Morphological phenotypes and changes in motility parameters of sperms in Fscb/Cabyr double knockout mice

Abstract

Objective To investigate the changes in morphological characteristics of sperm flagellum and in sperm motility parameters in Fscb/Cabyr double gene knockout (Fscb/Cabyr--/--) mice. Methods The testis and epididymis tissues of male mice with different genotypes were collected and the organ-to-body weight ratio was calculated. The changes of spermatogenesis function in the testicular tissues of the mice were observed using HE staining. The parameters of sperm motility were analyzed using a computer-aided sperm analysis (CASA) system, and sperm capacitation and acrosome reaction were observed with in vitro culture. The morphological characteristics of the sperms under optical microscope and electron microscope were compared among the mice with different genotypes. Results No significant difference was found in sperm density in the epididymis among the mice with 5 different genotypes. The progressive rate (PR) and motility rate (PR+NP), mean curvilinear velocity (VCL), mean straight-line velocity (VSL), mean path velocity (VAP), beat cross frequency (BCF) and amplitude of lateral head displacement (ALH) of the sperms were significantly lower in Fscb/Cabyr--/-- and Fscb/Cabyr++/-- mice than in the wild-type mice (P < 0.01). The Fscb/Cabyr--/-- and Fscb/Cabyr++/-- mice showed significantly lowered percentages of normal sperms 1.45)% and (53.22±3.51)%] as compared with the wild-type mice and significantly higher rates of sperm tail folding] than the wild-type mice. Ultrastructural observation of the sperm flagellum in Fscb/Cabyr--/-- and Fscb/Cabyr++/-- mice revealed that the longitudinal columns of the fibrous sheath disappeared in most of the sperms with disorganized circumferential ribs and heterogeneous reduction of the electron density in the sperms; some sperms showed disruption of the axoneme structure in the flagella with occasional disappearance and dissociation of the doublet microtubules at the center. Conclusion Both Cabyr single gene knockout and Fscb/Cabyr double gene knockout can cause significant abnormalities in flagellum morphology and motility of the sperms in male mice. CABYR protein is essential for maintaining normal fibrous sheath structure and normal motility of the sperm flagella.

Keywords

• gene knockout
• sperm
• fibrous sheath
• morphology
• motility