Evolution of Cell Types
Animals are composed of multifarious types of cells, which serve highly specific functions and may form part of tissues and organs or may occur singly. In our group we are interested in the evolution of this complexity. Which cell types correspond to each other in phylogenetic distinct animals? Which insights can we get in the organization of ancestral forms? How did cell types change over time in different evolutionary lineages and how do arise new cell types?
To fulfill their specialized tasks cells show various molecular and structural adaptions and type specific sets of genes pattern their development. We thus collect integrative data from different invertebrate taxa to trace cell type evolution. We combine gene expression analysis with electron microscopic and functional studies. Beside getting insights into the evolutionary history we also obtain intriguing data on the plasticity of cell types on the molecular, the structural and the functional level. Currently we focus on:
1) The evolution of photoreceptor cells and eyes in Bilateria. The debate how animal light sensing organs emerged is nearly as old as the debate about the principle of evolution. Integrative molecular and structural work offers now the chance to decipher eye evolution on the cellular level and it became clear that many traditional hypotheses have to be modified thoroughly. Different kinds of photoreceptor cells can be traced back to ancient times giving insights into the evolutionary roots of animal light dependent reactions. Obviously, both things happened during ongoing evolution. Certain photoreceptors became considerably reorganized, whereas others changed their functional context.
2) The evolution of chitin secreting cells in protostomes. Animals use chitin either to build protective covers like e.g. the arthropod cuticle or to form highly ornamented structures like e.g. the bristles of annelids. While cuticles are formed by standard epidermal cells, structures like the annelid bristles are generated by very specialized and dynamic cells. We try to identify differences in the molecular machinery between these modes of chitin secretion and their evolutionary origin.