Diagnostic genetic screening for assisted reproductive technologies patients with macrozoospermia

Successful intracytoplasmic sperm injection in a macrozoospermia case with novel compound heterozygous aurora kinase C (AURKC) mutations

PURPOSE

To explore the application possibility of macrocephalic sperm from a patient with 100% macrocephalic sperm and AURKC gene variations.

METHODS

We diagnosed a case of macrozoospermia with 100% macrocephalic sperm and 39.5% multi-tailed spermatozoa by morphological analysis. Whole-exome sequencing (WES) was used for the patient and his wife. Sanger sequencing technique was used to verify the AURKC mutations in the patient's parents and his offspring. Sperm's ploidy was tested by flow cytometry. The couple asked for intra-couple ART therapy.

RESULTS

The patient presented novel compound heterozygous AURKC mutations (c.434C > T, c.497A > T) by WES. Sanger sequencing validation showed that variant of c.434C > T was observed in his father and c.497A > T was observed in his mother. Flow cytometry revealed that there existed a certain proportion of haploid sperm. Macrocephalic spermatozoa whose heads were smaller than the diameter of injection needle were selected for microinjection. A singleton pregnancy was achieved after embryo transfer. Prenatal diagnosis revealed that the fetus had normal chromosomal karyotype. Sanger sequencing technique showed that the fetus carried a c.434C > T mutation in one AURKC allele. A 3730 g healthy male fetus was delivered at term.

CONCLUSION

Our study reported a successful live birth from a patient with definite AURKC gene variants and may provide insights for such patients to choose donor sperm or their own sperm.

Genetic Causes of Qualitative Sperm Defects: A Narrative Review of Clinical Evidence

Several genes are implicated in spermatogenesis and fertility regulation, and these genes are presently being analysed in clinical practice due to their involvement in male factor infertility (MFI). However, there are still few genetic analyses that are currently recommended for use in clinical practice. In this manuscript, we reviewed the genetic causes of qualitative sperm defects. We distinguished between alterations causing reduced sperm motility (asthenozoospermia) and alterations causing changes in the typical morphology of sperm (teratozoospermia). In detail, the genetic causes of reduced sperm motility may be found in the alteration of genes associated with sperm mitochondrial DNA, mitochondrial proteins, ion transport and channels, and flagellar proteins. On the other hand, the genetic causes of changes in typical sperm morphology are related to conditions with a strong genetic basis, such as macrozoospermia, globozoospermia, and acephalic spermatozoa syndrome. We tried to distinguish alterations approved for routine clinical application from those still unsupported by adequate clinical studies. The most important aspect of the study was related to the correct identification of subjects to be tested and the correct application of genetic tests based on clear clinical data. The correct application of available genetic tests in a scenario where reduced sperm motility and changes in sperm morphology have been observed enables the delivery of a defined diagnosis and plays an important role in clinical decision-making. Finally, clarifying the genetic causes of MFI might, in future, contribute to reducing the proportion of so-called idiopathic MFI, which might indeed be defined as a subtype of MFI whose cause has not yet been revealed.

The identification of AMZ2 as a candidate causative gene in a severe teratozoospermia patient characterized by vacuolated spermatozoa

Teratozoospermia with cephalic defects is one of the most severe types of sperm defects known to date. While several monogenic factors are linked to cephalic abnormalities, such as globozoospermia and macrozoospermia, the genetic cause of vacuolated spermatozoa remains inadequately described. Here, we analyzed whole-exome sequencing (WES) data for an individual from a consanguineous family with severely vacuolated spermatozoa. The analysis revealed a novel homozygous c.520A>G (p.Thr174Ala) variant in the archaelysin family metallopeptidase 2 ( AMZ2 ), a gene that encodes a zinc metalloprotease previously shown to be highly expressed in the testes and sperm. Multiple algorithms predicted this variant to be a damaging mutation. Consistent with an autosomal recessive mode of inheritance, this variant was inherited from heterozygous parental carriers. To investigate the potential pathogenicity of the identified variant, we compared the AMZ2 expression in sperm cells from the patient with the AMZ2 variant and from a healthy control. Immunoblot analysis revealed that the homozygous missense variant in AMZ2 abolished AMZ2 expression in the spermatozoa. Our findings reveal a candidate causative gene for vacuolated spermatozoa.

Sperm morphology: Evaluating its clinical relevance in contemporary fertility practice

Background

The World Health Organization (WHO) recommends reporting sperm morphology in a standard semen analysis. However, the clinical utility and prognostic value of morphology is often debated.

Methods

We reviewed and summarized studies that assessed both the benefits and limitations of sperm morphology in the context of natural fertility, assisted reproductive technologies, and recurrent pregnancy loss. We additionally describe possible environmental and anatomical etiologies of teratozoospermia.

