Distribution Of Sex Chromosomes Research Articles

Distribution of the sex chromosome during mouse spermatogenesis in testis tissue sections.

During mammalian spermatogenesis, spermatogenic cells undergo mitotic division and are subsequently divided into haploid spermatids by meiotic division, but the dynamics of sex chromosomes during spermatogenesis are unclear in vivo. To gain insight into the distribution of sex chromosomes in the testis, we examined the localization of sex chromosomes before and after meiosis in mouse testis sections. Here, we developed a method of fluorescence in situ hybridization (FISH) using specific probes for the X and Y chromosomes to obtain their positional information in histological testis sections. FISH analysis revealed the sex chromosomal position during spermatogenesis in each stage of seminiferous epithelia and in each spermatogenic cell. In the spermatogonia and leptotene spermatocytes, sex chromosomes were distantly positioned in the cell. In the zygotene and pachytene spermatocytes at prophase I, X and Y chromosomes had a random distribution. After meiosis, the X and Y spermatids were random in every seminiferous epithelium. We also detected aneuploidy of sex chromosomes in spermatogenic cells using our developed FISH analysis. Our results provide further insight into the distribution of sex chromosomes during spermatogenesis, which could help to elucidate a specific difference between X and Y spermatids and sex chromosome-specific behavior.

Distribution of sex chromosomes (XY) in lymphocyte metaphase spreads of dairy bulls

Position of autosome and sex chromosomes in metaphase spreads is grate concerned of Cytogeneticians worldwide to understand cell biology. A few isolated studies have been conducted for the distribution of chromosomes in metaphase spread. Our studies reveal that most sex chromosomes (XY) remain on periphery and semi-periphery, 84.16% for X and 86.97% for Y respectively, in round metaphase spreads. The application of sex chromosome position in metaphase spreads is to easily find out sex chromosomes under microscope even without banding patterns. An another application is to identify or confirm sex chromosomes in unknown species on which cytogenetic studies have not been performed.

A successful second delivery outcome using refrozen thawed testicular sperm from an infertile male true hermaphrodite with a 46, XX/46, XY karyotype: case report

We report a successful second delivery of a healthy infant fathered using refrozen thawed testicular sperm from an infertile male chimera. We also examined sex chromosome distribution of the seminiferous tubule. Intracytoplasmic sperm injection (ICSI) was performed using the remaining refrozen testicular sperm, which had been stored during the first treatment. Biopsied testicular cells were examined by fluorescence in situ hybridization (FISH) and the peripheral lymphocyte karyotype was tested using a G-band. Following ICSI, a second pregnancy was established, and a healthy girl was successfully delivered at 40 gestational weeks without complications. Although the husband's lymphocyte chromosomal analysis revealed a 46, XX [28]/46, XY [2] karyotype, the seminiferous tubule cells on histological examination by FISH were chimeric sex chromosome type XX [18]/XY [82]. In conclusion, this is a very rare case report of a successful subsequent delivery of a healthy infant (46, XX) from an infertile true hermaphrodite (46, XX/46, XY) using refrozen thawed testicular sperm. The seminiferous tubule cells' karyotype ratio differed from that of the lymphocytes.

A possibility of unbiased sex preselection in humans by enrichment of X or Y chromosome bearing spermatozoa.

Human sex ratio is generally 1.06. The motility selected population of spermatozoa are usually Y chromosome rich. It is therefore easier to influence selected male births. Social and psychologic factors and economic needs intensified by high technology may cause further imbalance in the sex-ratio, creating a demand for techniques to influence sex selection. Such techniques may also help to handle sex linked defects. An examination of several studies on the sex chromosome distribution of human spermatozoa, based on HOP method, showed a preponderance of either X or Y bearing male pronuclei, depending on certain experimental conditions, indicating a technical possibility of influencing sex in an unbiased way.

