A Long contiguous stretches of homozygosity disclosed a novel biallelic pathogenic variant in STAG3 causing Primary Ovarian Insufficiency

Abstract Background: Primary ovarian insufficiency (POI) refers to an etiologically heterogeneous disorder characterized by hypergonadotropic hypogonadism that represents a major cause of infertility in women under 40 years. Most cases of isolated POI still appear sporadically, but ∼10–15% have an affected first-degree relative, indicating a significant genetic etiology. Several genes implicated in development, meiosis, hormonal signaling and metabolism are involved in the genetic form of the disorder in both syndromic and isolated POI. However, most cases of POI remain unsolved even after exhaustive investigation. Results: Here is reported a 19-year-old Senegalese female affected by non-syndromic POI showing primary amenorrhoea, who well answered to the hormonal induction of puberty reaching a complete sexual maturation in two years. In order to investigate the presence of a genetic defect, aCGH-SNP analysis was performed. A 13.5 Mb long contiguous stretch of homozygosity (LCSH) region on chromosome 7q21.13-q22.1 was identified where the exome sequencing revealed a novel homozygous 4-bp deletion (c.3381_3384delAGAA) in STAG3 . Pathogenic variants in this gene, encoding for a meiosis-specific protein, have been previously reported as cause POI in only seven families and recently as cause of infertility in a male. The here identified mutation leads to the truncation of the last 55 aminoacids, confirming the important role in meiosis of the STAG3 C-terminal domain. Conclusions: In conclusion we identified a loss of function variant in STAG3 in a Senegalese woman with POI reinforcing the role the cohesin complex in the genetic etiology of this disorder. This gene should be included in the screening of POI to offer a better genetic counseling and long term follow-up considering the risk of ovarian tumor in woman carrying pathogenic variants in genes involved in germ cell differentiation.