Results

Sperm morphology evaluation has continuously evolved since the release of the first WHO manual in 1980. Initially, several large studies reported significant inverse associations between fertility outcomes and teratozoospermia. Most recent studies, however, fail to show an association between sperm morphology and natural or assisted fertility outcomes.

Conclusion

Sperm morphology analysis may have limited diagnostic and prognostic value. Providers should be aware of these limitations when counseling or managing infertile patients.

The relevance of sperm morphology in male infertility

This brief report concerns the role of human sperm morphology assessment in different fields of male infertility: basic research, genetics, assisted reproduction technologies, oxidative stress. One of the best methods in studying sperm morphology is transmission electron microscopy (TEM) that enables defining the concept of sperm pathology and classifying alterations in non-systematic and systematic. Non-systematic sperm defects affect head and tail in variable ratio, whereas the rare systematic defects are characterized by a particular anomaly that marks most sperm of an ejaculate. TEM analysis and fluorescence in situ hybridization represent outstanding methods in the study of sperm morphology and cytogenetic in patients with altered karyotype characterizing their semen quality before intracytoplasmic sperm injection. In recent years, the genetic investigations on systematic sperm defects, made extraordinary progress identifying candidate genes whose mutations induce morphological sperm anomalies. The question if sperm morphology has an impact on assisted fertilization outcome is debated. Nowadays, oxidative stress represents one of the most important causes of altered sperm morphology and function and can be analyzed from two points of view: 1) spermatozoa with cytoplasmic residue produce reactive oxygen species, 2) the pathologies with inflammatory/oxidative stress background cause morphological alterations. Finally, sperm morphology is also considered an important endpoint in in vitro experiments where toxic substances, drugs, antioxidants are tested. We think that the field of sperm morphology is far from being exhausted and needs other research. This parameter can be still considered a valuable indicator of sperm dysfunction both in basic and clinical research.

Pathogenic variant in ACTL7A causes severe teratozoospermia characterized by bubble-shaped acrosomes and male infertility

Teratozoospermia is a common factor associated with male infertility. However, teratozoospermia characterized by bubble-shaped acrosomes (BSAs) has not yet been identified in men and the causative genes are unknown. The present study is of a patient with severe teratozoospermia characterized by BSA and carrying a variant (c.1204G>A, p. Gly402Ser) of actin-like 7A (ACTL7A). For further verification, we generated an Actl7a-mutated mouse model (p.Gly407Ser) carrying an equivalent variant to that in the patient. We found that homozygous Actl7a-mutated (Actl7aMut/Mut) male mice were sterile, and all their sperm showed acrosomal abnormalities. We detected, by transmission electron microscopy, that during acrosomal biogenesis the acrosome detaches from the nuclear membrane in Actl7aMut/Mut mice. Furthermore, mutant ACTL7A failed to attach to the acroplaxome and was discharged by cytoplasmic droplets, which led to the absence of ACTL7A in epididymal spermatozoa in mice. The mutant sperm failed to activate the oocyte, and sperm-borne oocyte activation factor PLCζ discharge accompanied by ACTL7A was observed, leading to total fertilization failure (TFF). Immunoprecipitation followed by liquid chromatography-mass spectrometry showed that several differentially expressed proteins participate in acrosome assembly and actin filament organization. Furthermore, assisted oocyte activation by calcium ionophore exposure successfully overcame TFF in the couple with an ACTL7A pathogenic variant. Our study defined a novel phenotype of an acrosomal abnormality characterized by BSA, revealed the underlying mechanism of a pathogenic variant in ACTL7A, and provided a genetic marker and potential therapeutic option for male infertility.

Genetics of teratozoospermia: Back to the head

Spermatozoa are polarized cells with a head and a flagellum joined by the connecting piece. Head integrity is critical for normal sperm function, and head defects consistently lead to male infertility. Abnormalities of the sperm head are among the most severe and characteristic sperm defects. Patients presenting with a monomorphic head sperm defects such as globozoospermia or marcrozoospermia were analyzed permitting to identify several key genes for spermatogenesis such as AURKC and DPY19L2. The study of patients with other specific sperm head defects such as acephalic spermatozoa have also enabled the identification of new infertility genes such as SUN5. Here, we review the genetic causes leading to morphological defects of sperm head. Advances in the genetics of male infertility are necessary to improve the management of infertility and will pave the road towards future strategies of treatments, especially for patients with the most severe phenotype as sperm head defects.

