Evolution and development of glial cells in Platynereis dumerilii (Annelida)

The evolutionary origin of animal nervous systems is a highly relevant and still intensely debated topic. Specifically, the question whether complex centralized nervous systems evolved once or several times independently during bilaterian evolution remains unanswered so far. Interestingly, most of the investigations dealing with this topic in the past solely focussed on characteristics of the neuronal cells. So far, they leave out another important cell type, which is known to be present in most bilaterian nervous systems – the glia cells.

Interestingly, numerous recent studies have shown that glial cells are as important for the nervous system function and development as the neurons themselves. Nevertheless, it is still unknown whether glial cells in deuterostomes and protostomes – the two main clades of Nephrozoa – share a common origin or have evolved convergently. Furthermore, a consistent nomenclature of glia cell types is still missing due to the lack of data and homology statements. With the work on Drosophila (Ecdysozoa) and mammals (Deuterostomia), data on glial cell function and gene expression are so far only available for two of the tree main clades of Nephrozoa. Notably, data for Lophotrochozoa – the third important nephrozoan main clade - are still missing.

Hence, comprehensive datasets for Lophotrochozoa are highly needed to understand the evolution of bilaterian glia cells. To gain insights into glia cell diversity in Lophotrochozoa, I therefore propose to work on glia cells and their development in the model annelid Platynereis dumerilii. For this purpose, I want to use comprehensive methods including in situ hybridization techniques and immunohistochemical stainings with customized as well as standard antibodies. Furthermore, we want to apply ImmunoGold labelling, transmission electron microscopy (TEM) and subsequent 3D analyses on ultrastructural level to investigate the glia cells, their ultrastructure as well as their fate in different stages of Platynereis. With this broad approach, the project will provide highly needed data, a set of lophotrochozoan glia relevant genes and glia specific customized antibodies and first insights into lophotrochozoan glia evolution. Furthermore, we will build up the backbone for further comparative approaches in glia cell research. Additionally, this project will allow a clarification concerning the homology of glia cells in Bilateria in general.