Dresden 2009 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 8: Developmental Processes

BP 8.2: Hauptvortrag

Dienstag, 24. März 2009, 10:00–10:30, HÜL 186

The R8 race: Specifying photoreceptor cells in the developing fly eye — •David Lubensky — University of Michigan, Ann Arbor, MI, USA

Regular patterns of cell fate appear widely in biology. Such patterns also emerge spontaneously, via a Turing instability, in models of diffusible activators and inhibitors, but it remains unclear to what extent biology takes advantage of this fact. I will discuss a quantitative analysis of Drosophila eye development, focusing on the activator-inhibitor system responsible for spacing the R8 photoreceptors that define the eye’s regular ommatidial pattern. The R8 lattice grows by turning on the expression of proneural genes at a moving front to create new columns of R8 cells. I propose a model where R8 fate specification occurs when a bistable genetic switch is flipped in a given cell; a template of inhibitory signals from the existing R8 lattice determines where the switch will be flipped in the new column. A consequence of our model is that transient perturbations of one column can change the pattern in all subsequent columns. Most strikingly, the normal triangular lattice can give way to stripes of R8 cells. These predictions are confirmed experimentally by manipulation of the Notch and scabrous genes. In our model, the relative timing and strength of signals from the template, rather than competition among neighboring cells, determines the eventual R8. If time allows, I will discuss implications of this picture for other related examples of neural fate specification.