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Poster Full Abstracts - Cell Biology and Signal Transduction
Poster board number is above title. The first author is the presenter
194
chain spaghetti squash (sqh) and par-1 and, remarkably, found that active Sqh strongly suppresses par-1-dependent mutant phenotypes. We show that Par-1
regulates dynamic subcellular localization of Sqh in live BCs and also regulates Myo-II activity. Specifically, Par-1 phosphorylates and inactivates myosin
phosphatase, thus promoting phosphorylation of Sqh and increased Myo-II activation. Finally, Par-1 localizes to and increases active Myo-II at the cluster
rear to promote detachment; in the absence of Par-1, spatially distinct active Myo-II is reduced. Our study reveals that Par-1 regulates polarized Myo-II
activity by localized inhibition of myosin phosphatase, thus modulating the spatiotemporal actomyosin dynamics required for collective BC migration.
229A
WASH, a Rho1 effector, functions through the Arp2/3 complex in hemocyte migration.
James J Watts, Evelyn Rodriguez-Mesa, Susan M Parkhurst.
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA.
The Wiskott Aldrich Syndrome (WAS) family of proteins has been shown to affect the cortical actin cytoskeleton and plasma membrane during
endocytosis and cell migration. We recently characterized a new member of the WAS family, WASH, which acts downstream of Rho1, activates the Arp2/3
complex, and crosslinks microtubules and actin filaments. To examine WASH’s role in migration, we study the hemocytes of the Drosophila embryo.
Hemocytes undergo highly stereotyped developmental migrations in stage 12 to 16 embryos, and they can be induced to migrate towards wounds. We utilize
GFP and RNAi constructs driven solely in hemocytes to track their migration and knockdown WASH, respectively. WASH knockdown causes disruptions
to both induced and developmental migrations including defects in migration direction and cell polarity. Consistent with our previous study, knockdowns of
Rho1 or Arp3 result in similar migration defects, suggesting that WASH acts downstream of Rho1 to activate the Arp2/3 complex in this context. We
confirmed this finding by reproducing the migration defects of WASH knockdown in a Rho1 null embryo rescued by a Rho1 point mutant that retains most
of its function except for its ability to activate WASH. We plan on determining the mechanism through which WASH affects migration direction and cell
polarity utilizing a recently characterized hemocyte cell line.
230B
Fkbp14
is Required for
Drosophila
Development and Interacts with the Notch Pathway.
Julia M Bonner
1,2
, Diana L van de Hoef
1,2
, Gabrielle L
Boulianne
1,2
. 1) Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada; 2) Department of Molecular Genetics,
University of Toronto.
FK506 binding proteins (FKBPs) are a large, highly conserved family of proteins involved in a wide array of biochemical processes including protein
folding, assembly, and trafficking. Little is known regarding many FKBP
in vivo
functions or binding partners, nor the extent and specificity with which they
contribute to metazoan development. We identified a member of this family,
Fkbp14
, in a screen for novel interactors with
presenilin
(
psn
), a key
component of the Notch pathway. We demonstrate that
Fkbp14
genetically interacts with members of the Notch signaling pathway, and observed “escaper”
mutants display classic Notch phenotypes including reduced adult sensory structures, as well as defects in wing margin specification. Initial investigations
indicate that
Fkbp14
-null mutations are homozygous lethal and show dramatically reduced PSN protein levels, while clonal analysis has revealed a severely
reduced cell-viability phenotype. These results indicate a novel requirement for
Fkbp14
in
Drosophila
development. Further investigation into the function
and regulation of
Fkbp14
will provide valuable insight into FKBPs and their significance in development and disease in multicellular systems.
231C
Interactions between MEF2, SD, VG and the Notch pathway during Indirect Flight Muscle development.
Charlotte Caine, Joel Silber, Alexis
Lalouette. Develomental And Molecular Biology, Institut Jacques Monod, PARIS, France.
Myogenesis of indirect flight muscles (IFM) in Drosophila melanogaster follows a well defined cellular developmental scheme. During embryogenesis, a
subset of cells, the Adult Muscle Precursors (AMPs), are specified. These cells will become proliferating myoblasts during the larval stages which will then
give rise to the adult IFM. Although the cellular aspect of this developmental process is well studied, the molecular biology behind the different stages is still
under investigation. We are currently working on the interactions required during the transition between proliferating myoblasts to differentiated myoblasts
ready to fuse to the muscle fiber. It has been previously shown that proliferating myoblasts express the Notch pathway, and that this pathway is inhibited in
developing muscle fibers. On the other hand, it has also been shown that the Myocyte Enhancing Factor 2 (MEF2), Vestigial (VG) and Scalloped (SD)
transcription factors are necessary for IFM development and that VG is required for Notch pathway repression in differentiating fibers. Our study focuses on
the interactions between Notch and MEF2 and mechanisms by which the Notch pathway is inhibited during differentiation. Here we show that MEF2 is
capable of inhibiting the Notch pathway in non myogenic cells. A previous screen for MEF2 potential targets identified Delta and Neuralized, two
components of the Notch pathway. Both are expressed in developing fibers where MEF2, SD and VG are expressed. Our preliminary results show that
MEF2 is required for Delta expression in developing IFMs and that this regulation is potentially dependent on an enhancer to which MEF2 and SD bind. We
have identified a similar Neuralized enhancer that seems to be potentially regulated by MEF2. We are currently studying the effect of MEF2 on these targets
in vivo and in vitro to understand the role they play during IFM differentiation.
232A
The role of Notch signaling in primary pigment cell formation.
Yu-Huei Ho
1
, Jui-Chou Hsu
1,2
. 1) Institute of Molecular Medicine, Department of Life
Science, National Tsing Hua University, Hsinchu, Taiwan 30013, Republic of China; 2) Department of Biological Science and Technology, National Chiao
Tung University, Hsinchu,Taiwan 30013, Republic of China.
Notch signaling is a highly conserved pathway in regulating cell differentiation. In pupal eye, Notch is required for the differentiation of the primary
pigment cell (PPC), whose differentiation is proposed to be induced by receiving Delta from the neighboring cone cells. So far, the detailed mechanism is
unknown. Here we show that the activation of Notch signaling during the time window of PPC selection induces extra enlarged cells outside of the PPC,
phenocopying PPCs, suggesting that Notch induces cell enlargement to differentiate as PPC. However, through live imaging, we found that the activation of
Notch is not sufficient to specify cells as PPCs, implying that Notch needs to combine other signaling to specify PPC. Moreover, we also find that Notch has
different contributions, including selection, enlargement and protection, to PPC formation at different development stages by analyzing the temperature
sensitive allele of Notch at different time points. Collectively, we had further clarified Notch functions during PPC selection.