Chromosome aneuploidy in the spermatozoa of two men with globozoospermia

Globozoospermia: A Case Report and Systematic Review of Literature

PURPOSE

Globozoospermia is a genetic syndrome characterized by the presence of round-headed spermatozoa and infertility due to the inability of these spermatozoa to fertilize the oocyte. In this article, we present the clinical case of a young globozoospermic patient with a new, not yet described mutation of the DPY19L2 gene. We also performed a systematic review of the literature on gene mutations, the outcome of assisted reproductive techniques, and the risk of transmission of abnormalities to the offspring in patients with globozoospermia and made recommendations to offer a more appropriate clinical management of these patients.

MATERIALS AND METHODS

We performed a systematic search in the PubMed, Google Scholar, and Scopus databases from their inception to December 2021. The search strategy included the combination of the following Medical Subjects Headings (MeSH) terms and keywords: "globozoospermia", "round-headed spermatozoa", "round head spermatozoa", "intracytoplasmic sperm injection", "ICSI", "offspring", "child health", "assisted reproductive technique outcome". All the eligible studies were selected following the PECOS (Population, Exposure, Comparison/Comparator, Outcomes, Study design) model. The quality of included studies was assessed by applying the "Cambridge Quality Checklists".

RESULTS

The main genes involved in the pathogenesis of globozoospermia are DPY19L2, SPATA16, PICK1, GGN, SPACA1, ZPBP, CCDC62, and CCNB3 genes. Other genes could also play a role. These include C2CD6, C7orf61, CCIN, DNH17, DNH6, PIWIL4, and CHPT1. Globozoospermic patients should undergo ART to achieve fertility. In particular, intracytoplasmic sperm injection with assisted oocyte activation or intracytoplasmic morphologically-selected sperm injection appears to be associated with a higher success rate. Patients with globozoospermia should also be evaluated for the high rate of sperm aneuploidy which appears to influence the success rate of ART but does not appear to be associated with an increased risk of transmission of genetic abnormalities to offspring.

CONCLUSIONS

This systematic review summarizes the evidence on the gene panel to be evaluated, ICSI outcomes, and the health of the offspring in patients with globozoospermia. Evidence-based recommendations on the management of patients with globozoospermia are provided.

Increased chromosome 16 disomy rates in human spermatozoa and recurrent spontaneous abortions

OBJECTIVE

To investigate if unexplained recurrent spontaneous abortions (RSA) are associated with increased rates of aneuploidy in spermatozoa of RSA partners ("RSA-men").

DESIGN

Case-control study.

SETTING

Academic research center.

PATIENT(S)

Patients enrolled at the Hormone and Fertility Center and controls at the Department of Urology (LMU-Munich).

INTERVENTION(S)

Sperm samples of 11 partners of unexplained RSA cases evaluated for elevated diploidy and disomy levels of chromosomes 1-22, X, and Y by multicolor sperm fluorescence in situ hybridization (FISH).

MAIN OUTCOME MEASURE(S)

Aneuploidy rates obtained in RSA-men compared with controls from the literature and internally; an increase of the aneuploidy rate was considered statistically significant, when it differed ≥ 2 standard deviations from the mean baseline level in controls.

RESULT(S)

Our sperm FISH data on RSA men showed increased disomy rates for at least three chromosomes in more than 60% of patients but no statistically significant increase of the overall mean sperm disomy or diploidy rate. In particular, meiotic errors involving chromosome 16 contributed to increased sperm disomy in more than 60% of our patients.

CONCLUSION(S)

These data suggest that among paternal meiotic errors nondisjunction of chromosome 16 might have similar relative influence on fetal aneuploidy compared with maternal chromosome 16 disomy.

