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Kolloquium Physik & Chemie mit Nobelpreisträgerin

Im Rahmen des gemeinsamen Institutskolloquiums der Physik und Chemie spricht am Mittwoch, dem 01. Februar 2017, um 17:15 Uhr im Faraday-Hörsaal Nobelpreisträgerin Prof. Dr. Christiane Nüsslein-Volhard, Max-Planck-Institut für Entwicklungsbiologie Tübingen, zum Thema „Gradient models in developmental biology: a historical perspective“.

Zum Vortrag:
„Gradient models in developmental biology: a historical perspective“ By the beginning of the 20th century, it had been recognized that the final pattern of cell differentiation in the embryo was established through a gradual process during which initially simple patterns were elaborated to achieve increasingly greater complexity. Boveri suggested that cell decisions might depend on a graded distribution of some substance in the egg (Boveri, 1901). Spemann in the 1920 discovered an organizer region in the newt embryo that could influence its surrounding whereby the distance from the organizer determined the fate of the cells. In 1952, Turing proposed a mathematical model to explain morphogenesis by chemical interactions. This famous reaction-diffusion (RD) model is based on an autocatalytic “morphogen” interacting with an inhibitor with higher diffusibility. This model, importantly, fails in size regulation, and cannot explain real patterns. In 1969 Wolpert coined the term positional information and proposed the french flag model of a diffusible gradient of a morphogen that elicits different responses depending on its concentration, and Crick (1970) calculated that a simple source-andsink model could work to establish linear gradients in developmental fields. About the nature of such morphogens could only be speculated, and for many biologists gradients were utterly unpopular because attempts at isolating morphogens had failed so far. Gierer and Meinhardt (1972) proposed their gradient theory of local activation and lateral inhibition, based on non-linear kinetics and able to explain many biological patterns including scaling. In insects eggs, mirror image duplications obtained after experimental manipulations pointed to the existence of gradients determining the long and short egg axis (Sander 1972), which was supported by mutant phenotypes in Drosophila (Nüsslein-Volhard 1979). In fact, the first morphogen discovered was the product of the bicoid gene (Driever and Nüsslein-Volhard 1988), a transcription factor produced by a RNA source localized at the anterior pole of the Drosophila egg. It spreads towards the posterior and activates target genes in a concentration dependent manner. The gradient models of Meinhardt failed to explain the development of the early Drosophila embryo because genetic analysis revealed a strong influence of localized maternal determinants rather than selforganisation. However, in frog and fish embryos activator-inhibitor systems have been identified and the experimental data fit the models very well.