Johanna Höög, forskare i cellbiologi.
Johanna Höög, researcher in cell biology.
Photo: Malin Arnesson

Johanna Höög wants to understand how human sperm cells can swim


Johanna Höög is an Assistant Professor in Cell Biology. She researches the flagella inside the human sperm cell through high resolution 3D reconstructions.

What's your research about?

'I want to understand how human sperm cells can swim. My research team do high resolution 3D reconstructions of human sperm cells, in particular their tail, which is the motor that propels them forward.'

Why is this so interesting?

'Without functioning sperm tails we wouldn’t exist. I therefore find it incredible that we don’t know what human sperm cells look like in detail. But there are more reasons to study them. Inside the sperm tail there are structures called flagella. We can find flagella in many places of our bodies. For example, flagella are found on the surface of our lungs, and clear the dust and dirt that we inhale every day when we breathe. And it is also flagella that push the egg down the fallopian tube into the womb.'

How did you become interested in this subject?

'I studied the flagella of the African sleeping sickness parasite as a postdoc at University of Oxford. When I looked at my 3D reconstruction of their flagella structure, I saw that they were quite different from the structures seen in the other species that we studied.'

'There was no information on human flagella 3D structure at all at that time. This made me wonder which of these model systems that we study to understand flagella function is actually most similar to the human structure. I studied the literature and realized that there was no information on human flagella 3D structure at all at that time, so this just had to be my future research focus.'

Have you made any interesting discoveries or results?

'We did the very first 3D reconstruction of human sperm cells with cryo-electron tomography in 2018. When we saw the images, we screamed straight out, since inside of it, we saw a structure that had never been seen in flagella before.'

'We screamed straight out, since we saw a structure that had never been seen in flagella before. It was a tiny helical structure that was only located at the very outmost part of the sperm tail. We named it TAILS and we are now trying to figure out what TAILS function is in sperm swimming.'

Have these results surprised you?

'Both yes and no. We knew we were the first researchers ever to look at human sperm cells at this high resolution, so there was a possibility we could discover new and exciting structures. But we had no idea what we would find. This is why our research is so exciting. You can say it is an expedition into the unknown environment inside ourselves.'

What's been the best moment or highlight in your research career so far?

'When I received the funding to start my own laboratory. It felt incredible to be trusted with this opportunity. For a long time, I have had too many research ideas for one person to carry out, and now I have been able to put together a team that all work together to research my ideas.'

How can your research benefit society?

'If the flagella in the body don’t function normally, people become seriously ill. Deafness, infertility and recurring pulmonary infections are just some of the symptoms that can occur if the flagella are dysfunctional.'

'My research tries to understand how the flagellum is structured so that we can understand what goes wrong when it does not work. The flagella diseases together are called PCD. My research tries to understand how the flagellum is structured to perform its movements, so that we can understand what goes wrong when it does not work (PCD). You could compare it with the knowledge of how a motor is constructed to be able to fix a broken car engine. My goal is to produce a technical drawing on the human flagellum, describing its different parts and how they function.'

What are the future challenges in your research field?

'Until now, researches around the world have used a green alga as a model organism to understand how flagella work. This has been a very successful approach in understanding flagella biology, but it is unclear how well these discoveries will help to understand human flagella.'

'In fact, our research shows that there are great differences in the structure of flagella in the green alga and in human flagella. Therefore, we might now have to reassess which model organism is the most suitable to understand human flagellar disease.'