FLAGELLAR MOTION AND THE FINE STRUCTURE OF MOUSE SPERM
Aichi University of Education, Japan
Cilia and flagella are microtubule-based organelles that extend from the surface of eukaryotic cells. The movement is generated by microtubule sliding with axonemal dynein motors, and plays important roles in cell migration and generation of external fluid flow. Since cilia and flagella have diverse roles in many tissues and organs in mammal, defects in ciliary and flagellar activity causes a number of diseases called ciliopathy. Especially, the motility of sperm flagella is rerated to reproduction, so the defect of the motility causes infertility. The mouse sperm is composed of three continuous pieces, mid-piece including spherical mitochondria, principal piece, and end piece. The glycolysis has an important role in providing the ATP required sperm motility.
In this study, we investigated the three dimensional structure of mouse sperm flagella using cryo-electron tomography and image analysis. We obtained some tomograms and calculated the averaged images. We found that the radial spoke structure in mouse sperm flagella was different compared to the structure of axoneme in the other organisms. We also try to analyze the motility of mouse sperm flagellar in the high-viscosity using methylcellulose. In order to understand the flagellar motion of mouse sperm in the high viscosity solution more precisely, we analyzed the motion using high speed camera, and calculated the beat frequency and the amplitude of the flagellar waveform. In the case of unloaded condition, the beat frequency and amplitude of principal piece was higher than mid-piece. While the beat frequency and amplitude of sperm flagella decrease in the high-viscosity condition, the beat frequency was not changed in the presence of 2-Deoxy-D-glucose (DOG) which is inhibitor of glycolysis. Therefore, the mitochondrial ATP production tends to maintain the beat frequency with decrease of the amplitude of sperm flagellar waveform.