Dr. Andreas Merdes
Centre de Biologie du Développement
UMR5547: CNRS/ Université de Toulouse
Bat4R3, 118 route de Narbonne
31062, Toulouse, France
amerdes at cict.fr
Phone: +33 (0)5 61 55 82 65
Fax: +33 (0)5 61 55 65 07
Cell division in eukaryotes requires the assembly of a mitotic spindle, i.e. a bipolar apparatus of microtubules and associated proteins. In animal cells, the formation of the mitotic spindle is induced from two small microtubule-organizing structures, the centrosomes. Each centrosome consists itself of two cylindrically shaped ‘centrioles’ that are surrounded by an amorphous protein matrix, the pericentriolar material. It is believed that proteins of this pericentriolar material are ultimately responsible for the nucleation and anchorage of microtubules.
The function of gamma-tubulin complexes
In our research group, we investigate the composition and function of the pericentriolar material. In particular, we are interested in multiprotein complexes formed by gamma-tubulin, a member of the large tubulin family. Gamma-tubulin complexes catalyse the nucleation of microtubules, which is particularly important at the onset of mitosis for the formation of a functional spindle apparatus. In addition, we have recently found that gamma-tubulin complexes can bind along the length of microtubules where they contribute to microtubule stability. Gamma-tubulin is associated with additional ‘gamma-tubulin complex proteins’ (GCPs). A small complex (‘gamma-tubulin small complex’ or ‘gamma-TuSC’) is formed of two molecules of gamma-tubulin, bound to the proteins GCP2 and GCP3. A larger complex is found in many higher eukaryotes that resembles a ring structure, the ‘gamma-tubulin ring complex’ or ‘gamma-TuRC’. This gamma-TuRC is composed of several gamma-TuSCs and additional proteins, including GCP4, GCP5, GCP6, NEDD1 (=GCP-WD), and others.
Dynamics of centrosome proteins in the cell cycle and in differentiation
A second line of research focuses on the dynamics of centrosome assembly. We study factors that regulate centrosome assembly and maturation during the cell cycle, and during differentiation. At the onset of mitosis, proteins of the gamma-tubulin complex accumulate at the pericentriolar material, to support the formation of the spindle apparatus. In differentiating cells such as muscle or skin cells, a complete reorganization the pericentriolar material is observed. In muscle, centrosome proteins relocalize to the outer nuclear surface. Current research is performed to determine the mechanisms of centrosomal protein assembly during mitosis and differentiation.