Evaluation of the role of mitotic instability in karyotypically normal men with oligozoospermia

X chromosome-linked genes in the mature sperm influence semen quality and fertility of breeding bulls

The role of sperm expressed X-linked genes on bull fertility has not been studied in detail. The objective of the present study was to assess the influence of X-linked genes on the sperm functional parameters and field fertility rate in the Holstein Friesian cattle (n = 12) and Murrah buffalo (n = 7) bulls. The enrichment analysis (cattle = 8; buffalo = 8) of the X-linked genes was carried out using retrospective RNA-seq data and mRNA expression levels of functionally relevant genes were validated using the RT-qPCR. The mRNA expression levels of these genes were functionally associated with sperm attributes and field fertility rate. The sperm transcriptome studies revealed that the total number of expressed genes and the transcript content of the X-linked genes in the mature sperm were very low in both species, and only 23.31% of these genes were commonly expressed between them. The transcript pool corresponding to the X-linked genes represents embryonic organ development (p = 0.03) and reproduction (p = 0.02) processes in cattle and buffalo sperm, respectively. The mRNA expression levels of X-linked genes, RPL10 and ZCCHC13 in cattle; AKAP4, TSPAN6, RPL10 and RPS4X in buffalo were significantly (p < 0.05) correlated with sperm kinematics. Importantly, the mRNA expression levels of the genes RPL10 (r = -0.68) and RPS4X (r = 0.81) had a significant correlation with the field fertility rate in cattle and buffalo, respectively. Multivariate regression models and receiver operating curve analysis suggest that the mRNA expression levels of X-linked genes may be useful in predicting bull fertility. The study indicates that sperm-expressed X-linked genes influence semen quality and field fertility rate in both cattle and buffalo.

Human Chromosome Y and Haplogroups; introducing YDHS Database

BACKGROUND

As the high throughput sequencing efforts generate more biological information, scientists from different disciplines are interpreting the polymorphisms that make us unique. In addition, there is an increasing trend in general public to research their own genealogy, find distant relatives and to know more about their biological background. Commercial vendors are providing analyses of mitochondrial and Y-chromosomal markers for such purposes. Clearly, an easy-to-use free interface to the existing data on the identified variants would be in the interest of general public and professionals less familiar with the field. Here we introduce a novel metadatabase YDHS that aims to provide such an interface for Y-chromosomal DNA (Y-DNA) haplogroups and sequence variants.

METHODS

The database uses ISOGG Y-DNA tree as the source of mutations and haplogroups and by using genomic positions of the mutations the database links them to genes and other biological entities. YDHS contains analysis tools for deeper Y-SNP analysis.

RESULTS

YDHS addresses the shortage of Y-DNA related databases. We have tested our database using a set of different cases from literature ranging from infertility to autism. The database is at http://www.semanticgen.net/ydhs

CONCLUSIONS

Y-chromosomal DNA (Y-DNA) haplogroups and sequence variants have not been in the scientific limelight, excluding certain specialized fields like forensics, mainly because there is not much freely available information or it is scattered in different sources. However, as we have demonstrated Y-SNPs do play a role in various cases on the haplogroup level and it is possible to create a free Y-DNA dedicated bioinformatics resource.

Cytogenetic and molecular analyses of de novo translocation dic(9;13)(p11.2;p12) in an infertile male

BACKGROUND

Whole arm t(9;13)(p11;p12) translocations are rare and have been described only a few times; all of the previously reported cases were familial.

RESULTS

We present here an infertile male carrier with a whole-arm reciprocal translocation dic(9;13)(p11.2;p12) revealed by GTG-, C-, and NOR-banding karyotypes with no mature sperm cells in his ejaculate. FISH and genome-wide 400 K CGH microarray (Agilent) analyses demonstrated a balanced chromosome complement and further characterised the abnormality as a dicentric chromosome (9;13): dic(9;13)(pter→p11.2::p12→qter),neo(9)(pter→p12→neo→p11.2). An analysis of the patient's ejaculated cells identified immature germ cells at different phases of spermatogenesis but no mature spermatozoa. Most (82.5%) of the germ cells were recognised as spermatocytes at stage I, and the cell nuclei were most frequently found in pachytene I (41.8%). We have also undertaken FISH analysis and documented an increased rate of aneuploidy of chromosomes 15, 18, X and Y in the peripheral blood leukocytes of our patient. To study the aneuploidy risk in leukocytes, we have additionally included 9 patients with non-obstructive azoospermia with normal karyotypes.

