The beating of eukaryotic flagella depends on the sliding movements between microtubules powered by dynein. In flagella of most organisms, microtubule sliding is regulated by the internal structure of flagella comprising the central pair of microtubules and radial spokes. It has been shown that the deletion of a part of radial spokes from sperm cells inhibits the beating motion of flagella. Here, we report the swimming motility of non-motile sperm cells in a knockout mouse model. The cells lacked a part of radial spoke 1 in sperm flagella, due to the deletion of Iqub . We diluted the sperm cells in a medium, and then enclosed in the high-pressure chamber for optical microscopy. At 0.1 MPa and 37°C, the sperm cells were unable to swim in solution with weak flagellar motility. At 60 MPa, a certain number of the cells started to swim unidirectionally in solution. The swimming speed of the cells was ∼30 μm s −1 , which was approximately one-fifth of that of wild-type cells under physiological conditions. After the pressure release, all the cells stopped swimming. This is consistent with our previous results in Chlamydomonas paralyzed-flagella mutants. Furthermore, the swimming speed of human sperm cells was also increased by ∼10% at 5 MPa. Thus, the application of pressures could activate the flagellar motility across species.
Masayoshi Nishiyama (Sun,) studied this question.