Short range cell-cell signals and inheritance of cytoplasmic determinants provide the information to specify the three germ layers of embryos. This specification occurs early in cleavage in most embryos but the mechanisms by which the germ layers are established are still in the early stages of discovery. In the sea urchin embryo we have learned that beta-catenin is involved in specification of mesoderm and endoderm. Notch is later necessary for specification of secondary mesoderm cells. This proposal is for studies to learn how these sequential specification events work. There are two specific aims in this proposal:
Aim 1 : To test the hypothesis that nuclear beta-catenin regulates autonomous specification of cells in the vegetal hemisphere during cleavage. All the preliminary evidence supports this hypothesis, however much remains to be learned. How the beta-catenin is activated to enter nuclei and engage in its signaling role is not known. How the required nuclear entry relates to micromere specification and to the known activation of a micromere signal is not known. In macromeres beta-catenin enters nuclei autonomously at the 32-cell stage and these cells also receive a signal from micromeres. The distinct roles of the two signals are not known. Experiments in this section will provide a more complete understanding of how beta-catenin functions autonomously in embryos to activate early specification events.
Aim 2 : To test the hypothesis that Notch acts after beta-catenin to refine the territories in the vegetal hemisphere and to be essential for secondary mesoderm specification. Again, the preliminary data support this hypothesis and provide a number of clues as to how Notch might work in this early germ layer specification role. We will ask how the earlier beta-catenin signal is essential for the later Notch signal in the vegetal hemisphere. The Notch signal is localized and during signaling the molecule is consumed and degraded. Experiments will explore these molecular observations to better understand the mechanism of Notch's function during this mesoderm specification event. An important component of these experiments is to learn how ligands of Notch and regulators of Notch signaling delineate territorial signaling specificity. In addition, we will experimentally challenge a potential cause and effect relationship between Notch and possible downstream targets of Notch signaling, one of which appears to be activation of the Brachyury mesodermal transcription factor.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM061464-03
Application #
6387186
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Program Officer
Zatz, Marion M
Project Start
1999-09-02
Project End
2003-08-31
Budget Start
2001-09-01
Budget End
2002-08-31
Support Year
3
Fiscal Year
2001
Total Cost
$217,770
Indirect Cost
Name
Duke University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
071723621
City
Durham
State
NC
Country
United States
Zip Code
27705
Byrum, Christine A; Xu, Ronghui; Bince, Joanna M et al. (2009) Blocking Dishevelled signaling in the noncanonical Wnt pathway in sea urchins disrupts endoderm formation and spiculogenesis, but not secondary mesoderm formation. Dev Dyn 238:1649-65
Bradham, Cynthia A; Oikonomou, Catherine; Kühn, Alexander et al. (2009) Chordin is required for neural but not axial development in sea urchin embryos. Dev Biol 328:221-33
Walton, Katherine D; Warner, Jacob; Hertzler, Philip H et al. (2009) Hedgehog signaling patterns mesoderm in the sea urchin. Dev Biol 331:26-37
Wu, Shu-Yu; Yang, Yu-Ping; McClay, David R (2008) Twist is an essential regulator of the skeletogenic gene regulatory network in the sea urchin embryo. Dev Biol 319:406-15
Wu, Shu-Yu; McClay, David R (2007) The Snail repressor is required for PMC ingression in the sea urchin embryo. Development 134:1061-70
Croce, Jenifer C; Wu, Shu-Yu; Byrum, Christine et al. (2006) A genome-wide survey of the evolutionarily conserved Wnt pathways in the sea urchin Strongylocentrotus purpuratus. Dev Biol 300:121-31
Byrum, C A; Walton, K D; Robertson, A J et al. (2006) Protein tyrosine and serine-threonine phosphatases in the sea urchin, Strongylocentrotus purpuratus: identification and potential functions. Dev Biol 300:194-218
Beane, Wendy S; Voronina, Ekaterina; Wessel, Gary M et al. (2006) Lineage-specific expansions provide genomic complexity among sea urchin GTPases. Dev Biol 300:165-79
Walton, Katherine D; Croce, Jenifer C; Glenn, Thomas D et al. (2006) Genomics and expression profiles of the Hedgehog and Notch signaling pathways in sea urchin development. Dev Biol 300:153-64
Robertson, Anthony J; Croce, Jenifer; Carbonneau, Seth et al. (2006) The genomic underpinnings of apoptosis in Strongylocentrotus purpuratus. Dev Biol 300:321-34

Showing the most recent 10 out of 16 publications