CONCLUSIONS

We propose that the azoospermia observed in the patient with the dic(9;13)(p11.2;p12) translocation was most likely a consequence of a very high proportion (90%) of association between XY bivalents and quadrivalent formations in prophase I.

Comparison of aneuploidies of chromosomes 21, X, and Y in the blood lymphocytes and sperm of workers exposed to benzene

Benzene is a primary industrial chemical and a ubiquitous environmental pollutant that causes human leukemia and maybe other malignancies. Occupational exposure to benzene has been associated with increased chromosomal aneuploidies in blood lymphocytes and, in separate studies, in sperm. However, aneuploidy detection in somatic and germ cells within the same benzene-exposed individuals has never been reported. To compare aneuploidies in blood lymphocytes and sperm within the same individuals exposed to benzene, a cross-sectional study was conducted in 33 benzene-exposed male workers and 33 unexposed workers from Chinese factories. Air benzene concentrations in the exposed workers ranged from below the detection limit to 24 ppm (median, 2.9 ppm) and were undetectable in the unexposed subjects. Aneuploidies of chromosomes 21, X, and Y in blood lymphocytes were examined by multicolor fluorescence in situ hybridization and were compared to the previously reported aneuploidies in sperm. The results showed that benzene exposure was positively associated with the gain of chromosome 21 but not sex chromosomes in blood lymphocytes. This was in contrast to analysis of sperm, where the gain of sex chromosomes, but not chromosome 21, was significantly increased in the exposed workers. Furthermore, a significant correlation in the gain of sex chromosomes between blood lymphocytes and sperm was observed among the unexposed subjects, but not among the exposed workers. The findings suggest that benzene exposure induces aneuploidies in both blood cells and sperm within the same individuals, but selectively affects chromosome 21 in blood lymphocytes and the sex chromosomes in sperm.

Genetic reproductive risk in inversion carriers

OBJECTIVE

To evaluate the risk of four inversion carriers for producing unbalanced gametes.

DESIGN

Prospective analysis of sperm nuclei by fluorescence in situ hybridization (FISH).

SETTING

Universitat Autònoma de Barcelona.

PATIENT(S)

Four inversion carriers.

INTERVENTION(S)

A semen sample from each patient was collected and prepared for FISH.

MAIN OUTCOME MEASURE(S)

The segregation outcome of each inversion was analyzed. The presence of interchromosomal effects (ICE) on chromosomes 13, 18, 21, X, and Y was also evaluated.

RESULT(S)

A variable production of unbalanced gametes, which implies a heterogeneous behavior of the inversions, was detected. This variability seems to be directly related to the size of the inversion, indicating that the production of recombinant gametes in inversion carriers would not be relevant when the inverted segment is smaller than 100 Mbp.

CONCLUSION(S)

Inversions have a well-defined reproductive effect on carriers. Carriers of inversions up to 100 Mbp have a low [corrected] reproductive risk and would not usually benefit from preimplantation genetic diagnosis.

Patients with abnormal sperm parameters have an increased sex chromosome aneuploidy rate in peripheral leukocytes

BACKGROUND

Patients with oligoasthenoteratozoospermia (OAT) and normal karyotypes have an increased sperm aneuploidy rate. This may be due to an altered intratesticular environment that affects the chromosomal segregation mechanism(s). Alternatively, it may be due to a generalized meiotic and mitotic abnormality. In this case, patients with abnormal spermatogenesis should also have an increased somatic cell aneuploidy rate. To test this hypothesis, we evaluated peripheral leukocyte aneuploidy rate in patients with spermatogenic impairment.

METHODS

In all, 38 patients were enrolled, of whom 20 had OAT, 15 non-obstructive azoospermia and three Y chromosome (Yq) microdeletions (AZF). Eight healthy normozoospermic men with proven fertility were recruited as controls. Conventional karyotype analysis, AZF microdeletion evaluation and triple-colour FISH for chromosomes X, Y and 12 were conducted in all patients and controls. A total of 1000 lymphocytes were scored for each patient and control.

