IQCN disruption causes fertilization failure and male infertility due to manchette assembly defect

Abstract

Total fertilization failure (TFF) is an important cause of infertility; however, the genetic basis of TFF caused by male factors remains to be clarified. In this study, whole‐exome sequencing was firstly used to screen for genetic causes of TFF after intracytoplasmic sperm injection (ICSI), and homozygous variants in the novel gene IQ motif‐containing N ( IQCN ) were identified in two affected individuals with abnormal acrosome structures. Then, Iqcn ‐knockout mice were generated by CRISPR‐Cas9 technology and showed that the knockout male mice resembled the human phenotypes. Additionally, we found that IQCN regulates microtubule nucleation during manchette assembly via calmodulin and related calmodulin‐binding proteins, which resulted in head deformity with aberrant oocyte activation factor PLCζ. Fortunately, ICSI with assisted oocyte activation can overcome IQCN‐associate TFF and male infertility. Thus, our study firstly identified the function of IQCN , highlights the relationship between the manchette assembly and fertilization, and provides a genetic marker and a therapeutic option for male‐source TFF. image Homozygous pathogenic variants in IQCN were identified in two male patients experiencing TFF. IQCN was found essential for regulating nucleation during microtubule assembly by interacting with calmodulin and calmodulin‐related binding proteins. The two affected individuals showed an increased proportion of sperm head malformations and characteristics of a ruffled acrosome. Abnormal acrosome caused aberrant oocyte activation factor PLCζ localization and TFF after ICSI. The phenotype of Iqcn‐knockout ( Iqcn −/− ) male mice is similar to that of the affected individuals. IQCN interacts with calmodulin to promote prolonged manchette assembly in spermatids, and the disappearance of this interaction leads to nucleation defects. IQCN‐related male infertility could be rescued by ICSI with assisted oocyte activation.