Genetic aspects of monomorphic teratozoospermia: a review

Teratozoospermia is characterized by the presence of spermatozoa with abnormal morphology over 85 % in sperm. When all the spermatozoa display a unique abnormality, teratozoospermia is said to be monomorphic. Two forms of monomorphic teratozoospermia, representing less than 1 % of male infertility, are recognized: macrozoospermia (also called macrocephalic sperm head syndrome) and globozoospermia (also called round-headed sperm syndrome). Macrozoospermia is defined as the presence of a very high percentage of spermatozoa with enlarged head and multiple flagella. Meiotic segregation studies in 30 males revealed that over 90 % of spermatozoa were aneuploid, mainly diploid. Sperm DNA fragmentation studies performed in a few patients showed an increase in DNA fragmentation index compared to fertile men. Four mutations in the AURKC gene, a key player in meiosis and more particularly in spermatogenesis, have been found to be responsible for macrozoospermia. Globozoospermia is characterized by round-headed spermatozoa with an absent acrosome, an aberrant nuclear membrane and midpiece defects. The rate of aneuploidy of various chromosomes in spermatozoa from 26 globozoospermic men was slightly increased compared to fertile men. However, this increase was of the same order as that commonly found in infertile men with altered sperm parameters. The majority of the studies found that globozoospermic males had a sperm DNA fragmentation index higher than in fertile men. Mutations or deletions in three genes, SPATA16, PICK1 and DPY19L2, have been shown to be responsible for globozoospermia. Identification of the genetic causes of macrozoospermia and globozoospermia should help refine diagnosis and treatment of these patients, avoiding long and painful treatments. Elucidating the molecular causes of these defects is of utmost importance as intracytoplasmic sperm injection (ICSI) is very disappointing in these two pathologies.

Sperm aneuploidy in infertile male patients: a systematic review of the literature

Males with abnormal karyotypes and subgroups of fertile and infertile males with normal karyotypes may be at risk of producing unbalanced or aneuploid spermatozoa. Biological, clinical, environmental and other factors may also cause additional sperm aneuploidy. However, increased risk of sperm aneuploidy is directly related to chromosomally abnormal embryo production and hence to poor reproductive potential. This systemic literature review focuses on the identification of these males because this is an essential step in the context of assisted reproduction. This research may allow for a more personalised and, hence, more accurate estimation of the risk involved in each case, which in turn will aid genetic counselling for affected couples and help with informed decision-making.

Successful delivery following intracytoplasmic sperm injection with calcium ionophore A23187 oocyte activation in a partially globozoospermic patient

PURPOSE

To describe a successful pregnancy outcome following intracytoplasmic sperm injection (ICSI) with assisted oocyte activation (AOA) in a case of partial globozoospermia.

METHODS

AOA was accomplished with calcium ionophore A23187. Sperm morphology was observed via light, fluorescent and electron microscopy following a Diff-Quik stain and fluorescein isothiocyanate-labeled peanut agglutinin (FITC-PNA) staining. An activation ability test was employed using a mouse oocyte exposed to strontium chloride.

RESULTS

Via light microscopy, it was found that a large number of sperm possessed deficient acrosomes and a sharply rounded head; however, we observed both normal and the aforementioned abnormal sperm via FITC-PNA staining of a semen specimen. Mouse oocyte activation was 87.5 % via natural activation without AOA. With AOA after ICSI, 100 % oocyte activation was observed. Five oocytes were retrieved, and AOA with A23187 after ICSI resulted in a high fertilization rate (4 of 5, 80 %). Two embryos developed and the patient subsequently delivered a healthy female infant without any congenital abnormalities.

CONCLUSIONS

We report a successful pregnancy outcome using an early stage embryo, which developed following ICSI using sperm from a partially globozoospermic patient who possessed temporary potential oocyte activation.

The use of fluorescent in situ hybridization in male infertility

Male factors are implicated in up to 50% of couples being evaluated and treated for infertility with advanced assisted reproductive technologies. Genetic abnormalities, including sperm chromosome aneuploidy as well as structural aberrations, are one of the major causes of infertility. The use of chromosome-specific DNA probes labeled with fluorochromes, particularly the combination with multiple probes, has been used to indirectly study the sperm chromosome by fluorescent in situ hybridization (FISH). Clinically, this technique is also used to assess the sperm of men recovering from gonadotoxic treatment. Recent advances in this technology facilitate the evaluation of sperm aneuploidy. Sperm FISH is a widely used screening tool to aid in counseling couples with severe male factor infertility, especially in cases of prior repeated in vitro fertilization/intracytoplasmic sperm injection failure or recurrent pregnancy loss. Automation of FISH imaging and analysis, as well as the development of emerging techniques such as comparative genomic hybridization, will all contribute to the promise of future diagnostic approaches aimed at improving the quality, ease, and efficiency of aneuploidy analysis.

