Novel and recurrent hemizygous variants in BCORL1 cause oligoasthenoteratozoospermia by interfering transcription.

Background: Oligoasthenoteratozoospermia (OAT) is a common cause of male infertility, of which the causes remain largely unknown. Recently, BCORL1 was identified as a contributor to male infertility from non-obstructive azoospermia (NOA) to OAT.

Objectives: To identify novel and hotspot variants in BCORL1 from infertile men with OAT and reveal their outcomes of assisted reproductive treatments (ARTs).

Materials and methods: Forty-six infertile men characterized by OAT were recruited from 2017 to 2022. Variants in OAT patients were identified by whole-exome sequencing (WES) and verified by Sanger sequencing. Papanicolaou staining was used for sperm morphology analysis. Pathogenicity of BCORL1 variants were analyzed by bioinformatics analysis, and further confirmed in vitro by using recombinant plasmids and cells. Meanwhile, ARTs were performed on these patients to investigate the appropriate clinical treatment strategy.

Results: We identified a novel hemizygous missense variant (NM_021946: c.G4171A; p.G1391R) and a recurrent variant (NM_021946: c.T2615G; p.V872G) in BCORL1 from four OAT patients. Notably, routine semen assessment and Papanicolaou staining revealed a special OAT phenotype of patients with BCORL1 variants, whose rare mature sperm characterized by acephalic and abnormal acrosome. Pathogenicity analysis showed the interaction between BCORL1 with histone deacetylases (HDACs) were disrupted after variance, accompanied with epigenetic alterations and finally the orderly transcriptions of spermatogenetic genes were interfering. Besides, clinical record presented the poor outcomes of ARTs in these patients with BCORL1 variants.

Discussion and conclusions: Our findings further expand the variant spectrum of BCORL1 related to OAT, and provide new evidences that BCORL1 acts as an important transcriptional regulator, participating in epigenetic regulation and directing the expression of key genes throughout spermatogenesis. The outcomes of ARTs will facilitate the genetic counseling and clinical treatment of infertile men with BCORL1 variants in the future.