One direction of our research is to understand the mechanisms by which the sperm motility and male fertility are regulated by ion channels. In particular, we are studying the sperm-specific calcium channels “CatSper”, which are essential for sperm hyperactivation. To identify molecules underlying mammalian sperm hyperactivation, we are using a comparative genomic and proteomic approach to find candidate genes in the CatSper-mediated Ca2+ signaling pathway.

We functionally characterize sperm cells from the mice deficient in candidate genes from the screens. We test fertility by natural mating and IVF, sperm motility in vitro for hyperactivation and sperm rheotaxis, and in vivo for sperm migration. Sperm motility is correlated with functionl and molecular changes using high-speed, high-resolution video microscopy for dynamic optical imaging of fluorescently labeled live cells and super-resolution imaging for molecular distribution in fine detail.

We are also working to understand how CatSper-mediated Ca2+ entry relays spatial information to the axoneme. Spatial control of axonemal proteins that regulate dynein activity could result in the asymmetry of hyperactivated motility. 

Photo credit: Jean-Ju Chung