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Poster Full Abstracts - Cell Biology and Signal Transduction
Poster board number is above title. The first author is the presenter
201
tendon cells. Rescue experiments demonstrate that Msk is required in the muscle cells to influence tendon cell markers. Furthermore, we can rescue the
muscle detachment phenotype in msk mutants upon reintroduction of the muscle-secreted tendon signaling factor Vein or by expressing an activated form of
MAPK in the tendon cells. The above data support a model whereby Msk functions in the muscle cells to modulate the activity of the Vein-EGFR signaling
pathway essential for tendon cell differentiation and subsequent MTJ formation. We will present studies focused on establishing how the Elmo-Msk
complex functions in the formation and maintenance of the embryonic muscle-tendon attachment sites. Our preliminary data suggests that the msk muscle
detachment phenotype is enhanced by mutations in elmo.
258C
Characterizing the role of a novel gene in the regulation Fat signaling in
Drosophila
.
Robyn Rosenfeld
1,2
, Helen McNeill
1,2
. 1) Samuel Lunenfeld
Research Institute, Mount Sinai Hospital, Toronto, ON, Canada; 2) Molecular Genetics, University of Toronto, Toronto, ON, Canada.
Fat is a large cadherin that plays a role in both tissue growth and planar cell polarity (PCP). How Fat regulates these cellular processes is not fully
understood. Fat’s involvement in tissue growth is through the Hippo (Hpo) kinase pathway, which has an important role in proliferation, apoptosis and the
control of organ size in both
Drosophila
and mammals. A yeast two-hybrid screen conducted in the laboratory identified proteins that can bind the
cytoplasmic domain of Fat, providing candidates for mediators of Fat-dependent growth and PCP. Using the available genome-wide RNAi libraries of
transgenic flies, we knocked down the function of each gene identified through the screen in the
Drosophila
eye. Through analysis of adult eye size and
shape and photoreceptor organization, a gene has been identified that when disrupted, phenocopies the specific overgrowth effects that are indicative of Hpo
pathway mutations in the eye. This gene is uncharacterized and is conceptually translated into a multi-pass transmembrane protein of 450 amino acids with a
conserved domain of unknown function. These findings suggest that this protein is working with Fat to regulate the Hpo pathway. We have generated a null
allele through ends out gene targeting and homozygous mutant flies display male sterility and lethality phenotypes. We are currently examining the potential
role this novel gene plays in Fat signaling.
259A
Dissection of an ecdysone-inducible type II transmembrane serine protease-signaling pathway in imaginal discs.
Sienna M. Sartori, Cynthia Bayer,
Laurence von Kalm. Department of Biology and Biomolecular Sciences Center, University of Central Florida, Orlando, FL.
The ecdysone-inducible Stubble-stubbloid (Sb-sbd) locus encodes a type II transmembrane serine protease (TTSP) required for imaginal disc and bristle
morphogenesis. Extracellular Sb-sbd proteolytic activity modulates intracellular Rho1 signaling in leg and wing imaginal discs via an unknown outside-in
signaling mechanism. Understanding this mechanism is of interest because signaling by vertebrate TTSPs is linked to a number of human pathologies. We
have adopted multiple strategies to identify genes involved in this signaling process. A genetic screen identified the Notopleural (Np) locus as an enhancer of
Sb-sbd with respect to imaginal disc morphogenesis. Np encodes a serine protease and is induced by ecdysone in leg imaginal discs. Our data indicate that
Np acts downstream of Sb-sbd, raising the possibility of a proteolytic cascade/network leading to activation of Rho1. Additional strategies to identify
components of the signaling pathway include analysis of deficiencies that interact with Sb-sbd and Np, and testing genes that are co-expressed with Sb-sbd
and Np in imaginal discs, such as candidate cell-surface receptors that might be targets of the Sb-sbd or Np proteases.
260B
MAP3K molecular chimeras for the study of jun kinase pathway signaling specificity.
Beth Stronach. Dept Micro & Mol Genetics, Univ Pittsburgh Sch
Medicine, Pittsburgh, PA.
A highly diverse set of protein kinases function as early responders in the mitogen- and stress-activated protein kinase (MAPK/SAPK) signaling pathways.
For instance, humans possess at least fourteen MAP3K protein kinases that activate Jun Kinase (JNK). To develop specific therapeutic interventions for
human diseases linked to dysfunctional JNK signaling, a major challenge is to decipher the selective functions of these upstream kinases. In Drosophila,
there are seven MAP3K family members, a few of which have been implicated, singly or in combination, in JNK-dependent stress response and
development. To test whether MAP3Ks might substitute for each other and to identify protein domains that could instill selective function, we generated
molecular chimeras between two MAP3K family members, Slpr and Tak1, which share 32% identity (53% sim) across the kinase domain, but otherwise do
not resemble each other in domain structure or sequence. They have at least one substrate in common, the JNK kinase Hep, and activate JNK signaling in
various contexts. If one key function of these proteins is to phosphorylate and activate Hep, then it follows that their kinase domains may functionally
compensate for one another. We found that although the Tak1 kinase domain replacement in Slpr was sufficient to activate JNK signaling during dorsal
closure, it did not compensate for wildtype Slpr in promoting adult viability, suggesting that there is intrinsic specificity of the catalytic domains, despite
having the same substrate. Also, though the C-terminus of Slpr is not essential for viability, it promotes cortical enrichment of the protein. Swapping the C-
terminus of Tak1 for that of Slpr did not restore proper localization, but it did not impede Slpr-dependent JNK signaling during dorsal closure. Moreover, the
Tak1 C-terminus allowed the integration of chimeric proteins into a Tak1-dependent pathway downstream of Egr, a property not shared with Slpr. These
results suggest that the selective deployment of a particular MAP3K can in part be attributed to their intrinsic sequence differences.
261C
Regulation of Hippo signaling by Jun kinase signaling during Drosophila wing discs regeneration and in neoplastic tumors.
Gongping Sun, Kenneth
Irvine. Waksman Institute of Microbiology, Rutgers, the State University of New Jersey, Piscataway, NJ.
When cells undergo apoptosis, they can stimulate the proliferation of nearby cells, a process referred to as compensatory cell proliferation. The stimulation
of proliferation in response to tissue damage or removal is also central to epimorphic regeneration. The Hippo signaling pathway has emerged as an
important regulator of growth during normal development and oncogenesis from Drosophila to humans. Our study focused on the role and regulation of
Hippo pathway in compensatory proliferation and regeneration in Drosophila wing imaginal discs after disruption of epithelia. We found that induction of
apoptosis in the Drosophila wing imaginal disc stimulates activation of the Hippo pathway transcription factor Yorkie in surviving and nearby cells, and that
Yorkie is required for the ability of the wing to regenerate after genetic ablation of the wing primordia. Induction of apoptosis activates Yorkie through Jun
kinase pathway, an important regulator in apoptosis and regeneration, and direct activation of Jun kinase signaling also promotes Yorkie activation in the
wing disc. Our results also showed that depletion of neoplastic tumor suppressor genes, including lethal giant larvae and discs large, or activation of aPKC,