Genetic networks and the flow of positional information in embryonic development

by Prof. William Bialek (Princeton University)

Tuesday 6 Jun 2017, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dip. di Fisica - Edificio G. Marconi)

The emergence of a fully functional organism from a single cell is one of the most beautiful phenomena in Nature.  In the fruit fly, this happens in twenty four hours, and we can see a blueprint for the segmented body plan emerging in just three hours.  In this system, it is possible to measure quite accurately the concentrations of particular molecules that encode the position of each cell in the embryo. These concentrations are the outputs of a genetic network, and they are present at very low concentrations, so that the random arrival of these molecules at their targets is a significant source of noise, limiting the transmission of positional information.   Putting ourselves in the place of the cells, we have been able to "read the code," building a dictionary that maps gene expression levels back into estimates of position. We can test our dictionary by studying mutant flies that are missing one or two of the primary inputs to the network.  In these mutants, the spatial patterns of gene expression are distorted, and our dictionary turns this into a distorted map of inferred position vs. actual position.  If we are right, then the fly should follow this map and put structures in the wrong places; experiments show strikingly quantitative agreement with these predictions.  These results are part of a larger effort to think about how the architecture and parameters of the underlying genetic network have been chosen to optimize information transmission.

 

Joint work with CG Callan, JO Dubuis, T Gregor, D Krotov, M Petkova, TR Sokolowski, G Tkacik, AM Walczak, and EF Wieschaus.