Molecular analysis of Y chromosome long arm structural instability in patients with gonadal dysfunction

Prenatal diagnosis of sex chromosome mosaicism with two marker chromosomes in three cell lines and a review of the literature

The present study described the diagnosis of a fetus with sex chromosome mosaicism in three cell lines and two marker chromosomes. A 24‑year‑old woman underwent amniocentesis at 21 weeks and 4 days of gestation due to noninvasive prenatal testing identifying that the fetus had sex chromosome abnormalities. Amniotic cell culture revealed a karyotype of 45,X[13]/46,X,+mar1[6]/46,X,+mar2[9], and prenatal ultrasound was unremarkable. The woman underwent repeat amniocentesis at 23 weeks and 4 days of gestation for molecular detection. Single nucleotide polymorphism (SNP) microarray analysis on uncultured amniocytes revealed that the fetus had two Y chromosomes and 7.8‑Mb deletions in Yq11.222q12. The deletion regions included DAZ, RBMY and PRY genes, which could cause spermatogenesis obstacle and sterility. Interphase fluorescence in situ hybridization (FISH) using centromeric probes DXZ1/DYZ3/D18Z1 was performed on uncultured amniocytes to verify the two marker chromosomes to be Y chromosome derivatives. According to these examinations, the mar1 was identified as a derivative of the Y chromosome with a deletion in Yq11.222q12, and the mar2 was identified as a dicentric derivative of the Y chromosome. The molecular karyotype was therefore 45,X,ish(DXZ1+, DYZ3‑,D18Z1++)[5]/46,X,del(Y)(q11.222),ish(DXZ1+,DYZ3+,D18Z1++)[11]/46, X,idic(Y)(q11.222),ish(DXZ1+,DYZ3++,D18Z1++)[14]. The comprehensive use of cytogenetic, SNP array and FISH detections was advantageous for accurately identifying the karyotype, identifying the origin of the marker chromosome and preparing effective genetic counseling.

Sex Chromosome Mosaicism in the Gonads of DSD Patients: A Karyotype/Phenotype Correlation

Sex chromosome mosaicism results in a large clinical spectrum of disorders of sexual development (DSD). The percentage of 45,X cells in the developing gonad plays a major role in sex determination. However, few reports on the gonadal mosaic status have been published, and the phenotype is usually correlated with peripheral lymphocyte karyotypes, which makes the phenotype prediction imprecise. This study was conducted on 7 Egyptian DSD patients to demonstrate the effect of sex chromosome constitution of both blood lymphocytes and gonadal tissues on the phenotypic manifestations. Conventional cytogenetic and FISH analyses of blood lymphocytes were conducted, and laparoscopy with gonadal biopsy was performed for histopathologic examination and FISH analysis. Gonosomal mosaicism was detected in 3 patients who had a non-mosaic chromosome pattern in blood lymphocytes. Two patients showed the same type of sex chromosome mosaicism in both the blood and gonadal tissues but with different distributions. Two other patients revealed a non-mosaic pattern in both tissues. The present study elucidates the importance of examining sex chromosome mosaicism in gonadal tissues of DSD patients and highlights the critical role of 45,X mosaicism which can lead to serious effects during early gonadal organogenesis.

Correlation of intercentromeric distance, mosaicism, and sexual phenotype: molecular localization of breakpoints in isodicentric Y chromosomes

Isodicentric chromosomes are among the structural abnormalities of the Y chromosome that are commonly identified in patients. The simultaneous 45,X cell line that is generated in cell division due to instability of the isodicentric Y chromosome [idic(Y)] has long been hypothesized to explain the variable sexual development of these patients, although gonads have been studied in only a subset of cases. We report here on the molecular localization of breakpoints in ten patients with an idic(Y). Breakpoints were mapped by FISH using BACs; gonads and fibroblasts were also analyzed when possible to evaluate the level of mosaicism. First, we demonstrate great tissue variability in the distribution of idic(Y). Second, palindromes and direct repeats were near the breakpoint of several idic(Y), suggesting that these sequences play a role in the formation of idic(Y). Finally, our data suggest that intercentromeric distance has a negative influence on the stability of idic(Y), as a greater proportion of cells with breakage or loss of the idic(Y) were found in idic(Y) with a greater intercentromeric distance. Females had a significantly greater intercentromeric distance on their idic(Y) than did males. In conclusion, our study indicates that the Y chromosome contains sequences that are more prone to formation of isodicentric chromosomes. We also demonstrate that patients with an intercentromeric distance greater than 20 Mb on their idic(Y) are at increased risk of having a female sexual phenotype.

