segregation of 11 and the Y chromosome.     

Chromosome evolution involving Robertsonian rearrangements in Xyrichthys fish (Labridae, Perciformes)

Three Xyrichthys fish (Labridae, Perciformes), X. pavo, X. dea, and X. twistii, were cytogenetically studied. X. pavo and X. dea had 2n = 44 chromosomes, which were all acrocentric. X. twistii had 2n = 22 chromosomes consisting of eighteen meta- and submetacentric and four acrocentric chromosomes. The cellular DNA contents of X. pavo and X. twistii measured using flow cytometry were nearly equal. These results suggest that the karyotype of X. twistii evolved by decreasing the number of chromosomes by fusion events, probably Robertsonian fusion. Cytogenetic relationships among the three species were surmized on the basis of features on the karyotypes and the NOR locations. A large gap in the chromosome number between 2n = 44 and 2n = 22 is an interesting feature related to the process of chromosome evolution.     

Identification of the short arm of the Y chromosome by cytogenetic and molecular analyses

Isochromosome Y is one of the structural anomalies of the Y chromosome associated with a 45,X cell line and a broad spectrum of phenotypes. We present a case of de novo 46,X,+mar detected in a 17-yearold male patient. He had shortening of the right leg, bilateral breast enlargement, pubic, underarm and facial hair development, small penis and testicles, low serum cortisol, ACTH and total testosterone levels, normal LH value, high FSH value, normal testicles and epididymis, minimal left varicocele. The chromosome aberration was detected by cytogenetic analysis. Cytogenetic and molecular analysis was performed by conventional karyotyping and quantitative florescence PCR, respectively. The molecular analyses by PCR detected the presence of the SRY and AMXY genes, confirming the presence of the short arm of the Y chromosome. PCR demonstrated that the marker chromosome is of Y origin and corresponds to an authentic isochromosome for the short arm of the Y chromosome, i(Yp). We suggest that the structural alteration of the Y chromosome was a new mutation, which occurred in the initial mitotic division of the embryo, originally 46,XY. The result of accurate evaluation provides correct sex assignment and the prevention of the neoplastic degeneration of a dysgenetic gonad. The karyotype 46,X,i(Yp) indicates that the patient is preserving the SRY gene.     

A jumping sex determining factor in the flyMegaselia scalaris

To test earlier reports on changes of the sex determining linkage group inMegaselia scalaris, we used a combination of a cytogenetic and a phenotypic marker in a laboratory strain as a detection system for rare cases in which linkage of the marker and the Y chromosome was disrupted. From some of the exceptional males detected in this system we established strains with a different chromosome pair acting as the sex chromosome pair. Cytogenetic analysis, crossbreeding tests with a phenotypic marker and DNA blot hybridization with cloned DNA probes indicated that an epistatic male determining factor had moved to one of the former autosomes at a frequency of at least 0.06%.     

A novel Robertsonian translocation in a family of Walker hounds.

A 5-year-old female Walker hound was presented to the Washington State University Veterinary Teaching Hospital as a result of a narrowing of the vulva, which prevented natural breeding. All other physical and clinical findings were normal. Cytogenetic analysis disclosed a chromosome number of 77, with three metacentric chromosomes comprised of two X chromosomes and a Robertsonian translocation of two acrocentric autosomes, chromosomes 21 and 33. Cytogenetic analysis of two full-sister siblings with histories of absence of estrus disclosed one with the same translocation and one with a normal female chromosome constitution. The propositus was artificially inseminated with semen from a karyotypically normal male Walker hound and gave birth to nine live grossly normal pups, six females and three males. Another female pup was stillborn but was grossly normal. Cytogenetic analysis of the live pups disclosed that four (three males and one female) of the nine had the same translocation in all lymphocytes. The remaining five pups (five females) had normal female chromosome constitutions. The litter size was average for this breed. This is a previously unreported Robertsonian translocation in dogs.     

135例无精症患者的细胞遗传学分析：附1例世界首报染色体异常核型

本文对来我室咨询的１３５例无精症患者进行了细胞遗传学分析,发现异常核型３８例,其中４７,ＸＸＹ,ｔ（６;９）（ｐ２１;ｑ２２）为世界首报核型。本文对异常核型与无精症之间的关系进行探讨