Distribution of sex chromosomes in dysgenetic gonads of mixed type

In a four-week-old child with female external and internal genitalia but with clitoris hypertrophy chromosome analysis from blood lymphocytes revealed a 46,XY karyotype. No deletion of Y chromosomal sequences was detected by PCR analysis of genomic DNA isolated from peripheral blood leucocytes. Because of the increased risk for gonadal tumours, gonadectomy was performed. Conventional cytogenetic analysis of the left dysgenetic gonad revealed a gonosomal mosaicism with a 45,X cell line in 27 of 50 metaphases. The dysgenetic left gonad demonstrated a significantly higher proportion (P = 0.005) of cells carrying a Y chromosome (46.3%) than the streak gonad from the right side (33.9%). Histomorphological examination of the left gonad revealed immature testicular tissue and rete-like structures as well as irregular ovarian type areas with cystic follicular structures. Interphase FISH analysis of the different tissues of this dysgenetic gonad demonstrated variable proportions of cells with an X and a Y chromosome. Whereas Sertoli cells and rete-like structures revealed a significantly higher proportion of XY cells in relation to the whole section of the dysgenetic gonad (P < 0.0001), almost all granulose-like cells carried no Y chromosome. The proportion of XY/X cells in theca-like cells and Leydig cells was similar to that of the whole dysgenetic gonad. In contrast to these findings, spermatogonia exclusively contained an XY constellation.

Male pseudohermaphroditism and gonadal mosaicism in a 47,XY,+22 fetus

Trisomy 22 syndrome manifestations include cranial and facial anomalies. Ambiguous genitalia have been described in some fetus, but histological examination of the gonads has been rarely provided. We report here the first case of a male pseudohermaphrodite fetus with non-mosaic full trisomy 22 in amniocytes and presenting with ambiguous external genitalia, testes, and a uterus. In this case, we have further analyzed cytogenetically gonadal and uterine tissues. FISH analyses on paraffin-embedded gonads and uterus indicated the presence of two cell lines: XY and monosomy X, with 22%-50% of uterine cells having monosomy X, while 85%-100% of right and 77%-96% of left testicular cells were XY. The distribution of sex chromosomes observed in these tissues could explain the sexual differentiation observed in this fetus. On the other hand, this phenotype could also have resulted from cryptic anomalies in one or several genes implicated in sexual differentiation. Further evidence is thus needed before identifying the true cause of pseudohermaphroditism in our patient.

From spermatocytes to spermatozoa in an infertile XYY male

Sex chromosome distribution and aneuploidy as well as germ cell degeneration were evaluated in meiotic and post-meiotic cells from an infertile XYY male. Sex chromosome distribution was assessed by multicolour fluorescence in situ hybridization on meiotic preparations. Post-meiotic cell aneuploidy was characterized by a method combining multicolour fluorescence in situ hybridization and immunocytochemistry using the proacrosin-specific monoclonal antibody (mAb 4D4). TUNEL assay was carried out on seminiferous tubules to evaluate germ cell degeneration. At the prophase stage of the first meiotic division, 63.64% of cells at the pachytene stage carried three sex chromosomes. The ratio of X-bearing to Y-bearing spermatids and spermatozoa differed significantly from 1 : 1 with an excess of Y-bearing spermatids and spermatozoa. The frequency of hyperhaploid XY spermatids was increased in the XYY male, as well as the incidence of YY, XY and disomic 18 ejaculated spermatozoa. A preferential elimination of germ cells by apoptosis occurred in spermatocytes I. The persistence of the extra Y chromosome during meiosis of an XYY male is associated with a high rate of spermatocyte I degeneration and a low rate of aneuploid spermatozoa.

Numerical sex chromosome aberrations in juvenile angiofibromas: Genetic evidence for an androgen-dependent tumor?

