Diminished ovarian reserve (DOR) and primary ovarian insufficiency (POI) are major causes of female infertility. We recently found a monogenic etiology in 29.3% of POI, leading to personalized medicine. The genetic landscape of DOR is unknown. A prospective study (2018–2023) of an international cohort of 120 patients with unexplained DOR was performed using a large custom targeted next-generation sequencing panel including all known POI-causing genes. The diagnostic yield, based on the American College of Medical Genetics, was 24, 2%. Genes belong to different pathways: metabolism and mitochondria (29.7%), follicular growth (24.3%), DNA repair/meiosis (18.9%), aging (16.2%), ovarian development (8.1%), and autophagy (2.7%). Five genes were recurrently found: LMNA, ERCC6, SOX8, POLG, and BMPR1B. Six genes identified in single families with POI were involved in DOR, GNAS, TGFBR3, XPNPEP2, EXO1, BNC1, ATG, highlighting their role in maintaining ovarian reserve. In our cohort, 26 pregnancies were recorded, but no pregnancy was observed when meiosis/DNA repair genes were involved, suggesting severely impaired oocyte quality. Additional studies should confirm these preliminary results. This study with a large NGS panel defines the genetic landscape of a large cohort of DOR. It supports routine genetic diagnosis. Genetics could be a biomarker predicting infertility and progression to POI.

The use of next-generation sequencing (NGS) has recently enabled the discovery of genetic causes of primary ovarian insufficiency (POI) with high genetic heterogeneity. In contrast, the causes of diminished ovarian reserve (DOR) remain poorly understood. Here, we identified by NGS and whole exome sequencing (WES) the cause of isolated DOR in a 14-year-old patient. Two frameshift mutations in BRCA1 (NM_007294.4) were found: in exon 8 (c.470_471del; p.Ser157Ter) and in exon 11 (c.791_794del, p.Ser264MetfsTer33). Unexpectedly, the patient presented no signs of Fanconi anemia (FA), i.e., no developmental abnormalities or indications of bone marrow failure. However, high chromosomal fragility was found in the patient’s cells, consistent with an FA diagnosis. RT-PCR and Western-blot analysis support the fact that the c. 791_794del BRCA1 allele is transcribed and translated into a shorter protein (del11q), while no expression of the full-length BRCA1 protein was found. DNA damage response (DDR) studies after genotoxic agents demonstrate normal activation of the early stages of the DDR and FANC/BRCA pathway. This is consistent with the maintenance of residual repair activity for the del11q BRCA1 isoform. Our observation is the first implication of bi-allelic BRCA1 mutations in isolated ovarian dysfunction or infertility in humans, without clinical signs of FA, and highlights the importance of BRCA1 in ovarian development and function.

Study question: To identify the etiology of isolated Primary Ovarian Insufficiency (POI) in a patient from an Indian consanguineous family. Summary answer: A homozygous nonsense mutation of SPIDR in the patient yielded chromosomal instability: first evidence of a role of this gene in DNA repair. What is known already: POI, affecting 1% of women under 40, is a public health problem. To date ∼ 70% of cases remain idiopathic. The leap due to exome sequencing, led to the identification of ∼ 80 genes, often in single or few cases. SPIDR was recently identified as a scaffolding protein connecting RAD51, a central player in homologous recombination, to BLM, a helicase implicated in the integrity of the genome. But its precise role is still unknown. A SPIDR mutation was previously associated with POI. However, contradictory conclusions were reported on the mechanism of SPIDR action and on its pathogenic role in POI. Study design, size, duration: Prospective genetic study of a cohort of 150 pateints with POI worldwide using a custom-made targeted next generation sequencing (NGS) panel comprising 60 known POI-causing genes. A single patient was found mutated in SPIDR. Cytogenetic studies were performed to analyse the consequences of the mutation on DNA repair and sister chromatide exchanges (SCE). Participants/materials, setting, methods: The patient with SPIDR mutation had POI with primary amenorrhea, delayed puberty and streaks ovaries. She was born to consanguineous Indian parents. No other mutation was detected in our cohort of 150 patients with POI. Targeted NGS was performed in the proposita. Familial segregation was performed by Sanger sequencing. Mitomycin C (MMC)-induced chromosomal breakages were studied and a sister chromatid exchange (SCE) assay was performed in patient’s peripheral lymphocytes. Main results and the role of chance: We identified a novel homozygous nonsense mutation in the exon 7 of SPIDR (KIAA0146) c.814C>T, R272*, predicted to yield either a truncated protein, or a non-sense-mediated mRNA decay. The patient’s cells display increased chromosomal fragility with high MMC-induced chromosomal breaks when compared to a control. Remarkably, there was no increased SCE. In the previous report of a SPIDR mutation in POI, no cytogenetic studies were performed, and contradictory results were obtained on a homologous recombination test between the two sisters, either enhanced or reduced. In conclusion, we show here that inactivation of SPIDR results in a defect of double strand DNA damage repair, similar to alteration of the RAD51 pathway. There was no increased SCE, the hallmark of the BLM pathway. This observation has major consequences for this patient’s care : indeed mutations of DNA-repair genes may also yield to tumors/cancers. A long follow-up of the patient is needed in a multidisciplinary team to detect possible comorbidities. Indeed, even in the absence of somatic symptomatology, the patient has enhanced chromosomal instability highlighted by cytogenetic studies, that may yield tumor-predisposition. Limitations, reasons for caution: No other mutation of SPIDR in the replication cohort of 150 POI patients. SPIDR mutation are thus very rare world-wide. Wider implications of the findings: This is the first evidence of chromosomal instability associated with SPIDR defect, providing strong evidence for a role of SPIDR in double strand DNA damage repair in humans and for its causal role in POI. Our study improves the knowledge on SPIDR function and confirms its involvement in POI worldwide. Trial registration number: Not applicable