Knockout of mouse receptor accessory protein 6 leads to sperm function and morphology defects†

Abstract

Receptor accessory protein 6 (REEP6) is a member of the REEP/Ypt-interacting protein family that we recently identified as essential for normal endoplasmic reticulum homeostasis and protein trafficking in the retina of mice and humans. Interestingly, in addition to the loss of REEP6 in our knockout (KO) mouse model recapitulating the retinal degeneration of humans with REEP6 mutations causing retinitis pigmentosa (RP), we also found that male mice are sterile. Herein, we characterize the infertility caused by loss of Reep6. Expression of both Reep6 mRNA transcripts is present in the testis; however, isoform 1 becomes overexpressed during spermiogenesis. In vitro fertilization assays reveal that Reep6 KO spermatozoa are able to bind the zona pellucida but are only able to fertilize oocytes lacking the zona pellucida. Although spermatogenesis appears normal in KO mice, cauda epididymal spermatozoa have severe motility defects and variable morphological abnormalities, including bent or absent tails. Immunofluorescent staining reveals that REEP6 expression first appears in stage IV tubules within step 15 spermatids, and REEP6 localizes to the connecting piece, midpiece, and annulus of mature spermatozoa. These data reveal an important role for REEP6 in sperm motility and morphology and is the first reported function for a REEP protein in reproductive processes. Additionally, this work identifies a new gene potentially responsible for human infertility and has implications for patients with RP harboring mutations in REEP6.

Knockout of family with sequence similarity 170 member A (Fam170a) causes male subfertility, while Fam170b is dispensable in mice†

“…For scanning transmission electron microscopy (STEM) analysis of the testis, adult male mice were anesthetized and perfused with 2.5% glutaraldehyde in PBS by transcardial perfusion, as we recently described [ 44 ]. Testes were embedded, prepared for ultrathin sectioning, and mounted by the Houston Methodist Research Institute’s Electron Microscopy Core.…”

“…CASAnova uses five kinematic measurements from CASA output files (average path velocity, VAP; curvilinear velocity, VCL; straight line velocity, VSL; amplitude of lateral head, ALH; and beat cross frequency, BCF) to classify sperm into either nonvigorous (slow or weak) or vigorous (progressive, intermediate, or hyperactive) motility patterns. CASAnova was used and analyzed as described previously [ 44 ].…”

Insights into the Mechanism of Bovine Spermiogenesis Based on Comparative Transcriptomic Studies

“…However, the abnormal expression of important functional genes during spermiogenesis affects the morphology [ 6 ] and structure of the sperm and may lead to male sterility [ 7 ]. During spermatogenesis, Brdt binds to acetylated histones through the bromo domain to promote the reorganisation of chromatin remodelling and mRNA processing [ 8 ].…”

Insights into the mechanism of bovine spermiogenesis based on comparative transcriptomic studies

“…However, abnormal expression of some important functional genes during spermiogenesis affects the morphology (6) and structure of the sperm, endanger the function of the sperm, and lead to male sterility (7). The quality standard for frozen bovine semen (GB4143-2008) stipulates that the proportion of morphologically abnormal spermatozoa in qualified bovine semen should be less than 18%, while the Real-World Health Organization Human Semen Analysis Laboratory Technical Manual (Fifth Edition) stipulates that the proportion of morphologically abnormal spermatozoa in human semen should be less than 4%.…”