Juvenile angiofibromas (JAs) are rare benign tumors arising almost exclusively in the posterior nasal cavity of adolescent males. While male sex predominance and tumor manifestation during adolescence are well known clinical features, their genetic causes are still unknown. Observation of an increased androgen binding rate to the cytosol of JAs and immunohistological finding of strong AR expression have suggested involvement of the androgen receptor (AR) in JA biology. In the present study, we investigated sex chromosome distribution and the expression of the AR gene in JAs of 7 males using two-color in situ hybridizations. Probes specific for the centromeres of chromosomes 1, X, and Y as well as a probe specific for the AR gene were used for investigation of paraffin-embedded JA tissue. Significant aberrations of the chromosome 1 were not observed. In 6 out of 7 analysed JAs derived from male patients we observed a significant loss of the chromosome Y in 11.5 to 63.8% (mean value: 31.3%). A gain of chromosome X was seen in 5 out of 7 JAs with the finding of two chromosomes X in 12 to 34% (mean value: 25%) of the analyzed nuclei. As each chromosome X revealed nearly almost one AR gene signal without evidence for amplifications, in 11.5 to 30% of the JA nuclei (mean value: 23.8%) two copies of the AR gene were observed. Our data indicate a significant loss of chromosome Y in combination with a gain of chromosome X in JAs. A gain of chromosome X leads to AR gene gain indicating that JAs are androgen-dependent tumors. This is supported by the finding that beta-catenin known to be overexpressed in JAs acts as a co-activator of the AR.

Chromosomal analysis of multipronuclear zygotes obtained after partial zona dissection of the oocytes.

We have attempted to analyse the chromosome constitution of multipronuclear 1-cell zygotes obtained after partial zona dissection (PZD) of the oocytes. Six cells with three pronuclei could not be evaluated whereas another one was characterized by the presence of a normal haploid and two uninterpretable metaphases. Complete karyotypes were established for 21 tripronuclear cells, taking the varying arrangement of the chromosome sets into consideration. Of the zygotes, 10 showed three separated haploid metaphases (distribution pattern n/n/n), eight zygotes had one haploid and one diploid chromosome set (n/2n) and in three cells the individual sets were not distinguishable (3n). The sex chromosome ratio XXX:XXY:XYY was 7:9:5. Chromosome abnormalities were found in eight of the completely or partially analysable tripronuclear zygotes (36.4%) and included numerical (4 cells), structural (2 cells) as well as combinations of numerical and structural alterations (2 cells). Three out of 11 zygotes with four pronuclei could not be evaluated at all. In three cases, only two chromosome sets were analysable and another cell displayed one uninterpretable set. Three out of eight completely or partially analysable zygotes with four pronuclei (37.5%) had chromosomal abnormalities. Excluding the four cells with one or two uninterpretable metaphases, the sex chromosome distribution XXXX:XXXY:XXYY:XYYY in the zygotes with four pronuclei was 0:1:1:2. Compared with previously analysed multipronuclear zygotes obtained after conventional in-vitro fertilization (IVF), the rate of aberrant zygotes as well as the incidence of aberrant (male + female) chromosome sets were not significantly changed after PZD.

The chromosomal constitution of multipronuclear zygotes resulting from in-vitro fertilization.

We have attempted to analyse the chromosome constitution of 77 multipronuclear uncleaved zygotes obtained from our in-vitro fertilization programme. Complete karyotypes could be established for 51 tripronuclear cells and eight zygotes with four pronuclei. When compiling the results, the varying arrangement of the chromosome sets was taken into consideration. Eighteen tripronuclear zygotes showed three separate haploid metaphases (distribution pattern n/n/n), 16 cells had one haploid and one diploid chromosome set (n/2n), and in 15 zygotes the individual sets were not distinguishable (3n). Two zygotes were in fact tetraploid, the distribution of metaphases on the slide being n/3n and n/n/2n, respectively. In tripronuclear zygotes the sex chromosome ratio XXX:XXY:XYY was 14:16:18, excluding the two tetraploid cells and one zygote with a 23,X/23,X/22,-C or -Y karyotype. Chromosome abnormalities were found in 16 zygotes (31.4%) and included numerical (six cells), structural (four cells) as well as combinations of numerical and structural alterations (six cells). Four of the zygotes with four pronuclei (50%) had numerical and/or structural chromosome aberrations. Excluding two cells with one uninterpretable metaphase and a 22,-C or -Y karyotype, respectively, the sex chromosome distribution XXXX:XXXY:XXYY:XYYY was 1:1:2:1 in zygotes with four pronuclei. Another zygote was found to be pentaploid after fixation. These results suggest that analysis of multipronuclear zygotes yields valuable information about cytogenetic abnormalities occurring at the earliest stage of conception.

Spatial distribution of sex chromosomes and ribosomal genes: a study on human lymphocytes and testicular cells.

