The research of our group is focussed on the role of tubulin posttranslational modifications in the regulation of the functions of the microtubule cytoskeleton. In the past years, our group has discovered and characterised many of the enzymes that are involved in the catalysis of two complex tubulin modifications, polyglutamylation and polyglycylation. Our first functional studies using these enzymes have revealed important implications of both, polyglutamylation and polyglycylation in different functions of the microtubule cytoskeleton. We are now focussing on dissection of the molecular mechanisms that underlie the potential regulatory roles of these modifications. In parallel, we are focussing on the investigation of the functional roles of tubulin modifications in cells, organism development and disease. The complexity of these modifications might provide a fine-tuning mechanism for interactions between microtubules and their binding partners, the molecular motors and MAPs.