Recent Yale research has shed light on the movement of sperm cells in the female reproductive tract of mice.
The study, published on Feb. 22 in the journal eLife, shows that when a particular subunit of the ion channel surrounding the sperm cell, called CatSper, is disrupted, sperm movement is impaired and can lead to lower fertility rates. The research has implications for human fertility, given the similarity of human sperm cell movement to that of mouse sperms cells.
Yale School of Medicine professor and lead author of the study Jean-Ju Chung said that, although her background is in the signaling of ion channels and membrane receptors, she is particularly interested in the CatSper ion channel. She added that because CatSper genes are in humans as well as mice, a mutation in the gene coding for the channel proteins means humans may also show male-specific infertility.
Chung stressed the importance of the channel — which displays selective permeability to calcium ions — to human fertility, adding that in the study, she investigated two particular subunits of this CatSper calcium channel in relation to sperm cells, specifically.
“We find that if one component is missing, the normally distributed continuous alignment and the compartmentalization of the sperm channel is disrupted and fragmented, and that results in reduced calcium current,” Chung said. “Because the alignment of the CatSper channel is broken in the reduced calcium current, the signaling propagation is inefficient and the shape of the regular envelope is transformed to a rod with a 3-D waveform, and the [sperm cells] cannot withstand fluid flow in the female body.”
According to the study, the researchers were able to partially rescue against fluid flow. Chung said that there are some factors in the female fluid which can boost the CatSper dependent calcium signaling pathway.
She added that the research may allow treatment of infertility in patients experiencing problems associated with the calcium channel, such as calcium failing. She added that the study may aid in the development of drugs.
Chung described the difficulty associated with studying the CatSper ion channel, noting that because cloned cells cannot be used to study it, original sperm cells must be used.
She pointed out that only a handful of groups in the world are studying the CatSper channel, adding that she intends to follow up this study with further investigation of the channel assembly.
“This is one main part of the current research,” she said. “I have three or four research projects going on, and there’s a following up research on this as well. We are also looking for CatSper channel assembly, looking for CatSper structure biogenesis … Basically, we are using molecular and cellular tools and lots of advanced imaging, for example the high-speed microscope imaging, to look for defects and how the signaling went wrong when there is a defect.”
According to the National Institutes of Health, complete lack of sperm occurs in approximately 10 to 15 percent of infertile men.