RESULTS

All patients and controls had a normal karyotype. Sex chromosome aneuploidy rates in peripheral lymphocytes was significantly higher in patients with OAT (0.74+/-0.09%), azoospermia (1.15+/-0.15%) or Yq microdeleted (1.54+/-0.40%), compared with controls (0.15+/-0.03%) (P <0.05).

CONCLUSIONS

Patients with OAT, azoospermia or Yq microdeletions had a slight, but significant, increase of sex chromosome aneuploidy rate in lymphocytes, suggesting the presence of a generalized defective cell division mechanism. In contrast with recent observations, Yq microdeletions do not seem to predispose to a higher number of malsegregation events in somatic cells compared with patients with azoospermia.

Mosaic status in lymphocytes of infertile men with or without Klinefelter syndrome

BACKGROUND

Gonosomal aneuploidies such as Klinefelter syndrome (47,XXY) are the most frequent chromosomal aberration in infertile men. Normally the chromosomal status of patients is detected by karyotyping of up to 20 metaphase spreads of lymphocyte nuclei, whereby low grade mosaicism may be overlooked. To test whether Klinefelter patients with 47,XXY karyotype or infertile men with 46,XY karyotype represent gonosomal mosaicisms, we performed meta- and interphase fluorescence in situ hybridization (FISH) on 45 men.

METHODS AND RESULTS

A total of 400 interphase and 40 metaphase lymphocyte nuclei per patient were scored after hybridization with DNA probes specific for chromosomes X and Y, and chromosome 9 as a control. On the basis of conventional karyotype, hormone levels and clinical appearance, patients were subdivided into 18 Klinefelter syndrome patients with 47,XXY (group I), 11 Klinefelter syndrome-like patients with normal karyotype, 46,XY (group II) and six non-Klinefelter-like infertile patients with normal 46,XY karyotype (group III). Ten normal men (group IV) served as controls. Testicular volume in the Klinefelter group I was smaller compared with group II (P = 0.016), group III (P < 0.001) and group IV (P < 0.001). In addition, testicular volumes in group II were lower compared with group III and group IV (P < 0.004). No significant differences between the aneuploidy rate analysed by FISH in interphase nuclei and metaphases were found in either single patients or groups. Patients with Klinefelter syndrome, 47,XXY (group I) or with symptoms similar to those in Klinefelter patients 46,XY (group II) showed a similar aneuploidy rate (group I 7.1 +/- 4.0% and group II 4.6 +/- 3.4%) and two 47,XXY patients with a high prevalence for normal 46,XY lymphocytes had sperm in their ejaculate. However, in general, no correlations between FISH mosaic status and serum hormone parameters, nor with ejaculate parameters were found.

CONCLUSIONS

The results suggest that 47,XXY patients with an increased incidence of XY cells (average of 4.2 +/- 2.3) may have a higher probability of germ cells as we found sperm only in the ejaculate of Klinefelter syndrome patients with mosaic 46,XY cells (6.0 and 7.0%). On the other hand, 46,XY patients with mosaic sex chromosome aneuploidies detected by FISH analysis more often show symptoms of hypogonadism phenotypically resembling Klinefelter syndrome.

Cytogenetic studies in patients with reproductive failure

BACKGROUND

Cytogenetic studies in patients with reproductive failure

AIM

To investigate the contribution of chromosomal abnormalities in sub fertility and in couples with repeated abortions.

METHODS

Hundred and 13 couples who had at least two or more spontaneous abortions and 65 women and 63 men with infertility were analyzed cytogenetically.

RESULTS

Major chromosomal rearrangements were found in 8% and minor variants in 6% in the study population. Major chromosomal aberrations were judged to explain 4.9% of recurrent abortions and 13% of infertility. Chromosomal abnormalities in infertile men occurred in 5% and in infertile women in 21.5%. The chromosomal abnormalities were structural (57%), numerical (18%) or mosaics (25%).

CONCLUSIONS

Chromosomal aberrations in recurrent abortions are mostly structural ones and those in female infertility mosaicism of sex chromosomes. Turner's syndrome, Turner variants and XY females are detected as a cause of female infertility. The structural and numerical aberrations of either sex or autosomal chromosomes were found in infertile men.

