Biallelic mutations in PMFBP1 cause acephalic spermatozoa

Abstract

The majority of men with defects in spermatogenesis remain undiagnosed. Acephalic spermatozoa is one of the diseases causing primary infertility. However, the causes underlying over half of affected cases remain unclear. Here, we report by whole-exome sequencing the identification of homozygous and compound heterozygous truncating mutations in PMFBP1 of two unrelated individuals with acephalic spermatozoa. PMFBP1 was highly and specifically expressed in human and mouse testis. Furthermore, immunofluorescence staining in sperm from a normal control showed that PMFBP1 localizes to the head-flagella junction region, and the absence of PMFBP1 was confirmed in patients harboring PMFBP1 mutations. In addition, we generated Pmfbp1 knock-out (KO) mice, which we found recapitulate the acephalic sperm phenotype. Label-free quantitative proteomic analysis of testicular sperm from Pmfbp1 KO and control mice showed 124 and 35 proteins, respectively, increased or decreased in sperm from KO mice compared to that found in control mice. Gene ontology analysis indicates that the biological process of Golgi vesicle transport was the most highly enriched in differentially expressed proteins, indicating process defects related to Golgi complex function may disturb formation of the head-neck junction. Collectively, our data indicate that PMFBP1 is necessary for sperm morphology in both humans and mice, and that biallelic truncating mutations in PMFBP1 cause acephalic spermatozoa.

Keywords: PMFBP1; acephalic spermatozoa; consanguineous family; gene knock-out mice; whole-exome sequencing.