Mutations in the stromal antigen 3 (STAG3) gene cause male infertility due to meiotic arrest

• Published in: Human reproduction (Oxford) 2019-11, Vol.34 (11), p.2112-2119
• Main Authors: van der Bijl, N, Röpke, A, Biswas, U, Wöste, M, Jessberger, R, Kliesch, S, Friedrich, C, Tüttelmann, F
• Format: Article
• Language: English
• ISSN: 0268-1161; 1460-2350
• DOI: 10.1093/humrep/dez204

Abstract STUDY QUESTION Are sequence variants in the stromal antigen 3 (STAG3) gene a cause for non-obstructive azoospermia (NOA) in infertile human males? SUMMARY ANSWER Sequence variants affecting protein function of STAG3 cause male infertility due to meiotic arrest. WHAT IS KNOWN ALREADY In both women and men, STAG3 encodes for a meiosis-specific protein that is crucial for the functionality of meiotic cohesin complexes. Sequence variants in STAG3 have been reported to cause meiotic arrest in male and female mice and premature ovarian failure in human females, but not in infertile human males so far. STUDY DESIGN, SIZE, DURATION The full coding region of STAG3 was sequenced directly in a cohort of 28 men with NOA due to meiotic arrest. In addition, a larger group of 275 infertile men that underwent whole-exome sequencing (WES) was screened for potential STAG3 sequence variants. Furthermore, meiotic spreads, immunohistochemistry, WES and population sampling probability (PSAP) have been conducted in the index case. PARTICIPANTS/MATERIALS, SETTING, METHODS This study included 28 infertile but otherwise healthy human males who underwent Sanger sequencing of the full coding region of STAG3. Additionally, WES data of 275 infertile human males with different infertility phenotypes have been screened for relevant STAG3 variants. All participants underwent karyotype analysis and azoospermia factor (AZF) screening in advance. In the index patient, segregation analysis, WES data, PSAP, lab parameters, testis histology and nuclear spreads have been added to suplort the findings. MAIN RESULTS AND THE ROLE OF CHANCE Two compound-heterozygous variants in STAG3 (c.[1262T>G];[1312C>T], p.[(Leu421Arg)];[(Arg438Ter)]) have been found to cause male infertility due to complete bilateral meiotic arrest in an otherwise healthy human male. Compound heterozygosity was confirmed by Sanger sequencing of the parents and the patient’s brother. Other variants which may affect spermatogenesis have been ruled out through analysis of the patient’s WES data and application of the PSAP pipeline. As expected from Stag3 knockout-mice meiotic spreads, germ cells did not develop further than zygotene and showed drastic chromosome aberrations. No rare variants in STAG3 were found in the 275 infertile males with other phenotypes. Our results indicate that STAG3 variants that negatively affect its protein function are a rare cause of NOA (