Stable variants of sperm aneuploidy among healthy men show associations between germinal and somatic aneuploidy

Repeated semen specimens from healthy men were analyzed by sperm fluorescence in situ hybridization (FISH), to identify men who consistently produced elevated frequencies of aneuploid sperm and to determine whether men who were identified as stable variants of sperm aneuploidy also exhibited higher frequencies of aneuploidy in their peripheral blood lymphocytes. Seven semen specimens were provided by each of 15 men over a 2-year period and were evaluated by the X-Y-8 multicolor sperm FISH method (i.e., approximately 1,050,000 sperm were analyzed from 105 specimens). Three men were identified as stable aneuploidy variants producing significantly higher frequencies of XY, disomy X, disomy Y, disomy 8, and/or diploid sperm over time. In addition, one man and three men were identified as sperm-morphology and sperm-motility variants, respectively. Strong correlations were found between the frequencies of sperm with autosomal and sex-chromosome aneuploidies and between the two types of meiosis II diploidy; but not between sperm aneuploidy and semen quality. A significant association was found between the frequencies of sex-chromosome aneuploidies in sperm and lymphocytes in a subset of 10 men (r2=0.67, P=.004), especially between XY sperm and sex-chromosome aneuploidy in lymphocytes (r2=0.70, P=.003). These findings suggest that certain apparently healthy men can produce significantly higher frequencies of both aneuploid sperm and lymphocytes. Serious long-term somatic and reproductive health consequences may include increased risks of aneuploidy-related somatic diseases and of having children with paternally transmitted aneuploidies, such as Klinefelter, Turner, triple-X, and XYY syndromes.

Genetically determined male infertility and assisted reproduction techniques

This is a review of the common chromosome and genetic disorders associated with male infertility that need to be considered by the clinician and the couple in the context of treatment. Until recently the most relevant disorders have been those inherited from parents, however, with the advent of technologies enabling recovery of sperm from the testicle in men with severely damaged spermatogenesis there is increased interest in those genetic abnormalities that may occur in mitosis and meioses. It is likely that over the next ten years there will be increasing focus on this aspect of male fertility genetic disorders. This article needs to be read in conjunction with the specific in depth reviews in this journal edition.

Role of mitotic control in spermatogenesis

OBJECTIVE

To study the correlation between the incidence of sex chromosome aneuploidies in the somatic cells and spermatozoa in karyotypically normal infertile men and fertile donors.

DESIGN

A prospective, phase two, controlled study.

SETTING

A teaching Hospital Reproductive Medicine and Medical Genetics Units.

PATIENT(S)

Ten patients with idiopathic oligozoospermia and 10 sperm donors with proven fertility, all with a normal karyotype 46, XY.

INTERVENTION(S)

Multicolor fluorescence in situ hybridization (FISH) of peripheral blood lymphocytes and spermatozoa using a probe cocktail containing the alpha satellite DXZ1 for the X centromere, DYZ1 for the heterochromatic region of the long arm of the Y, and cosmids D21S259, D21S341, and D21S342 for Down syndrome critical region of chromosome 21.

MAIN OUTCOME MEASURE(S)

The incidence of chromosome X, Y, and 21 aneuploidies in peripheral lymphocytes and spermatozoa in both groups.

RESULT(S)

The incidence of aneuploidies related to chromosomes X, Y, and 21 were significantly higher in peripheral lymphocytes and spermatozoa of infertile men compared with donors. There was a positive correlation between the incidence of chromosome aneuploidies in the somatic cells and sperm in all men.

CONCLUSION(S)

These findings provide suggestive evidence for the importance of mitosis in spermatogenesis and the role of mitotic instability in unexplained oligozoospermia.

Genetics and male infertility

This article reviews chromosomal and genetic disorders in the context of male fertility. Particular emphasis is on those disorders, which are encountered, in clinical practice including Klinefelter's syndrome, Kallman's syndrome, Androgen insensitivity, Y microdeletions, Y fertility gene deletions, and cystic fibrosis gene mutations. These disorders are discussed in relation to the aetiology of male fertility and also risks to children who are born of fathers with these disorders. A list of fathers' categories is proposed for outcome studies for children born after IVF-ICSI. Finally a question is proposed to catalyse debate about germ line therapy.