Supernumerary marker chromosome 15 in a male with azoospermia and open bite deformity

Molecular delineation of de novo small supernumerary marker chromosomes in prenatal diagnosis, a retrospective study

OBJECTIVES

To define the genotype-phenotype correlation of small supernumerary marker chromosomes (sSMCs) and conduct precise genetic counseling, we retrospectively searched and reviewed de novo sSMCs cases detected during prenatal diagnosis at The First Affiliated Hospital of Zhengzhou University.

MATERIALS AND METHODS

Chromosome karyotypes of 20,314 cases of amniotic fluid from pregnant women were performed. For 16 samples with de novo sSMCs, 10 were subjected to single-nucleotide polymorphism (SNP) array or low-coverage massively parallel copy number variation sequencing (CNV-seq) analysis.

RESULTS

Among the 10 sSMCs cases, two sSMCs derived from chromosome 9, and three sSMCs derived from chromosomes 12, 18 and 22. The remaining 5 cases were not identified by SNP array or CNV-seq because they lacked euchromatin or had a low proportion of mosaicism. Four of them with a karyotype of 47,XN,+mar presented normal molecular cytogenetic results (seq[hg19] 46,XN), and the remaining patient with a karyotype of 46,XN,+mar presented with Turner syndrome (seq[hg19] 45,X). Five sSMCs samples were mosaics of all 16 cases.

CONCLUSION

Considering the variable origins of sSMCs, further genetic testing of sSMCs should be performed by SNP array or CNV-seq. Detailed molecular characterization would allow precise genetic counseling for prenatal diagnosis.

The effect of chromosome abnormalities on expression of SnoRNA in radioresistant and radiosensitive cell lines after irradiation

In this paper, we have studied the role of chromosomal abnormalities in the expression of small nucleolar RNAs (snoRNAs) of radioresistant (K562) and radiosensitive (HL-60) leukemia cell line. Cells were exposed to an X-ray dose of 4 Gy. SnoRNA expression was investigated using NGS sequencing. The distribution of expressed snoRNAs on chromosomes has been found to be different for two cell lines. The most significant differences in the expression of snoRNAs were found in the K562 cell line based on the analysis of the dynamics of log2fc values. The type of clustering, the number and type of snoRNAs slightly differed in the chromosomes with trisomy and monosomy and had a pronounced difference in pairs with marker chromosomes in both cell lines. In this study, we have demonstrated that chromosomal abnormalities alter the expression of snoRNA after irradiation. Trisomies and monosomies do not have such a noticeable effect on the expression of snoRNAs as the presence of marker chromosomes.

Molecular cytogenetic characterization of small supernumerary marker 15 in infertile male: A case report

Small supernumerary marker chromosomes (sSMCs) are defined as structurally abnormal chromosomes that may be detected pre- or postnataly in patients with developmental and/or mental retardation or infertility. sSMC on chromosome 15 accounts for the highest proportion of all sSMCs and may be detected in subfertile individuals. The present study reports the case of a male patient with oligoasthenoteratozoospermia and an sSMC. The sSMC was identified and characterized according to G-banding analysis, chromosomal microarray analysis (CMA) and fluorescence in situ hybridization (FISH) analysis. Chromosomal karyotype analysis suggested that the patient presented with 47,XY,+mar. CMA was used to characterize the sSMC, which revealed a 0.44-Mb microduplication in 6q25.3q26. Subsequently, FISH using centromere-specific probes for chromosomes 13/21, 14/22 and 15 was applied to identify the origin of the sSMC, which was finally determined to be inverted duplicated(15)(q11.2). It was hypothesized that heterochromatin in the sSMC is responsible for the patient's fertility problem. The presence of heterochromatin may disrupt regular meiosis, thereby affecting normal spermatogenesis. Impaired spermatogenesis in infertile males with an sSMC derived from chromosome 15 was also reviewed by searching published literature and the sSMC database (http://ssmc-tl.com/sSMC.html). For patients with low sperm parameters and complete absence of spermatozoa in the ejaculate, including infertile males with an sSMC with spermatozoa, intracytoplasmic sperm injection is considered as an effective assisted reproductive technique. It may be concluded that molecular cytogenetic techniques are critical tools for delineating sSMCs in infertile males and may be beneficial in identifying sSMC carriers to ensure they receive clinical genetic counseling.

