Remote controlled sperm
How sperm gear themselves up to fertilise an egg is very difficult to study. For a start, standardising the conditions and then being able to reproducibly study each sperm cell without unintentionally altering its biochemistry is extremely tricky.
Now a German team have come up with a way to make remote controlled sperm that you can turn on with a flash of light. Joining Chris Smith from the Center of Advanced European Studies and Research, Germany, is Dr. Dagmar Wachten, who led the study...
Dagmar - Hello.
Chris - Why on Earth would you want, first of all to make remote controlled sperm? What was your motivation?
Dagmar - That's a good question. So, what we tried was basically to have a tool that we can use to control sperm function and that is not disturbed by any other means. Here light is the easiest way to do that because you can quickly turn it on and off.
Chris - If you were to use drugs or other chemicals on the sperm to control their activity, I suppose there might be side effects.
Dagmar - Yes, that's true because sperm are not really easy to handle and they're really prone to odd effects in particular, when you use pharmacological tools. And that's why we want to step away from that and then use light.
Chris - How does one go about making sperm sensitive to light so you can turn them on and off in this way?
Dagmar - So, the first thing you need to do, we need to engineer them and you need to genetically do that by introducing a molecule that is light-sensitive. Usually, sperm don't contain light-sensitive molecules. So, what we did, we use the light-sensitive molecule that allowed us to control sperm motility. Just by shining light on them, we could speed up the sperm so they swim faster.
Chris - How do you get the light sensitive molecule into the sperm in the first place?
Dagmar - So, we would need to do here a transgenic approach. Meaning, we would need to engineer a fertilised oocyte. So, we introduce a piece of DNA into this oocyte and from this create a new mouse and this mouse then contains this light-sensitive molecule just in its sperm.
Chris - I see. So, by putting the gene for the light-sensitive molecule into the mouse in the first place then its sperm are naturally produced with this particular molecule in them. And they're only activated essentially, when you shine the light on them then.
Dagmar - Yeah. So, what we do is we prep those sperm, those genetically engineered sperm in the dark and in the dark they're completely behaving normally like normal sperm would do. But only when we shine light on them, these sperm swim faster because their tails are beating faster.
Chris - What is this showing you? What can you do with these sperm now that we couldn't do before?
Dagmar - So before, it was really tricky to study particular signalling pathways in sperm and analyse which molecules control which sperm function. Now, having this tool, we can just really precisely switch on a particular sperm function namely, sperm motility and understand how this is regulated in a really precise manner.
Chris - And I suppose that this may have a long term benefit for people who potentially suffer from say, subfertility or infertility because the more we understand about how sperm work, the better place we are to try to develop better treatments.
Dagmar - Of course! First, we want to understand what is going wrong in those patients because so far, our understanding is not sufficient to really say what is going wrong in a particular patient. So, that's the first thing we need to understand.
Chris - Dagmar, thank you very much. That's Dagmar Wachten, describing the world's first remote controlled sperm, just activated by light, a study that she published just recently in the journal eLife.