Biallelic mutations inARMC12cause asthenozoospermia and multiple midpiece defects in humans and mice

Abstract

BackgroundAsthenozoospermia is a major factor contributing to male infertility. The mitochondrial sheath (MS), an important organelle in the midpiece of spermatozoa, is crucial to sperm motility. ARMC12 is a mitochondrial peripheral membrane protein. Deletion ofArmc12impairs the arrangement of MS and causes infertility in mice. However, the role ofARMC12in human asthenozoospermia remains unknown.ObjectiveTo study the genetic defects in patients with asthenozoospermia.MethodsA total of 125 patients with asthenozoospermia and 120 men with proven fertility were recruited. Whole-exome sequencing and Sanger sequencing were performed for genetic analysis. Papanicolaou staining, HE staining, immunofluorescent staining, transmission electron microscopy and field emission scanning electron microscopy were employed to observe the morphological and structural defects of the spermatozoa and testes.Armc12-knockout mice were generated using the CRISPR-Cas9 system. Intracytoplasmic sperm injection was used to treat the patients.ResultsBiallelicARMC12mutations were identified in three patients, including homozygous mutations in two siblings from a consanguineous family and compound heterozygous mutations in one sporadic patient. ARMC12 is mainly expressed in the midpiece of elongated and late spermatids in the human testis. The patients’ spermatozoa displayed multiple midpiece defects, including absent MS and central pair, scattered or forked axoneme and incomplete plasma membrane. Spermatozoa fromArmc12-/-mice showed parallel defects in the midpiece. Moreover, two patients were treated with intracytoplasmic sperm injection and achieved good outcomes.ConclusionOur findings prove for the first time that defects inARMC12cause asthenozoospermia and multiple midpiece defects in humans.