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Poster Full Abstracts - Cell Biology and Signal Transduction
Poster board number is above title. The first author is the presenter
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importance of coordinated action between PTP52F and TER94. Our studies for the first time reveal a novel regulatory role of a RPTP that contributes to
proper tissue organization of midgut formation in
Drosophila
metamorphosis.
270C
FGF and EGF signaling pathway act together to regulate Drosophila adult muscle patterning.
Kumar Vishal, Carli Calderon, Zachary Jump, Brian
Gallagher, Joyce Fernandes. Dept Zoology, Maimi Univ, Oxford, OH.
The long term goal of our lab is to understand the hierarchy of interaction among motor neurons, founder cells and myoblasts that leads to fiber patterning
of Indirect flight muscles of the thorax. Our preliminary studies indicate that MAP kinase is activated in the nascent fibers and myoblasts during a period of
active IFM myogenesis (16-20hrs APF). Since, FGF and EGF act through canonical MAP kinase pathway; we are exploring the involvement of
corresponding signaling pathway. We have expressed dominant negative receptors of FGF and EGF pathways in the founder cell and monitored fiber
number. We observed a reduction in number of one groups of IFM fibers, the DLM fibers in both cases. 80% of animals with dominant negative EGFR
expression have 3 or 4 fibers n=8, whereas, 50 % of animals with dominant negative FGF expression have 5 fibers, n=8) as compared to the control (100%
of animals have 6 fibers, n=8). Extra fibers were observed in the IFM groups, the DVMs, 35% of the experimental animals have 4 fibers, whereas 100% of
controls have 3 fibers, n= 6. The results suggest that FGF and EGF regulate adult fiber number and have different effects on DLMs and DVMs, which
develop using distinct modes of myogenesis. We are currently examining muscle patterning during the 0 to 24 hrs APF to determine what aspects of
patterning are disrupted. Myoblast proliferation will be monitored by BrdU incorporation assay, whereas fusion of myoblasts to form nascent fibers will be
studied using antibodies to the transcription factor, erect wing. Additionally we will also examine MAP kinase levels under these manipulated conditions.
271A
RhoGAP68F inhibits endocytic recycling to promote epithelial elongation during metamorphosis.
Beatriz Hernandez de Madrid, Lina Greenberg,
Victor Hatini. Anatomy and Cell Biology, Tufts University, Boston, MA.
Epithelial elongation is a conserved morphogenetic process that contributes to the axial lengthening of embryonic and adult structures. It is mediated by
polarized changes in cell shape, cell proliferation, cell death and rearrangements of cell-cell contacts. All these processes are associated with extensive
remodeling of the cell cortex but the mechanisms involved remain poorly understood. The Drosophila leg imaginal disc elongates dramatically during
metamorphic development to form the leg shaft from a flattened epithelial disc. We investigate the role of RhoGTPases and their regulators the RhoGEFs
and RhoGAP in leg elongation owing to their role in regulating cell adhesion, vesicle transport and cytoskeletal dynamics. We have previously found that
the tarsal region of adult legs depleted for RhoGAP68F are shorter than wild type and have fused joints. To understand the role of RhoGAP68F in epithelial
elongation, we characterized the cell biological roles of RhoGAP68F in vivo and in S2 cells. We found that RhoGAP68F localized to Rab4 recycling
endosomes and formed a complex with Rab4 and constitutively active Rab4 but not with dominant negative Rab4. Over expression of RhoGAP68F led to
enlargement and clustering of Rab4 endosomes, while depletion of RhoGAP68F led to the accumulation of Rab4 endosomes near the apical surface. These
phenotypes suggest that RhoGAP68F inhibits the scission and movement of Rab4 endosomes to the cell cortex. Rab4 localized preferentially with Fasciclin
III (FasIII), a component of septate junctions. Depletion of RhoGAP68F blocked epithelial elongation in part by blocking the rearrangement of the thick
pseudostratified epithelium to a thin simple epithelium. Our data suggest a role for Rho signaling cascades in regulating key trafficking itineraries of
junctional proteins. We propose that RhoGAP68F attenuates the recycling of cargo back to septate junction to decrease these adhesive cell-cell contacts to
facilitate epithelial flattening.
272B
crinkled
reveals a new role for Wingless signaling in Drosophila denticle formation.
Amy Bejsovec, Anna T. Chao. Dept of Biology, Duke University,
Durham, NC.
The specification of the body plan in vertebrates and invertebrates is controlled by a variety of cell signaling pathways, but how signaling output is
translated into morphogenesis is an ongoing question. We have discovered that genetic interactions between the Wingless (Wg) signaling pathway and a
nonmuscle myosin heavy chain, encoded by the
crinkled (ck)
locus play an important role in this process. In a screen for mutations that modify
wg
loss of
function phenotypes, we isolated multiple independent alleles of
ck
. These
ck
mutations dramatically alter the morphology of the hook-shaped denticles that
decorate the ventral surface of the
wg
mutant larval cuticle. In an otherwise wild-type background,
ck
mutations do not substantially alter denticle
morphology, suggesting a specific interaction with Wg-mediated aspects of epidermal patterning. Manipulating the level of Wg pathway activity changes the
structure of actin bundles during denticle formation in
ck
mutants. This Ck-dependent process is modulated by the activities of the Wg target gene,
shaven-
baby (svb)
, and of its transcriptional targets,
miniature (m)
and
forked (f)
. Using a temperature sensitive
wg
allele, we find that continued Wg activity is
required in
ck
mutants beyond 10 hours after egg-laying, the point at which Wg ceases to be required for patterning in a wild-type background. This suggests
that the
ck
mutant background reveals a late activity of Wg signaling in controlling
svb
expression levels. We propose that the the activity of the Ck
cytoplasmic myosin can somehow buffer the effects of misregulated Svb target gene products. We conclude that Ck acts in concert with Wg targets to
orchestrate the proper shaping of denticles in the Drosophila embryonic epidermis.
273C
Polarized secretion of Wnt/Wg in
Drosophila
wing imaginal discs.
Varun Chaudhary, Julia Gross, Michael Boutros. German Cancer Research Center
(DKFZ), Division Signaling and Functional Genomics and University of Heidelberg, Im Neuenheimer Feld 580, D-69120 Heidelberg, Germany.
Wnt/Wingless (Wg) are secreted glycoproteins that are required for variety of developmental processes, which are highly conserved from fly to human. In
Drosophila
wing imaginal discs Wg is secreted form the apical side of cells marking the dorso-ventral boundary. It is believed that Wg is then internalized
from the apical side, however a broader Wg gradient is also seen on the basolateral side of the disc. Whether this Wg gradient is generated through apical to
basolateral transcytosis and whether the apical secretion of Wg followed by its endocytosis is required for proper signaling has been unclear until now.
We are interested in understanding the mechanism of Wnt/Wg secretion and signaling. Through cell based RNAi screening, we have previously identified
proteins for example, Evenness interrupted and Opossum (p24), which are required for proper secretion of Wg. We are now interested in finding other