The location of the sex chromosomes in relation to the rRNA genes in the nuclei of human lymphocytes and testicular cells was examined. Sex chromosomes were found to be located closer to ribosomal genes than would be expected assuming a random arrangement of these chromosomes with respect to rRNA genes. This proximity could be observed irrespective of the transcriptional activity of ribosomal genes indicating that the chromosomal material and not transcriptional activity is responsible for the intranuclear order of these chromosomes.

A fluorescentin situhybridization analysis of the chromosome constitution of ejaculated sperm in a 47, XYY male

Two semen samples from a 47,XXY male were examined using chromosome-specific DNA probes and fluorescent in situ hybridization (FISH) to determine the distribution of sex chromosomes and an autosome (chromosome 17) in the sperm. A motile population of sperm was also prepared from one sample using the swim-up technique to compare the motile and total sperm populations. Chromosomes were localized using single FISH and a biotinylated chromosome 17 probe (TR17), or double FISH using a biotinylated X chromosome probe (TRX) and a digoxigenin-labelled Y chromosome probe (HRY). Labelling efficiencies were 95-98%. Ploidy levels were estimated by measurement against a microscope eye-piece graticule. The overall ratio of X- to Y-bearing sperm was 47% to 48.4% in the neat samples, and 48.4% to 45.3% in the swim-up fraction. Neither of the ratios was significantly different from 1:1. The frequencies of monosomic and disomic (but otherwise haploid sperm) were not different from the frequencies we observed in normal donors. In contrast, the frequencies of both diploid and tetraploid cells were increased in the neat samples of the XYY male. In the swim-up fractions, however, none of these parameters differed from those of ten normal semen donors. These results support the hypothesis that the extra Y chromosome in XYY men is eliminated during spermatogenesis.

Sex chromosome positions in human interphase nuclei as studied by in situ hybridization with chromosome specific DNA probes.

Two cloned repetitive DNA probes, pXBR and CY1, which bind preferentially to specific regions of the human X and Y chromosome, respectively, were used to study the distribution of the sex chromosomes in human lymphocyte nuclei by in situ hybridization experiments. Our data indicate a large variability of the distances between the sex chromosomes in male and female interphase nuclei. However, the mean distance observed between the X and Y chromosome was significantly smaller than the mean distance observed between the two X-chromosomes. The distribution of distances determined experimentally is compared with three model distributions of distances, and the question of a non-random distribution of sex chromosomes is discussed. Mathematical details of these model distributions are provided in an Appendix to this paper. In the case of a human translocation chromosome (Xqter----Xp22.2::Yq11----Yqter) contained in the Chinese hamster X human hybrid cell line 445 X 393, the binding sites of pXBR and CY1 were found close to each other in most interphase nuclei. These data demonstrate the potential use of chromosome-specific repetitive DNA probes to study the problem of interphase chromosome topography.

The induction of sex-chromosomal nondisjunction and diploid spermatids following X-irradiation of pre-spermatid stages in the Northern vole Microtus oeconomus

Chromosome nondisjunction seems to be one of the most important mutagenic effects occuring in man and makes an enormous contribution to human foetal wastage. As yet, little or no information is available on which environmental factors are important in inducing nondisjunction and accordingly we have investigated the effect of X-irradiation on inducing non-disjunction in male germ cells of an experimental mammal, the Northern vole — Microtus oeconomus. Using a staining technique based upon the presence of heterochromatin we have scored the number of sex chromosomes in early spermatids in both irradiated and unirradiated animals. A significant increase in nondisjunction, following treatment, was found with all doses between 25 and 200 R. However, variations in nondisjunction induction at various time intervals following irradiation suggest variations in cell stage sensitivity. More surprising was the large induction of diploid gametes which also demonstrated a significant induction with all irradiation doses. From the distribution of sex chromosomes we conclude that both nondisjunction and diploid gamete induction occur at both meiotic divisions. At present it is not possible to conclude whether the radiation response is linear and to define the cell-stage sensitivity with precision. The reasons for this appear to be variations in sensitivity between animals and also that there is a clear overlap between the duration of the early spermatid stage analyzed (4 days) and the interval between sampling times.