Molecular Characterization of Mosaicism for a Small Supernumerary Marker Chromosome Derived from Chromosome Y in an Infertile Male with Apparently Normal Phenotype: A Case Report and Literature Review

Small supernumerary marker chromosomes (sSMCs), equal in size or smaller than chromosome 20 of the same metaphase, can hardly be identified through traditional banding technique. They are usually associated with intelligent disability, growth retardation, and infertility, but the genotype-phenotype correlations are still complicated for their complex origins and constitutions. Herein, we identified a 26-year-old Chinese infertile male who carried a mosaic sSMC and was diagnosed as severe oligospermia. The G-banding analysis initially described his karyotype as mos 47, XY, +mar[32]/46, XY[18]. The chromosomal microarray analysis results showed a 25.5 Mb gain in Yp11.31q11.23 and a 0.15 Mb loss in Yq12. Two SRY signals were discovered in the “seemingly” normal chromosome Y in both cell lines using SRY probe: one normal SRY was located on the distal tip of the short arm of chromosome Y while the other SRY was located on the terminal of long arm in the same chromosome Y. The sSMC(Y) was finally identified as der(Y) (pter ⟶ q11.23) (SRY-). To our knowledge, the chromosomal Y anomalies, SRY gene translocated from der(Y) (pter ⟶ q11.23) to qter of normal chromosome Y, were not reported before. Our findings indicated that the mosaic presence of sSMC(Y) may be the main cause of severe oligospermia although no other apparent abnormalities were observed in the proband. Further research on association between sSMC(Y) and spermatogenesis impairment should be investigated. It is recommended measures of traditional and molecular cytogenetic analysis should be taken to determine the origins and constitutions of sSMC so as to offer more appropriate genetic counseling for the infertile sSMC carriers.

Male Infertility Associated with a Supernumerary Marker Chromosome

A marker chromosome (mar) is a structurally abnormal chromosome in which no part can be identified. The significance of a marker varies, depending on the material contained within the marker. Very few reports have been published of marker chromosomes associated with male infertility. Here, we report the case of an infertile man with a rare variant of a marker chromosome of a mos 47,XY,+mar[25]/46,XY[25] karyotype.

Prenatal diagnosis and genetic counseling in a fetus associated with risk of Angelman syndrome with a small supernumerary marker chromosome derived from chromosome 22

BACKGROUND

Angelman syndrome (AS) is a neurodevelopmental disorder. AS patients concomitant with sSMC are rather rare events. It will provide more useful and proper information for genetic counseling to identify the sSMC origin.

CASE PRESENTATION

A 27-year-old woman was referred for genetic counseling and prenatal diagnosis at 26 weeks of gestation due to her elder daughter, diagnosed as Angelman syndrome (AS) with an interstitial deletion in one of the chromosomes 15, carrying a small supernumerary marker chromosome (sSMC). The G-banding results of the woman and her current fetus both were 47,XX,+mar. In this paper, fluorescence in situ hybridization (FISH) results showed that there was no deletion of chromosome 15 in the woman and fetus. We demonstrated that the proband's sSMC was maternally inherited and was an inv dup(22)(q11.1) , and that the deletion in 15q11.2-q13.1 was de novo.

CONCLUSIONS

Taking into account above results and normal phenotypes of the proband's mother, in this case we suggest that the sSMC don't increase the recurrence risk of AS. After prenatal diagnosis, the woman chose to continue the pregnancy, and finally gave birth to a normal female infant.

Genetic dosage and position effect of small supernumerary marker chromosome (sSMC) in human sperm nuclei in infertile male patient

