Formation of polarized epithelium is fundamental to embryonic development. During mouse peri- implantation development, the undifferentiated inner cell mass of the blastocyst is converted from a nonpolar cell aggregate to a highly organized epithelial cyst. This morphogenetic transformation involves the polarization and basement membrane (BM)-dependent survival of epiblast epithelium. However, the molecular mechanisms underlying these processes are largely unknown. The mouse peri-implantation development can be recapitulated by in vitro cultured embryoid bodies (EBs) differentiated from embryonic stem cells. Using genetically modified EBs, we show for the first time that BM formation directs the assembly of an adhesion complex, which serves as a signaling platform to regulate epiblast polarization and survival. Our preliminary data supporting this idea, demonstrating that (1) assembly of the BM-associated adhesion complexes correlates with the activation of Rho GTPases Cdc42 and Rac1;(2) Cdc42 controls microtubule organization and the trafficking of apical polarity proteins, processes that are required for cell elongation and polarization;and (3) Rac1 activation plays an essential role in BM-dependent epiblast survival. These data strongly support our hypothesis that BM formation induces epiblast polarization and promotes epiblast survival via activation of Cdc42 and Rac1. To test this hypothesis, we propose to determine the mechanism through which the assembly of BM-associated adhesion complexes induces Cdc42 and Rac1 activation (Specific Aim 1 and 3). Next, we will determine the Cdc42-effector interactions that regulate epiblast elongation and apical polarization, focusing on the role of IQGAP1 in microtubule capture and the exocyst in apical polarity protein trafficking (Specific Aim 2). Finally, we will determine the Rac1- effector interactions that regulate epiblast survival (Specific Aim 4). The long-term goal of this study is to identify the extracellular cues and the transmembrane cascades that regulate embryonic epithelial morphogenesis, which are crucial to our understanding of epithelial biology, embryogenesis, and tissue regeneration. Public Health Relevance: Elucidating the molecular mechanisms of embryonic epithelial tissue formation that integrate cellular polarity, differentiation and survival with tissue architecture is not only critical to our understanding of embryonic development and cancer biology but also has implications in tissue regeneration and tissue engineering.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM081674-03
Application #
7894474
Study Section
Special Emphasis Panel (ZRG1-ICI-D (01))
Program Officer
Maas, Stefan
Project Start
2008-09-01
Project End
2012-08-31
Budget Start
2010-09-01
Budget End
2011-08-31
Support Year
3
Fiscal Year
2010
Total Cost
$308,880
Indirect Cost
Name
University of Medicine & Dentistry of NJ
Department
Surgery
Type
Schools of Medicine
DUNS #
617022384
City
Piscataway
State
NJ
Country
United States
Zip Code
08854
Li, Shaohua; Qi, Yanmei; McKee, Karen et al. (2017) Integrin and dystroglycan compensate each other to mediate laminin-dependent basement membrane assembly and epiblast polarization. Matrix Biol 57-58:272-284
Qi, Y; Liu, J; Saadat, S et al. (2015) PTEN induces apoptosis and cavitation via HIF-2-dependent Bnip3 upregulation during epithelial lumen formation. Cell Death Differ 22:875-84
Rong, Li; Liu, Jie; Qi, Yanmei et al. (2012) GATA-6 promotes cell survival by up-regulating BMP-2 expression during embryonic stem cell differentiation. Mol Biol Cell 23:3754-63
Qi, Yanmei; Tian, Xiaoxiang; Liu, Jie et al. (2012) Bnip3 and AIF cooperate to induce apoptosis and cavitation during epithelial morphogenesis. J Cell Biol 198:103-14
Liu, Jie; He, Xiaowen; Qi, Yanmei et al. (2011) Talin1 regulates integrin turnover to promote embryonic epithelial morphogenesis. Mol Cell Biol 31:3366-77
Qi, Yanmei; Liu, Jie; Wu, Xunwei et al. (2011) Cdc42 controls vascular network assembly through protein kinase C? during embryonic vasculogenesis. Arterioscler Thromb Vasc Biol 31:1861-70
He, Xiaowen; Liu, Jie; Qi, Yanmei et al. (2010) Rac1 is essential for basement membrane-dependent epiblast survival. Mol Cell Biol 30:3569-81
Liu, Jie; He, Xiaowen; Corbett, Siobhan A et al. (2009) Integrins are required for the differentiation of visceral endoderm. J Cell Sci 122:233-42