Building Gene Regulatory Networks in Development: Deploying Small GTPases
A focused analysis on RhoA, a monomeric GTPase, shows it contributes to multiple signal transduction pathways during sea urchin development. The data reveal that RhoA inhibition in the sea urchin results in a failure to invaginate during gastrulation. Conversely, activated RhoA induces precocious archenteron invagination, complete with the associated actin rearrangements and extracellular matrix secretion. Although RhoA regulates convergent extension movements in vertebrates, our experiments show RhoA activity does not regulate convergent extension in the sea urchin. Instead, the results suggest RhoA serves as a trigger to initiate invagination, and once initiation occurs RhoA activity is no longer involved in subsequent gastrulation movements.
RhoA signaling was also observed during endomesodermal specification in the sea urchin. Data show that LvRhoA activity is required, downstream of a partially characterized Early Signal, for SoxB1 clearance from endomesodermal nuclei (and subsequent expression of GataE and Endo16 genes). Investigations also suggest that within the endomesoderm, RhoA clears SoxB1 as part of Wnt8 signaling, as activated RhoA is sufficient to rescue Wnt8-inhibited embryos. These data provide evidence of the first molecular components involved in SoxB1 clearance, as well as highlight a previously unrecognized role for RhoA during endomesodermal specification. These analyses suggest RhoA signaling is integral to the proper specification and morphogenesis of the sea urchin endomesoderm.
Advisor:McClay, David R.
School Location:USA - North Carolina
Source Type:Master's Thesis
Keywords:biology cell molecular gastrulation endomesodermal specification urchin annotation rhoa calcium signaling
Date of Publication:02/19/2007