Homozygous deleterious variants in MYCBPAP induce asthenoteratozoospermia involving abnormal acrosome biogenesis, manchette structure and sperm tail assembly in humans and mice.

Asthenoteratozoospermia is a common cause of male infertility. To further define the genetic causes underlying asthenoteratozoospermia, we performed whole-exome sequencing in a cohort of Han Chinese men with asthenoteratozoospermia. Homozygous deleterious variants of MYCBPAP were first identified in two unrelated Chinese cases. Replication analyses in a French cohort revealed an additional asthenoter-atozoospermia-affected case harboring a homozygous nonsense variant in MYCBPAP. All of the identified MYCBPAP variants were absent or extremely rare in the public human genome databases. Further functional assays indicated remarkably reduced abundance of MYCBPAP in the spermatozoa from MYCBPAP-associated cases. Subsequently, we generated a Mycbpap knockout (Mycbpap^-/-) mouse model, which also exhibited male infertility with reduced sperm motility and abnormal morphologies in sperm heads and flagella. Further investigations demonstrated that Mycbpap^-/- male mice presented disrupted acrosome biogenesis and abnormally elongated manchette during spermiogenesis. Intriguingly, proteomic analyses indicated that the proteins related to spermatogenesis, acrosomal and flagellar functions were significantly down-regulated in the testes from Mycbpap^-/- male mice. Endogenous immunoprecipitation combined with mass spectrometry revealed interactions of MYCBPAP with a ribosome elimination related protein ARMC3 and central apparatus proteins including CFAP65 and CFAP70. Furthermore, MYCBPAP-associated male infertility in humans and mice could be partially overcome by using intracytoplasmic sperm injections. Collectively, these findings illustrate the essential role of MYCBPAP in normal spermatogenesis and homozygous deleterious variants in MYCBPAP can be considered as a genetic diagnostic indicator for infertile men with asthenoteratozoospermia. Our study will provide effective guidance for genetic counseling, clinical diagnosis and assisted reproduction treatments of MYCBPAP-associated male infertility.