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Poster Full Abstracts - Cell Biology and Signal Transduction
Poster board number is above title. The first author is the presenter
200
254B
Steroid-induced microRNA let-7 acts as a spatio-temporal code for neuronal cell fate in Drosophila learning centers.
Mariya M. Kucherenko, Halyna
R. Shcherbata. Gene expression and signaling, Max Planck Institute for biophysical chemistry, Goettingen, Germany.
One of the key characteristics of neural progenitors is their ability to produce multiple neuron types in the course of an individual’s development.
Specialized neurons derive at specific times, suggesting that temporal codes act together with lineage neuronal cell fate determinants. Hormones are great
candidates for this type of regulation, since they are systemic factors that regulate all major developmental steps. Intriguingly, neuroblasts in mushroom
bodies continue to divide after all other neuroblasts have ceased their division and similar to mammalian neural progenitors have the capacity to generate
many closely related neurons. We show that in the post-embryonic Drosophila brain, steroids act as temporal cues, which specify cell fate determination of
mushroom body neuroblast progeny. Chronological regulation of neurogenesis additionally is refined by miRNA let-7, absence of which causes
morphological and physiological defects, leading to learning and memory impediment. let-7 is expressed in response to developmentally regulated steroid
pulses to modulate levels of cell adhesion molecules in differentiating neurons via the transcription factor Abrupt and possibly JAK/STAT cytokine
signaling. The differential adhesion hypothesis explains how neurons that express different levels of cell adhesion proteins cluster together and form
complex internal brain structures. Taken together, our data show that miRNA let-7 is a steroid hormone-dependent cell fate determinant acting as a temporal
code along with spatially controlled lineage cues to specify neuronal cell fate via regulation of cell adhesion. Identifying the modulators of temporal codes
and the mechanisms of their actions will help to understand how neuronal multiplicity takes place and aid in overcoming age-related obstacles of
regenerative therapies that attempt directed neurogenesis.
255C
ULTImate Yeast Two-Hybrid: From High Quality Protein Interaction Mapping to Single Chain Antibody Analysis.
Philippe le Clerc
1
, Stephanie
Miserey-Lenkei
2
, Ole Vielemeyer
2
, Petra Tafelmeyer
1
, Franck Perez
2
, Arnaud Echard
2,3
, Bruno Goud
2
, Jacques Camonis
2
, Etienne Formstecher
1
, Jean-
Christophe Rain
1
. 1) Hybrigenics Services SAS, Paris, France; 2) Institut Curie, Paris, France; 3) Institut Pasteur, Paris, France.
Protein interaction mapping has proven instrumental for the understanding of signaling pathways in Homo sapiens, Drosophila melanogaster and other
model organisms. We have published a Drosophila protein interaction map centered on cancer-related and signaling proteins (http://pim.hybrigenics.com/).
These data were obtained using a yeast two-hybrid (Y2H)-based technology and a highly complex D. melanogaster embryo cDNA library. We have now
applied our domain-based strategy to construct four new high-complexity, random-primed D. melanogaster cDNA libraries from adult head, ovaries, 3rd
instar larvae and larvae brain. These libraries are accessible on a fee-for-service basis and will allow deepening the understanding of molecular pathways in
Drosophila. Here we illustrate our approach with results obtained in an exhaustive Y2H screen using active Drosophila Rab6 (Q71L) as bait against our
Drosophila embryo cDNA library. We identified zipper, the Drosophila non-muscle myosin II heavy chain gene as prey and show evidence for the role of
this interaction in vesicle biogenesis and transport. We further characterized using the Y2H technique a conformation-specific antibody selected against
human Rab6 (scFv AA2) that exclusively binds the activated form of the protein. For this purpose, we screened our cDNA libraries from human placenta
and Drosophila embryos with AA2 as bait. In both screens Rab6 was identified, indicating that the antibody selected against the human protein can also
recognize the fly Rab6. Only fragments mostly spanning the entire ORF of Rab6 were found, very likely because the entire core region of Rab6 had to be
expressed to allow the binding of this conformation specific antibody. Interestingly, AA2 was also able to act as intrabody, as shown by labeling of Golgi
stacks in living Drosophila S2 cells.
256A
Patterning the Drosophila eggshell along two axes by the glypican Dally.
David J. Lemon
1
, Nir Yakoby
1,2
. 1) Biology Department, Rutgers University,
Camden, NJ; 2) Center for Computational and Integrative Biology, Rutgers University, Camden, NJ.
Heparin sulfate proteoglycans (HSPGs) participate in the regulation of numerous cell signaling pathways in tissues throughout animal development. In
Drosophila melanogaster, the HSPG Division abnormally delayed (Dally) acts as a co-receptor in several signaling pathways, including bone morphogenetic
protein (BMP) signaling, during imaginal wing disc development. During oogenesis, we found that
dally
is patterned in the follicle cells (FCs), a mono-layer
of epithelial cells which surround the oocyte. This pattern is evolutionary conserved across species, and spatially overlaps the BMP signaling domain, which
was monitored by phosphorylated-MAD (P-MAD). Using genetic perturbations, we determined that, in the FCs,
dally
is a downstream target of BMP
signaling. Furthermore, in clones of cells null for
dally
, P-MAD was lost cell autonomously. Another critical regulator of egg development is the epidermal
growth factor receptor (EGFR) signaling pathway. It was reported that ectopic expression of a similar HSPG, Dally-like protein (Dlp), modified the EGFR
activation by changing the TGF-α like ligand Gurken (GRK) distribution. Overexpression of
dally
had no effect on eggshell patterning; however, depletion
of
dally
gives rise to deformed eggshell structures due to the disruption of EGFR activation gradient. Notably, the two dorsal appendages (DAs), the
embryo’s respirators, were fused. This phenotype is consistent with reduction in EGFR activation. Furthermore, in these perturbations, we found a reduced
operculum size, which reflects reduction in levels of BMP signaling. Based upon our results, we propose a model by which Dally contributes to eggshell
patterning along the anterior-posterior and dorsal-ventral axes by regulating the BMP and EGFR signaling pathways, respectively.
257B
New roles for the Elmo-Moleskin complex in muscle-tendon attachment.
Ze (Cindy) Liu, Erika R. Geisbrecht. School of Biological Science , University
of Missouri-Kansas City, Kansas City , MO.
The Mbc-Elmo signaling pathway is highly conserved from C. elegans to vertebrates and is essential for many developmental processes, including
phagocytosis and cell migration. Flies that possess mutations in the elmo/ced12 locus are lethal and exhibit defects in myoblast fusion, thorax closure, and
border cell migration. Herein, using mass spectrometry approaches to identify new players in the Elmo signaling pathway, we uncovered Drosophila
Importin-7 (Dim-7), or Moleskin (Msk) as a potential Elmo-interacting protein. While the canonical role of Msk is in nuclear import, we recently uncovered
a new function for Msk in late myogenesis. We showed that Msk is enriched at muscle attachment sites and msk mutant embryos exhibit muscle attachment
defects. Many known components of the muscle-tendon attachment sites are properly localized in msk mutant embryos, including the integrins, integrin
associated proteins, and extracellular matrix proteins. However, the tendon cell differentiation factor Stripe and activated MAPK, are missing from the