| Early in development an embryo must transform itself from an outwardly uniform ball of cells to a series of precisely patterned tissues. Behind this transformation lies a complex network of genes that are activated and repressed in specific spatial and temporal patterns. Using the Xenopus laevis model, my thesis research has focused on identifying and describing the genes that carry out these early patterning processes. To that end, I have followed two main research lines. The first is a study of GREUL1, a protein that can induce anterior tissues types in neurulating embryos. To better understand the role of this gene in development, I isolate X. laevis GREUL1, and show that it shares the inductive ability of mouse GREUL1 and is expressed in the most anterior tissue of X. laevis embryos, the cement gland. These results indicate that GREUL1 is likely to play a role in the patterning of anterior ectodermal tissues in X. laevis. The second research line takes a broader perspective and uses emerging genomic technologies to describe the suites of genes that underlie embryo patterning during gastrulation, using manipulations of the primary gastrula patterning center, the organizer. This approach identifies new organizer-related genes and allows me to better dissect the roles of the two main organizer activities BMP and Wnt inhibition. My results show that BMP inhibition acts early, initiating the suites of genes that pattern dorsal tissues, while Wnt inhibition acts later during gastrulation, and is essential for maintenance of organizer gene expression throughout gastrulation. |