Chromosomes occupy specific distinct areas in the nucleus of the sperm cell that may be altered in males with disrupted spermatogenesis. Here, we present alterations in the positioning of the human chromosomes 15, 18, X and Y between spermatozoa with the small supernumerary marker chromosome (sSMC; sSMC⁺) and spermatozoa with normal chromosome complement (sSMC⁻), for the first time described in the same ejaculate of an infertile, phenotypically normal male patient. Using classical and confocal fluorescent microscopy, the nuclear colocalization of chromosomes 15 and sSMC was analyzed. The molecular cytogenetic characteristics of sSMC delineated the karyotype as 47,XY,+der(15)(pter->p11.2::q11.1->q11.2::p11.2->pter)mat. Analysis of meiotic segregation showed a 1:1 ratio of sSMC⁺ to sSMC⁻ spermatozoa, while evaluation of sperm aneuploidy status indicated an increased level of chromosome 13, 18, 21 and 22 disomy, up to 7 × (2.7 − 15.1). Sperm chromatin integrity assessment did not reveal any increase in deprotamination in the patient’s sperm chromatin. Importantly, we found significant repositioning of chromosomes X and Y towards the nuclear periphery, where both chromosomes were localized in close proximity to the sSMC. This suggests the possible influence of sSMC/XY colocalization on meiotic chromosome division, resulting in abnormal chromosome segregation, and leading to male infertility in the patient.

Small Supernumerary Marker Chromosomes in Human Infertility

Small supernumerary marker chromosomes (sSMC) are structurally abnormal chromosomes that cannot be unambiguously identified by banding cytogenetics. The objective of this study was to provide an overview of sSMC frequency and characterization in a context of infertility and to review the literature describing sSMC in relation with male and female infertility. Therefore, a systematic literature review on sSMC associated with infertility was conducted by means of a PubMed literature and a sSMC database (http://ssmc-tl.com/sSMC.html) search. A total of 234 patients with infertility were identified as carriers of sSMC. All chromosomes, except chromosomes 10, 19 and the X, were involved in sSMC, and in 72% the sSMC originated from acrocentric chromosomes. Euchromatic imbalances were caused by the presence of sSMC in 30% of the cases. Putative genes have been identified in only 1.2% of sSMC associated with infertility. The implication of sSMC in infertility could be due to a partial trisomy of some genes but also to mechanical effects perturbing meiosis. Further precise molecular and interphase-architecture studies on sSMC are needed in the future to characterize the relationship between this chromosomal anomaly and human infertility.

Decreased XY recombination and disturbed meiotic prophase I progression in an infertile 48, XYY, +sSMC man

Small supernumerary marker chromosomes (sSMCs) are structurally abnormal rare chromosomes, difficult to characterize by karyotyping, and have been associated with minor dysmorphic features, azoospermia, and recurrent miscarriages. However, sSMC with a gonosomal trisomy has never been reported. Spermatocyte spreading and immunostaining were applied to detect meiotic prophase I progression, homologous chromosome pairing, synapsis, and recombination. In all the analyzed spermatocytes of the patient, the extra Y chromosome was not detected while the sSMC was present. The recombination frequency on autosomes was not affected, while the recombination frequencies on XY chromosome was significantly lower in the patient than in the controls. The meiotic prophase I progression was disturbed with significantly increased proportion of zygotene and decreased pachytene spermatocytes in the patients as compared with the controls. These findings highlight the importance of studies on meiotic behaviors in patients with an abnormal chromosomal constitution and provide an important framework for future studies, which may elucidate the impairment caused by sSMC in mammalian meiosis and fertility.

Array comparative genomic hybridization analysis of small supernumerary marker chromosomes in human infertility

Small supernumerary marker chromosomes (sSMC) are structurally abnormal chromosomes that cannot be unambiguously identified by conventional banding cytogenetics. This study describes four patients with sSMC in relation with infertility. Patient 1 had primary infertility. His brother, fertile, carried the same sSMC (patient 2). Patient 3 presented polycystic ovary syndrome and patient 4 primary ovarian insufficiency. Cytogenetic studies, array comparative genomic hybridization (CGH) and sperm analyses were compared with cases previously reported. sSMC corresponded to the 15q11.2 region (patients 1 and 2), the centromeric chromosome 15 region (patient 3) and the 21p11.2 region (patient 4). Array CGH showed 3.6-Mb gain for patients 1 and 2 and 0.266-Mb gain for patient 4. Sperm fluorescent in-situ hybridization analyses found ratios of 0.37 and 0.30 of sperm nuclei with sSMC(15) for patients 1 and 2, respectively (P < 0.001). An increase of sperm nuclei with disomy X, Y and 18 was noted for patient 1 compared with control and patient 2 (P < 0.001). Among the genes mapped in the unbalanced chromosomal regions, POTE B and BAGE are related to the testis and ovary, respectively. The implication of sSMC in infertility could be due to duplication, but also to mechanical effects perturbing meiosis.