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Biology and MB&B
Graduate Student Career Retreat 2008
Name:
Kristi LaMonica, Maya
Bass, and Laura Grabel
Lab:
Laura Grabel
[Biology]
Abstract
The Planar Cell
Polarity Pathway Regulates Parietal Endoderm Outgrowth
Kristi LaMonica, Maya Bass,
and Laura Grabel
Biology Department, Wesleyan
University
Parietal
extraembryonic endoderm (PE) contributes to the yolk sac and
is the first migratory cell type in the developing mammalian
embryo. We study this migratory event using the F9
teratocarcinoma cell in vitro model system. In
suspension culture, F9 cells form embryoid bodies (EBs)
consisting of an inner core of undifferentiated stem cells,
surrounded by an outer layer of visceral endoderm. When EBs
are plated on extracellular matrix substrates, PE migrates
away from the EB as a sheet of cells that are enriched in
migratory and adhesion structures. To determine if PE
migration is regulated by the PCP pathway, we first
determined if migratory cells were polarized. Based on golgi
localization and microtubule organization, more than 70% of
the outgrowth cells are polarized in the direction of
migration. In the planar cell polarity pathway (PCP), which
mediated directed cell migration events, Wnt ligand binds
the Frizzled receptor activating Disheveled, which activates
Daam1, leading to activation of the Rho/ROCK pathway.
Perturbation of the Wnt pathway using the soluble Frizzled
Receptor (sFRP) increases outgrowth migration distance and
inhibits cell polarity. Our previous data showed that
Rho/ROCK inhibited outgrowth migrates further and faster, as
observed with Wnt inhibition and we now show that under this
condition cells are not polarized. We hypothesize that a Wnt
source in the EB repels emerging PE, promoting outgrowth of
polarized cells. Candidate Wnts, including Wnt 3a, Wnt 5a,
Wnt7a/b, and Wnt 11, implicated in the PCP pathway, are also
expressed in F9 EBs. Currently we are investigating the
location of Wnts and Frizzled receptors in the outgrowth
system and using genetic approaches to perturb the PCP
pathway.
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