A recurrent deletion of DPY19L2 causes infertility in man by blocking sperm head elongation and acrosome formation

An increasing number of couples require medical assistance to achieve a pregnancy, and more than 2% of the births in Western countries now result from assisted reproductive technologies. To identify genetic variants responsible for male infertility, we performed a whole-genome SNP scan on patients presenting with total globozoospermia, a primary infertility phenotype characterized by the presence of 100% round acrosomeless spermatozoa in the ejaculate. This strategy allowed us to identify in most patients (15/20) a 200 kb homozygous deletion encompassing only DPY19L2, which is highly expressed in the testis. Although there was no known function for DPY19L2 in humans, previous work indicated that its ortholog in C. elegans is involved in cell polarity. In man, the DPY19L2 region has been described as a copy-number variant (CNV) found to be duplicated and heterozygously deleted in healthy individuals. We show here that the breakpoints of the deletions are located on a highly homologous 28 kb low copy repeat (LCR) sequence present on each side of DPY19L2, indicating that the identified deletions were probably produced by nonallelic homologous recombination (NAHR) between these two regions. We demonstrate that patients with globozoospermia have a homozygous deletion of DPY19L2, thus indicating that DPY19L2 is necessary in men for sperm head elongation and acrosome formation. A molecular diagnosis can now be proposed to affected men; the presence of the deletion confirms the diagnosis of globozoospermia and assigns a poor prognosis for the success of in vitro fertilization.

Fertilisation failure after intracytoplasmic sperm injection is not associated with sperm aneuploidy of a globozoospermic patient

The objective of this study was to determine the aneuploidy rate in spermatozoa from a globozoospermic patient who underwent three unsuccessful intracytoplasmic sperm injection (ICSI) treatment cycles together with his wife. The aneuploidy rates of chromosomes 13, 18, 21, X and Y as well as the diploidy rate in the spermatozoa of this man were evaluated by fluorescence in situ hybridisation to clarify if chromosomal aneuploidy could be a cause for the low fertilisation rate observed in this case. In the spermatozoa of our patient no increase in aneuploidy rates was found for the tested chromosomes (0.0% disomies of chromosomes 13, 18 and 21 with a diploidy rate of 0.6%; X/Y missegregation: 0.6%) indicating that the ICSI outcome of the couple was not impaired by sperm aneuploidy of the globozoospermic man.

Ultrastructural nuclear defects and increased chromosome aneuploidies in spermatozoa with elongated heads

BACKGROUND

Cellular and molecular mechanisms leading to elongated sperm heads are not known. We have analysed the nuclear status of spermatozoa with elongated heads.

METHODS

Fourteen men with at least 30% of spermatozoa with an elongated nucleus were studied and compared with five fertile men as controls. Sperm morphology was analysed by a quantitative ultrastructural analysis. Sperm chromosomal content was assessed by three-colour fluorescence in-situ hybridization (chromosomes X, Y, 18). Y chromosome microdeletion and karyotype were analysed.

RESULTS

Elongated sperm head rates of the patients were 46.9% (30-75 versus 0-2% in the control group) by light microscopy and 34.4% by electron microscopy. In all patients, the chromatin was poorly condensed in elongated sperm heads (50% of elongated nuclei). No anomalies of sperm biochemical markers were found. All the men showed normal karyotype (46,XY) and absence of Y chromosome microdeletion. Aneuploidy rates of gonosomes and chromosome 18 were significantly increased in patients (1.64- and 3.6-fold, P = 0.006 and 0.026, respectively).

CONCLUSIONS

This study demonstrates that impaired chromatin compaction and slightly increased chromosome aneuploidies are found in spermatozoa with an elongated head, suggesting possible mechanisms such as meiotic non-disjunctions or spermiogenesis anomalies.

Sperm morphology and aneuploidies: defects of supposed genetic origin

As individuals with genetic sperm defects are intracytoplasmic sperm injection candidates, the study of the chromosomal constitution of their spermatozoa is of great interest. This study is a review of the current literature concerning fluorescence in situ hybridisation studies in spermatozoa with genetic sperm defect as 'round head', 'dysplasia of fibrous sheath' (DFS), 'primary ciliary dyskinesia' (PCD), the 'detached tail' and the 'absence of fibrous sheath'. Regarding sperm head defects, elevated XY disomy and diplodies were detected. Genetic defects affecting the sperm tail seemed to have a different correlation with chromosome meiotic segregation. Only chromosome 18, among the autosomes, was studied and the percentage of frequency of disomy was generally within the normal range. In the more frequently studied defect, DFS, the alterations in gonosome disomy and diploidy were recorded by different groups. Regarding PCD defects, elevated frequencies of disomy of sex chromosomes and diploidy were observed, whereas the absence of the fibrous sheath and the detached tail did not show any meiotic disturbance. The problem of genetic sperm defects should be seriously considered when these sperm are used for assisted reproduction, owing to the high risk of transmission of chromosomal imbalance and of mutations that could cause genetic sperm defects in offspring.

