Seeing eye development
Researchers from the European Molecular Biology Laboratory (EMBL) have discovered important new processes in the development of eyes. Eyes are amongst the most complex structures in living things. Their development still triggers debate over the way evolution progresses, as eyes seem to have evolved far more quickly than other organs. This research looks specifically into the development of the eye in the transparent embryos of Medaka fish. The researchers, from the EMBL laboratory in Heidelberg, have found cells programmed specifically to develop into eyes at very early stages of development. When eyes develop in most animals, the brain first appears as a tube, and the eyes form as growths from that tube. 'You can think of the tube as a deflated balloon shaped like a Mickey Mouse,' explains Jochen Wittbrodt, who led the EMBL team. 'As the fish grows, the eyes gradually bulge out from the tube, the way Mickey Mouse ears expand as a balloon is filled with air. Most scientists have thought that cells in the neighbouring regions grow to make the bulges. What we've seen is that individual cells migrate to this area from the central region of the tube - as if to make ears, tiny rubber particles had to fly out from the air inside the balloon.' The EMBL team tracked individual cells using an advanced microscope technique. Previous EMBL research had identified a protein, known as Rx3, essential for eye development. The team stained cells producing this protein with a fluorescent dye, and then followed them using a microscope to track cell movement, and build a three dimensional film of the cell migration using advanced software developed by Richard Adams from Cambridge University. 'Rx3 plays a crucial role in giving the cells their identity and telling them where to go,' said Martina Rembold, who conducted the staining procedure. 'Normally, single cells migrate actively and one-by-one from the centre of the brain to form eyes. But in strains of fish that have no Rx3, no eyes develop and the cells remain inside the brain, because nothing tells them to migrate to the right place.' The Rx3 protein effectively guides the cells to the right place, where it beings to form the eye. All cells will have similar markers, to move them snugly to the right parts of the developing embryo. Previously, research had indicated that sheets or groups of cells would grow into nascent body parts. This research, published in the journal Science, suggests that migration may be more common than previously thought. 'We know that cell migration is important in the formation of many other organs, such as the heart,' explains Dr Wittbrodt. 'We'd like to understand how tissues originate and how cells move in the early embryo and to decipher the cues that tell them where to go. This approach of tracking individual cells will help us to understand these processes better.'
Countries
Germany, United Kingdom