Messages diffuse faster than messengers: The case of the bicoid protein

SILVINA PONCE DAWSON

Exposición; Coloquios del Center for Studies in Physics and Biology,Rockefeller University; 2015

The diffusive transport of substances plays a relevant role in manybiological processes. This is particularly important in embryogenesiswhere the spatially inhomogeneous distribution of substances called"morphogens" establishes the pattern for the subsequent celldifferentiation. Most often morphogens do not diffuse freely in thecytosol but also interact with various cell components. The nettransport, in such a case, can be described by effective diffusioncoefficients that depend on the morphogen concentration. A casestudied in great detail is that of the establishment of thedorso-ventral axis in embryos of Drosophila melanogaster where thegradient of the transcription factor, Bicoid, is key. Measurements of theBcd diffusion coefficient using different optical techniques provided estimatesthat differed by an order of magnitude. In this talk I will show how these apparentlycontradictory results can be interpreted within a unified framework by assumingthat Bicoid diffuses and interacts with binging sites. To this end I will discuss whatinformation the different optical techniques provide on the net transport ofsubstances that diffuse and react and how this can be applied to the case of Bicoid.