Azoospermia is a form of male infertility characterized by a complete lack of spermatozoa in the ejaculate. Sertoli cell-only syndrome (SCOS) is the most severe form of azoospermia, where no germ cells are found in the tubules. Recently, FANCM gene variants were reported as novel genetic causes of spermatogenic failure. At the same time, FANCM variants are known to be associated with cancer predisposition. We performed whole-exome sequencing on a male patient diagnosed with SCOS and a healthy father. Two compound heterozygous missense mutations in the FANCM gene were found in the patient, both being inherited from his parents. After the infertility assessment, the patient was diagnosed with diffuse astrocytoma. Immunohistochemical analyses in the testicular and tumor tissues of the patient and adequate controls showed, for the first time, not only the existence of a cytoplasmic and not nuclear pattern of FANCM in astrocytoma but also in non-mitotic neurons. In the testicular tissue of the SCOS patient, cytoplasmic anti-FANCM staining intensity appeared lower than in the control. Our case report raises a novel possibility that the infertile carriers of FANCM gene missense variants could also be prone to cancer development.

The most severe form of male infertility is idiopathic non-obstructive azoospermia (NOA), a complete sperm absence in the ejaculate. We performed exome sequencing in the Croatian infertile brothers with NOA and found a variant in DMRT1 (Doublesex and mab-3 related transcription factor 1) gene that was further assessed by the EMSA assay and molecular dynamic simulations. We additionally screened for DMRT1 mutations in 1940 infertile men diagnosed with spermatogenic failure, 644 normozoospermic controls, and 105 females with primary ovarian insufficiency (POI) recruited to the GEnetics of Male INfertility Initiative (GEMINI) or Estonian Andrology (ESTAND) cohorts. DMRT1 p.Pro74Leu (chr9:g.842059C > T) variant was detected in infertile brothers in the highly conserved position within the DNA binding DM domain of the protein. EMSA assay showed reduced DNA binding of DMRT1P74L and molecular dynamic simulations showed differences in structural and dynamical properties between the wild type protein and DMRT1P74L. Plausible disease-causing DMRT1 variants were only identified in infertile men (13/1940; 0.67%), and none in 639 fertile controls. Burden testing showed an excess of rare deleterious DM domain mutations in the infertility cohort compared to gnomAD v.4.0 population-based controls (Fisher’s exact test, p = 1.44 x 10−5). Three rare deleterious variants in DMRT1 were found in 104 cases of POI. The findings of this study strengthen the evidence of DMRT1 variants being a causal factor for male infertility and provide the distribution of likely pathogenic variants across the gene. This is also the first study to suggest that DMRT1 variants may also be linked to POI.

Sertoli cell-only syndrome (SCOS) is a condition of male infertility characterized by a total absence of spermatogenic cells in nearly all seminiferous tubules. Apart from well-established genetic changes such as Klinefelter syndrome, CFTR variants, and Y-chromosome microdeletions, several hundred candidate genes were reported as associated with male infertility. We selected 92 evidence-based genes associated with infertility and investigated data from whole-exome sequencing in 6 individuals with clinically diagnosed SCOS. Eight heterozygous variants passed our filtering criteria, including population frequency ≤ 0.1% and high functional impact indicated by Sift, Polyphen, and CADD scores. Out of them, we considered only variants with putative autosomal dominant effects on infertility that were subsequently validated by Sanger sequencing. This filtering pipeline has led to the final likely causative variants detected in CHD7 and SCYP3 genes that potentially explain SCOS in two of our patients. Our discoveries suggest that gene panel testing of patients with SCOS could improve the diagnostic outcome; however, assembling a gene panel consisting of only genuine causative genes is crucial.