Dataset Information

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

ABSTRACT:

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.

SUBMITTER: Ghieh F

PROVIDER: S-EPMC8582189 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Nonobstructive azoospermia (NOA) is a severe condition in infertile men, and increasing numbers of causative genes have been identified during the last few decades. Although certain causative genes can explain the presence of NOA in some patients, a proportion of NOA patients remain to be addressed. This study aimed to investigate potential high-risk genes associated with spermatogenesis in idiopathic NOA patients by whole-exome sequencing. Whole-exome sequencing was performed in 46 male patients diagnosed with NOA. First, screening was performed for 119 genes known to be related to male infertility. Next, further screening was performed to determine potential high-risk causative genes for NOA by comparisons with 68 healthy male controls. Finally, risk genes with high/specific expression in the testes were selected and their expression fluctuations during spermatogenesis were graphed. The frequency of cystic fibrosis transmembrane conductance regulator (CFTR) gene pathogenic variant carriers was higher in the NOA patients compared with the healthy controls. Potential risk genes that may be causes of NOA were identified, including seven genes that were highly/specifically expressed in the testes. Four risk genes previously reported to be involved in spermatogenesis (MutS homolog 5 [MSH5], cilia- and flagella-associated protein 54 [CFAP54], MAP7 domain containing 3 [MAP7D3], and coiled-coil domain containing 33 [CCDC33]) and three novel risk genes (coiled-coil domain containing 168 [CCDC168], chromosome 16 open reading frame 96 [C16orf96], and serine protease 48 [PRSS48]) were identified to be highly or specifically expressed in the testes and significantly different in the 46 NOA patients compared with 68 healthy controls. This study on clinical NOA patients provides further evidence for the four previously reported risk genes. The present findings pave the way for further functional investigations and provide candidate risk genes for genetic diagnosis of NOA.