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Poster Full Abstracts - Cell Biology and Signal Transduction
Poster board number is above title. The first author is the presenter
179
Genes & Development Graduate Program, UT GSBS, UTMDACC, Houston, TX; 3) Fachbereich Biologie, Philipps-Universitat Marburg, Germany.
Wound healing is essential for the comfort and survival of most organisms. Epidermal closure requires that cells can recognize tissue damage, alter their
behavior to migrate across the gap, and eventually reestablish tissue continuity. Two signaling pathways are known to regulate these behaviors in
Drosophila
larvae, the Jun N-terminal kinase (JNK) signaling pathway and the receptor tyrosine kinase, Pvr. Currently, it is uncertain how these signaling pathways
regulate the actin cytoskeletal rearrangements that are a prerequisite for efficient cell migration. Here we show that
chickadee
, the
Drosophila
Profilin, is
necessary for larval wound closure. After wounding, Profilin protein levels increase in cells around the wound gap. This increase is likely a result of the
transcriptional activation of the chic locus. We show here that wound-induced chic transcription is regulated by the JNK signaling pathway, and not by Pvr.
The canonical JNK pathway has two downstream transcription factors, Jun and Fos, but of these, only Fos regulates chic transcription. Lastly, we also show
that larvae lacking epidermal Profilin are unable to properly concentrate actin at the wound edge and are unable to extend filopodia and lamellipodia into the
wound area. Thus, we show a connection between JNK signaling pathway activation and expression and function of an important cytoskeletal regulator
during wound closure.
171C
Cytoskeletal polarization during collective cell migration in the Drosophila egg chamber.
Maureen P. Cetera, Sally Horne-Badovinac. DRSB,
University of Chicago, Chicago, IL.
Collective cell migration is critical for proper morphogenesis of developing organisms. The Drosophila egg chamber provides a novel system in which to
study collective cell migration of a continuous epithelial cell layer. During oogenesis, the egg chamber elongates from a spherical precursor to a mature
elliptical egg. At this time, the follicular epithelium migrates circumferentially around the egg chamber’s anterior-posterior axis along an extracellular
matrix. Follicle cell migration is hypothesized to contribute to egg chamber elongation but the molecular mechanisms underlying this morphogenetic event
are currently unknown (Haigo and Bilder, 2011). We predict the migrating epithelium would require planar polarization of its cytoskeleton and we have
shown each follicle cell has a distinct leading and trailing edge. The leading edge consists of actin-based protrusions that are sensitive to Integrin and
Enabled levels and the back of the cell displays Myosin II accumulation that may serve to relieve focal adhesions to allow forward migration. We have
developed techniques to observe the dynamics of follicle cell crawling along the extracellular matrix and by manipulating protrusion formation, adhesion or
Myosin II activity, we can determine their role in collective cell migration of the follicular epithelium.
172A
Distinguishing spectrin gain-of-function and loss-of-function effects in the larval fat body of Drosophila.
Bianca Diaconesea, Ron Dubreuil. Dept. of
Biological Sciences, University of Illinois Chicago, Chicago, IL.
Lethal mutations affecting α and β spectrin have been described in many different systems. Phenotypes have also been observed with overexpression of
full-length β spectrin or spectrin fragments in model systems. The latter phenotypes are often categorized as dominant negatives, although this can be
difficult to demonstrate directly. Here we gain new insight into this issue by comparing the effects of β spectrin overexpression and knockdown in a single
cell type. We find: 1) RNAi knockdown of α or β spectrin in the larval fat body of
Drosophila melanogaster
altered plasma membrane morphology, but did
not otherwise affect growth or viability of the organism. 2) β spectrin overexpression was lethal at the highest levels and produced milder phenotypes at
lower levels. In contrast, overexpression of α spectrin was never lethal. 3) Excess β spectrin accumulated specifically at the plasma membrane, resulting in
an apparent block in lipophorin secretion from the fat body. This block led to abnormal dietary lipid accumulation in the midgut, identical to that observed
with lipophorin RNAi. 4) Lethality and lipid transport defects were overcome when α spectrin was co-expressed with β spectrin. Rescue did not noticeably
change the abundance or distribution of overexpressed spectrin, suggesting that the β phenotype depends upon misregulation of β spectrin function in the
absence of α, as well as overexpression. There are a number of implications of this work for assessing spectrin function. While there are some dominant
negative effects of β overexpression in the fat body, there also appear to be hypermorphic gain-of-function effects that may not be related to normal spectrin
function (e.g. on secretion of lipophorin). We speculate that gain of function effects could play a prominent role in spectrin genetics in other systems as well.
173B
The Putative Ena Interacting Protein, SKIP, is Required for Border Cell Migration.
Julie Gates, Kate Bowen, Lindsay Regruto, Kara Weichler.
Biology Dept., Bucknell University, Lewisburg, PA.
During development the actin cytoskeleton must be remodeled to accommodate the remarkable changes in cell shape, cell rearrangements and cell
migrations that occur as tissues and organs are formed. If actin dynamics are not properly regulated, morphogenesis is disrupted and normal development
fails. Numerous proteins have been identified that influence actin dynamics including members of the Ena/VASP protein family.
Drosophila
has a single
Ena/VASP family member, Ena. Previous work has shown that Ena is required during multiple morphogenetic processes including dorsal closure, nurse cell
dumping and border cell migration. To gain additional insight in to how Ena may be regulated, we have chosen to examine the role of a putative Ena binding
partner, SKIP (Shal K
+
Channel Interacting Protein). SKIP was found to bind to Ena in a large-scale yeast two-hybrid screen carried out by Giot and
colleagues in 2003. There are three SKIP protein isoforms. The longest isoform, SKIP1, contains an N- and C-terminal SAM (sterile-alpha-motif) domain
and an SH3 domain. While we are currently carrying out biochemical experiments to verify this interaction, the presence of an SH3 domain in SKIP1 and
SKIP2, and a proline-rich region in Ena that has been shown to bind SH3-containing proteins, made SKIP a putative binding partner worth further
characterization. We have used tissue-specific expression of SKIP RNAi to reduce SKIP protein levels in either all somatic follicle cells (T155-Gal4) or
specifically in border cells, centripetal and posterior follicle cells (slbo-Gal4). In both cases a reduction in SKIP protein levels results in delayed border cell
migration and the occasional failure of a subset of border cells to remain within the border cell cluster. Preliminary data suggests that the reduction in SKIP
protein levels may also result in defects in the follicle cell basal actin network. We are currently examining the localization of Ena in follicle cells with
reduced SKIP protein levels to determine whether SKIP functions by regulating the localization of Ena.
174C
Narrowing regions of chromosome two that genetically interact with Abl kinase during embryonic development.
Terri Hale
1
, Daniella Kawa
1
, Adam
O-Neil
1
, April Peterson
1
, Andrew Simmons
1
, Traci Stevens
2
. 1) Cosby High School, Midlothian, VA; 2) Biology Dept, Randolph-Macon College, Ashland,