Two frequent loss-of-function mutations in Aurora Kinase C gene in Algerian infertile men with macrozoospermia

Macrozoospermia is associated with severe male infertility. To date, the only gene implicated in this phenotype is the Aurora Kinase C gene. We report in this work the genetic screening of AURKC mutations in 34 patients with macrozoospermia among 3,536 Algerian infertile men. Nineteen patients (56%) were homozygotes for the c.144delC mutation, eight (23.52%) homozygotes for the c.744C>G (p.Y248*) mutation and two (5.88%) compound heterozygotes. No AURKC mutation was identified in five patients (14.7%). Interestingly and although it is generally accepted that nearly all positive mutated AURKC patients have close to 100% large-head spermatozoa, our results showed that 11 patients with AURKC mutations (32.35%) had large-headed spermatozoa lower than 70% (7 with c.144delC and 4 with p.Y248*), and no mutation was found in 2 patients who had >70% of macrocephalic spermatozoa. Twenty ICSI attempts were performed before genetic screening resulting in 39 embryos but no pregnancy was obtained. The sequencing of AURKC exons 3 and 6 is appropriate as a first-line genetic exploration in these patients to avoid unsuccessful ICSI attempts. A percentage of large head spermatozoa beyond 25% and a percentage of multiflagellar spermatozoa beyond 10% are predictive of a positive mutation diagnosis.

Compound heterozygosity for novel AURKC mutations in an infertile man with macrozoospermia

Among causes of infertility, teratozoospermia is characterised by a percentage of morphologically abnormal spermatozoa >4%. Macrozoospermia, one form of monomorphic teratozoospermia, is observed in <1% of cases of male infertility and is described as approximately 100% large-headed and/or multitailed spermatozoa. This study reports that an infertile man with large-head spermatozoa presenting compound heterozygosity aurora kinase C (AURKC) mutations (c.382C>T, c.572C>T) by whole-exome sequencing. Consequently, both two novel AURKC mutations had high probability of damage-causing and conserved across species and extremely low allele frequency in the population. Flow cytometry analysis revealed a high ratio of sperm DNA fragmentation. Two intracytoplasmic sperm injection (ICSI) procedures were attempted for the patient, but all were unsuccessful. These results indicate that sequence analysis should be performed for the variants of AURKC in Chinese patients with macrozoospermia.

Mutational analysis of Aurora kinase C gene in Egyptian patients with macrozoospermia

Macrozoospermia is a rare syndrome. The key marker of the disease is a high percentage of spermatozoa with abnormal phenotypes namely enlarged head and multiple tails. The presence of at least 70% of spermatozoa with a large head is usually associated with Aurora kinase C gene (AURKC) mutations. We sought to assess AURKC as a potential genetic actor of macrozoospermia in a sample of infertile Egyptian men. We recruited 30 patients and conducted a clinical examination, semen analysis, and DNA sequencing and RFLP for AURKC. We diagnosed 17 patients with characteristic macrozoospermia and classified them into eight severe and nine mild cases. We detected genetic variants of AURKC in five patients (29.4%): Three patients with severe macrozoospermia had c.144delC mutations in exon 3 (37.5% of the severe), and two mild cases had c.1157G>A polymorphism in the 3' UTR (22.2% of the mild). A successful intracytoplasmic sperm injection (ICSI) was achieved only with a severe macrozoospermia patient without apparent AURKC mutation. The present study is the first report to link macrozoospermia and AURKC mutations in Egypt. The study recommends macrozoospermia patients to perform AURKC gene analysis and attempt ICSI, even those with a high percentage of large head spermatozoa.

Cutting-Edge Evaluation of Male Infertility

A male factor is a contributor in 50% of cases of infertility. Although assisted reproductive techniques can often bypass the need to improve semen parameters, the evaluation of the infertile man remains critical. Current methods for evaluating the infertile man are discussed, beginning with the basic workup that all suspected infertile men should undergo, followed by subsequent evaluation steps. Although the fundamental components of the evaluation have remained consistent, several new tools are available to assist in identifying the underlying etiology. As our understanding of male fertility expands, the technologies available to diagnose and ultimately treat it continue to evolve.

Whole-exome sequencing identified a novel mutation of AURKC in a Chinese family with macrozoospermia

PURPOSE

Macrozoospermia is a rare sperm morphologic abnormality associated with male infertility and is characterized by a high percentage of spermatozoa with large irregular heads. The aim of this study was to identify the genetic cause of an infertile male with macrozoospermia from a consanguineous family.

METHODS

Whole-exome sequencing (WES) was performed using peripheral blood genomic DNA from the patient and his parents.

RESULTS

WES analysis of the patient with macrozoospermia from a consanguineous family allowed the identification of a novel homozygous missense variant in the AURKC gene (c.269G>A). Bioinformatics analysis also suggested this variant a pathogenic mutation. Quantitative real-time PCR analysis showed that the mRNA level of AURKC is significantly decreased in the patient compared with his father. Moreover, no embryos were available for transfer after ICSI.

CONCLUSIONS

These results further support the important role of AURKC in male infertility and guide the practitioner in optimal decision making for patients with macrozoospermia.