Me, that’s Theresa, medium-sized, medium-blonde, in my mid-30s. And after what felt like 280 years, she actually got her amazing doctoral hat. Her dissertation was about the question of how certain transcription factors, i.e. Proteins that bind to DNA and control the activity of many other genes, help ensure that functional nerve cells form druing embryonic development.
After fertilization, an egg cell begins to divide and initially forms a cluster of cells in which all cells initially look the same. But at some point after further division and shifting, a rudimentary body shape can suddenly be recognized. A head forms at one end and a kind of tail at the other. The cells develop into different types that later perform certain functions in certain positions in the body: for example, a beta cell in the pancreas produces insulin, while a skin cell contributes to our external mechanical and chemical protective layer. In (developmental) biology we call this process, in which stem cells develop into cells of different tissue types, differentiation.
And on this path, in the case of my dissertation when differentiating from a stem cell to a mature neuron, the cell encounters a wide variety of influences that arise due to its position in the embryo. For example, neighboring cells send very specific signalling substances that meet receptors on the outside of the target cell: these are proteins that protrude through the cell membrane and react externally to the presence of a signal substance, whereupon they trigger a response inside of the cell. This answer usually leads to the activation of transcription factors, which in turn will switch other genes on or off. These other genes can now be very specific for a particular cell type; in the case of beta cells, for example, the gene for insulin.
In my dissertation I focused on the role of a very specific transcription factor, Brain-specific Homeobox (Bsx). As the name suggests, the Bsx gene is only read in the brain. In this article you can read in detail what the “Homeobox” and the functions of Bsx are all about.
Understanding the interaction of transcription factors during differentiation can be helpful, for example, when treating people in whom nerve cells degenerate. The first symptoms of Parkinson’s disease do not appear until more than 70% of all dopamine-producing neurons in the midbrain have died. Contrary to popular belief, stem cells are now relatively easy, inexpensive and can be generated without serious ethical concerns. For example, it has been possible for a number of years to “reprogram” differentiated skin cells until they can no longer be distinguished from embryonic stem cells (more on that here). Thus, stem cells can be generated from any patient of any age. In addition, humans (although this was not believed for a long time) lifelong have stem cell populations in the brain (as well as in all other organs) from which new nerve cells can arise. In other words, allowing stem cells to develop into dopaminergic neurons in a targeted manner, regardless of their origin, has enormous clinical significance.
Scientists in the biomedical fields usually have to choose a research model, since humans, as the object to which the main interest relates, can only be examined to a quite limited extent. My model of choice was the zebrafish, which is also called Danio rerio by zoologists inclined to Latin and which became one of the most popular laboratory animals of geneticists and developmental biologists over the last few decades. One of the reasons for this is that zebrafish can score points with very high numbers of offspring; a motivated zebrafish couple likes to lay 500 eggs in one morning. Egg-laying also makes the work (well, first of all the egg collection) easy for the embryologist. In a mammal, the eggs or embryos are much more difficult to access. In addition, zebrafish eggs are relatively large, which makes them easy to manipulate (genetically) and the embryo that forms from the egg has almost all organs fully formed within just a few days. Probably the greatest thing about these small zebrafish larvae is that they remain completely transparent for quite some time. Microscopic recordings of the developing organs in the living larvae over long periods of time are therefore not only possible, but standard in zebrafish developmental biology.
In addition to genes and zebrafish, Theresa is particularly interested in areas in which science meets society. This ranges from popular science writing, philosophy of science and ethical components of current biological and biotechnological research to points of contact between science and art. If you want to talk to Theresa about any of these topics, ideally with caffeinated hot drinks or – due to any geographical differences – via modern communication methods, please contact her.