The formation of organs during embryonic development is a true multitasking process: the tissue grows and takes on a specific shape. At the same time, each organ requires a precise number of cells and must also be functionally structured in such a way that it can carry out its tasks without errors. Until now, little was known about how embryos manage to spatially and temporally coordinate all these different developments. Now scientists from the Instituto Gulbenkian de Ciência, Portugal, and the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden have made an interesting discovery.
The research team studied the retina of zebrafish embryos and human retinal organoids, small retina-like structures that they grew from human cells in a controlled manner. Both systems, being small and translucent, allow to observe the organization and growth of the tissue in real time. Using light sheet microscopy and the latest image processing technology based on artificial intelligence, the researchers gained initial insights into the cellular behavior of the retina of vertebrates during their growth.
The scientists were able to observe how an entire population of photoreceptors temporarily changed their place and left the place in the tissue where they later have to fulfill their functions. Through this active movement, the nerve cells created space for newly arriving progenitor cells, which divided in the vacated area and thus produced more cells that later contributed to the retina. If the movement of the photoreceptors was blocked, cell congestion occurred, which forced the progenitor cells to divide in the wrong place and led to tissue malformations. Without the temporary relocation of the photoreceptors, the development of a healthy retina was not possible.
“This is an exciting migration phenomenon in which nerve cells move on, only to then return to their starting point,” says Mauricio Rocha-Martins, first author of the study from the MPI Dresden. “It shows that, contrary to previous scientific assumptions, neuronal migration not only moves nerve cells to the right place, but also plays a direct role in the coordination of organ development.”
The simultaneity of growth and the alignment of organ structure to future tasks characterizes the development of almost all organs. Based on the new research results, it can be investigated whether other organs use similar cell mechanisms. In addition, the findings show that faulty nerve cell migration can lead to major damage. For example, it was already known to be the reason for severe brain malformations in humans. Research into the interaction of cells is now all the more important for understanding the causes of human developmental disorders.