SCIENCE AT THE EDGE SEMINAR SERIES

Quantitative Biology / Gene Expression in Development & Disease Seminar

Friday, 04 November 2011 at 11:30am

Room 1400 Biomedical and Physical Sciences Bldg.

Refreshments at 11:15

Speaker: Smadar Ben Tabou de Leon,
         Department of Biology, California Institute of Technology 

Title:   Spatio-Temporal Information Processing in
         Developmental Gene Regulatory Networks

Abstract:

One of the earliest events in embryo development is the formation of distinct
axes along which different lineages are defined. In many cases, the initial
symmetry breaking along the major axis of the embryo is induced by asymmetric
activity of highly conserved signaling pathways; for example, the Wnt pathway
control of the anterior-posterior patterning and the BMP pathway control of
the dorsal-ventral patterning. In order to understand how signaling activity
is translated into specific regulatory states and cell fate decisions, the
downstream gene regulatory network activated by the signals has to be
explored. In this talk I will discuss the spatio-temporal information
processing in two regulatory networks that specify the major axes in the sea
urchin embryo: (1) The regulation of the animal-vegetal axis formation and
endoderm specification by the wnt-{beta}catenin pathway and its downstream
regulatory network. (2) The regulation of the oral-aboral (ventral-dorsal)
axis formation and the aboral ectoderm specification by the BMP pathway and
its downstream regulatory network. Interestingly, these two networks present
opposite modes of regulatory control by the signaling pathways. The spatial
expression of the endodermal regulatory genes is directly controlled by Wnt
signaling (through de-repression of Tcf), while the differential temporal
expression profiles of these genes are controlled by their unique activators.
On the other hand, the temporal expression profiles of the aboral regulatory
genes is directly controlled by the BMP pathway (through SMAD1/5/8
phosphorylation), while the differential spatial expression of these genes is
controlled by additional mechanisms. In both cases, the signaling pathway that
defines the axis controls directly either a common spatial expression or a
common temporal profile of a set of downstream regulatory genes, possibly to
lead to a clear cut cell fate decision.