Whole-exome sequencing identifies ADGB as a novel causative gene for male infertility in humans: from motility to fertilization

Objectives: In male mice, adgb-knockout has been reported to cause male infertility with spermatogenesis defects involving flagella and acrosome. However, this remains unclear for humans. Materials and methods: Sequencing studies were conducted in a research hospital on samples from three unrelated infertile men with severe asthenoteratozoospermia from Han Chinese families. Data were collected through rigorous in silico analysis. Sanger sequencing were performed to identify pathogenic mutations. Sperm cells from patients were characterized using electron microscopy and used to verify the pathogenicity of the genetic factors through functional assays. Intracytoplasmic sperm injections (ICSI) assays were performed in ADGB-affected males. Main results: Herein, in a cohort of 105 Han Chinese men with idiopathic asthenoteratozoospermia, we reported the identification of bi-allelic deleterious variants of ADGB in three infertile men from unrelated families using whole-exome sequencing. We found one homozygous frameshift ADGB variant (NM_024694.4: c.2801_2802del:p.K934Rfs*33), one homozygous missense ADGB variant (NM_024694.4: c.C3167T:p.T1056I), and one compound heterozygous ADGB variant (NM_024694.4: c.C3167T:p.T1056I; c.C3197T:p.A1066V). These variants were rare in general population and were predicted to be damaging by multiple bioinformatics tools. Further, the spermatozoa from patients harboring ADGB variants showed multiple acrosome and flagellum malformations under light and electron microscopy. Functional assays revealed the structural defects associated with dysregulation of ADGB and multiple spermatogenesis proteins. Notably, the fertilization success via ICSI treatment in all three patients, as well as the normal expression of PLC zeta but CaM deficiency in the spermatozoa, suggesting that ICSI other than in vitro fertilization (IVF) is an optimal treatment for ADGB-deficient patients. Discussion and conclusio: nOur findings provide new information for the molecular diagnosis of asthenoteratozoospermia and valuable reference for personalized genetic counselling and clinical treatment for these patients. The underlying risk of IVF failure behind sperm defects was highlighted.