Globozoospermia revisited

Globozoospermia is a rare (incidence <0.1%) but severe disorder in male infertility. Total globozoospermia is diagnosed by the presence of 100% round-headed spermatozoa lacking an acrosome. It is still unclear whether patients whose ejaculate contains both normal and globozoospermic cells (partial globozoospermia) suffer from a variation of the same syndrome. Apart from the fact that affected males suffer from reduced fertility or even infertility, no other physical characteristics can be associated with the syndrome. ICSI is a treatment option for these patients, although low fertilization rates after ICSI show a reduced ability to activate the oocyte. In globozoospermic cells, the use of acrosome markers has demonstrated an absent or severely malformed acrosome. Chromatin compaction appears to be disturbed but is not consistently over- or undercondensed. In some cases, an increased number of cells with DNA fragmentation have been observed. The analysis of the cytogenetic composition revealed an increased aneuploidy rate in some cases. Nonetheless, no increased number of spontaneous abortions or congenital defects has been reported in pregnancies conceived after ICSI. The pathogenesis of globozoospermia most probably originates in spermiogenesis, more specifically in acrosome formation and sperm head elongation. In several knockout mouse models, a phenotype similar to that in humans was found. Together with the occurrence of affected siblings, these findings indicate a genetic origin, which makes globozoospermia a good candidate for genetic analysis. More research is needed to elucidate the pathogenesis of human globozoospermia to further understand globozoospermia as well as (abnormalities in) spermiogenesis and spermatogenesis in general.

Is there a relationship between sperm chromosome abnormalities and sperm morphology?

This review explores the relationship between sperm chromosomal constitution and morphology. With the advent of techniques for obtaining information on the chromosome complements of spermatozoa, this relationship has been studied in fertile men and in men with a high frequency of chromosomal abnormalities. Using human sperm karyotype analysis, no relationship between sperm chromosome abnormalities and morphology was found in fertile men, translocation carriers or post-radiotherapy cancer patients. Fluorescence in situ hybridization (FISH) analysis has not generally revealed a specific association between morphologically abnormal sperm and sperm chromosome abnormalities, but has indicated that teratozoospermia, like other forms of abnormal semen profiles (aesthenozoospermia, oligozoospermia) is associated with a modest increase in the frequency of sperm chromosome abnormalities. However, FISH studies on some infertile men and mouse strains have suggested that certain types of morphologically abnormal spermatozoa, such as macrocephalic multitailed spermatozoa, are associated with a very significantly increased frequency of aneuploidy. Thus, there may be an association between sperm morphology and aneuploidy in infertile men with specific abnormalities.

Chromosome abnormalities in sperm from infertile men with normal somatic karyotypes: teratozoospermia

Teratozoospermia is characterized by the presence of spermatozoa with abnormal morphology in sperm. This condition is frequently associated with infertility and intracytoplasmic sperm injection (ICSI) is frequently used as the treatment of choice. However, the use of ICSI has created consequential debate concerning the genetic risk for the offspring. Fluorescence in situ hybridization technique (FISH), allowing the specific identification of human chromosomes in sperm nuclei, has been used to study chromosome abnormalities in sperm from men with teratozoospermia and a normal karyotype. In this review, we present studies that have tried to determine if men with a normal blood karyotype but suffering from teratozoospermia present a higher aneuploidy frequency. The literature is limited to three forms of teratozoospermia. The first group consists of "polymorphic teratozoospermia", where a majority of spermatozoa display more than one type of abnormality. In this case, only a slight increase in aneuploidy frequency is observed, which cannot be differentiated from the results observed in oligo-astheno-teratozoospermia (OAT). The second group, named "globozoospermia", is characterized by round spermatic heads, absence of acrosome and disorganization of mid-piece and tail. In this case, some studies have shown a significant, but moderate, increase in the aneuploidy frequency for acrocentrics and sex chromosomes. The aneuploidy frequency remains low, also ICSI can be proposed to these patients, but few successes occur. The third group consists of "enlarged head teratozoospermia", where almost all spermatozoa have an enlarged head, multiple tail and abnormal acrosome. In this case a very high level of missegregation is observed, leading to nearly 100% aneuploidy. In this particular group, ICSI must be refuted, and patients have to be redirected to other possibilities, like sperm donation.