Meiotic segregation in spermatozoa of a 46,X,t(Y;10)(q11.2;p15.2) fertile translocation carrier

[Assessment of the man in the infertile couple]

BACKGROUND

Among couples consulting for infertility, there is a male component, either alone or associated with a female aetiology in around one in 2 cases.

MATERIAL AND METHODS

Bibliographic search in PubMed using the keywords "male infertility", "diagnosis", "management" and "evaluation" limited to clinical articles in English and French prior to 1/01/2023.

RESULTS

The AFU recommends: (1) a complete medical history including: family history, patient history affecting fertility, lifestyle habits (toxicity), treatments, symptoms, sexual dysfunctions; (2) a physical examination including: BMI, signs of hypogonadism, secondary sexual characteristics, scrotal examination (volume and consistency of testes, vas deferens, epididymal or testicular nodules, presence of varicocele); (3) two spermograms, if abnormal on the first; (4) a systematic scrotal ultrasound,± an endorectal ultrasound depending on the clinic; (5) a hormonal work-up (testosterone, FSH; if testosterone is low: LH assay to differentiate between central or peripheral hypogonadism); (6) karyotype if sperm concentration≤10 million/mL; (7) evaluation of Y chromosome microdeletions if concentration≤1 million/mL; (8) evaluation of the CFTR gene in cases of suspected bilateral or unilateral agenesis of the vas deferens and seminal vesicles. The role and usefulness of direct and indirect tests to assess the effects of oxidative stress on sperm DNA will also be explained.

CONCLUSION

This review complements and updates the AFU/SALF 2021 recommendations.

Azoospermia and reciprocal translocations: should whole-exome sequencing be recommended?

Background

Although chromosome rearrangements are responsible for spermatogenesis failure, their impact depends greatly on the chromosomes involved. At present, karyotyping and Y chromosome microdeletion screening are the first-line genetic tests for patients with non-obstructive azoospermia. Although it is generally acknowledged that X or Y chromosome rearrangements lead to meiotic arrest and thus rule out any chance of sperm retrieval after a testicular biopsy, we currently lack markers for the likelihood of testicular sperm extraction (TESE) in patients with other chromosome rearrangements.

Results

We investigated the use of a single nucleotide polymorphism comparative genome hybridization array (SNP-CGH) and whole-exome sequencing (WES) for two patients with non-obstructive azoospermia and testicular meiotic arrest, a reciprocal translocation: t(X;21) and t(20;22), and an unsuccessful TESE. No additional gene defects were identified for the t(X;21) carrier - suggesting that t(X;21) alone damages spermatogenesis. In contrast, the highly consanguineous t(20;22) carrier had two deleterious homozygous variants in the TMPRSS9 gene; these might have contributed to testicular meiotic arrest. Genetic defect was confirmed with Sanger sequencing and immunohistochemical assessments on testicular tissue sections.

Conclusions

Firstly, TMPRSS9 gene defects might impact spermatogenesis. Secondly, as a function of the chromosome breakpoints for azoospermic patients with chromosome rearrangements, provision of the best possible genetic counselling means that genetic testing should not be limited to karyotyping. Given the risks associated with TESE, it is essential to perform WES - especially for consanguineous patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12610-021-00145-5.

Preimplantation genetic diagnosis for a carrier of a Y;autosome translocation resulting in a healthy male offspring

OBJECTIVE

To demonstrate the feasibility of establishing a successful pregnancy for a carrier of a balanced Y;autosome translocation.

DESIGN

Four locus-specific fluorescence in situ hybridization (FISH) probes, informative for the translocation, were identified and tested on peripheral lymphocyte metaphase chromosomes and interphase preparations from the translocation carrier and his partner.

SETTING

National health service genetics center, cytogenetics laboratory, and assisted conception unit.

PATIENT(S)

An infertile man, presenting with a balanced Y;13 translocation, and his reproductive partner.

INTERVENTION(S)

After ovarian stimulation, 15 eggs were collected, nine were injected, and three were suitable for blastomere biopsy on day 3; a single blastomere was taken from each embryo and tested with four locus-specific FISH probes.

MAIN OUTCOME MEASURE(S)

Birth of a healthy child.

RESULT(S)

One embryo showed a triploid signal pattern and one had fragmented nuclei; neither was suitable for transfer. One embryo showed a balanced male signal pattern and was transferred. A singleton pregnancy was established, resulting in the birth of a healthy male child.

CONCLUSION(S)

This first report of successful preimplantation genetic diagnosis treatment for infertile males with y:autosome translocations demonstrates that this treatment option can result in successful pregnancies and healthy offspring.