Germ cell tumor showing partial trisomy 1 in a gonadectomized intersex child with monosomy X and double Y mosaicism

High incidence of germ cell tumors arising from dysgenetic gonads in patients with sexual chromosome abnormalities has been described, especially in patients with a Y chromosome bearing cell line. Here we report a 14-year-old patient with ambiguous genitalia. Constitutional karyotype showed 45,X/46,X,derY [?t(Yp;Yq)] mosaicism. The patient developed an abdominally located mixed malignant germ cell tumor 5 years after the removal of the dysgenetic gonads. Tumor karyotype showed partial trisomy 1q, a derivative 8q, and a hyperdiploidy with +X, +7, +12, +15, +19, +21, and an unidentified marker.

Clinical and molecular cytogenetic studies in three infertile patients with mosaic rearranged Y chromosomes

Isodicentrics (idic) are structural anomalies of the Y chromosome associated with a 45,X cell line and a broad spectrum of phenotypes. We characterized the rearranged Y chromosomes from three azoospermic males by fluorescence in-situ hybridization (FISH) and PCR. Chromosome study was performed on lymphocytes and testicular biopsy. FISH analysis and PCR established the degree of mosaicism and analysed specific Y regions. Two patients showed a 45,X/46,X,?idic(Y) karyotype with varying degrees of mosaicism. FISH demonstrated the presence of two centromeres and two SRY regions. In the lymphocytes of the third patient, the presence of a small Y-derived marker was also observed. An additional cell line with two idic(Y) was present in the testicular biopsy of the same patient. PCR showed the breakpoint between SY182 (KALY) and SY121 in Yq11.221-q11.222 region in all the cases. For the evaluation of the mosaicism, different tissues must be investigated. The phenotypical sex depends more on the number of copies of the SRY gene rather than on the percentage of 45,X cells, at least in the gonads. The combined use of classical and molecular cytogenetics is necessary for delineating the chromosome regions involved allowing a better genotype-phenotype correlation.

Cytogenetic and molecular characterization of two isodicentric Y chromosomes

We report the results of detailed molecular-cytogenetic studies of two isodicentric Y [idic(Y)] chromosomes identified in patients with complex mosaic karyotypes. We used fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR) to determine the structure and genetic content of the abnormal chromosomes. In the first patient, classical cytogenetics and FISH analysis with Y chromosome-specific probes showed in peripheral blood lymphocytes a karyotype with 4 cell lines: 45,X[128]/46,X,+idic(Y)(p11.32)[65]/47,XY,+idic(Y)(p11.32)[2]/47,X,+2idic(Y)(p11.32)[1]. No Y chromosome material was found in the removed gonads. For precise characterization of the Yp breakpoint, FISH and fiberFISH analysis, using a telomeric probe and a panel of cosmid probes from the pseudoautosomal region PAR1, was performed. The results showed that the breakpoint maps approximately 1,000 Kb from Ypter. The second idic(Y) chromosome was found in a boy with mild mental retardation, craniofacial anomalies, and the karyotype in lymphocytes 47,X,+idic(Y)(q11.23),+i(Y)(p10)[77]/46,X,+i(Y)(p10)[23]. To our knowledge, such an association has not been previously described. FISH and PCR analysis indicated the presence of at least two copies of the SRY gene in all analyzed cells. Using 17 PCR primers, the Yq breakpoint was shown to map between sY123 (DYS214) and sY121 (DYS212) loci in interval 5O in AZFb region. Possible mechanisms of formation of abnormal Y chromosomes and karyotype-phenotype correlations are discussed.