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Poster Full Abstracts - Cell Death
Poster board number is above title. The first author is the presenter
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interact with other proteins involved in spindle assembly. We have isolated 18 EMS induced mutations in a screen, which induce synthetic lethality in a
homozygous sub mutant background. These mutations may identify new genes involved in spindle assembly and microtubule organization especially in
meiotic spindle assembly which is not well understood. The screen yielded mutations in at least 6 different genes, we are still testing the rest by
complementation. Of the mutations, 3 were alleles of
Incenp
and 2 of
ial
. There were previously no alleles available for
ial
in Drosophila. Two other
mutations
22.64
and
15.173
, both with 2 alleles, map to narrow intervals on the second chromosome containing 10 and 17 genes respectively. Both these
mutations are homozygous lethal and hence in essential genes. We will characterize the role of these mutations and their interactions with
subito
in mitotic
and meiotic spindle assembly.
327C
The Regulation of Microtubule Dynamics is Essential for Meiotic Spindle Organization in Drosophila Females.
Sarah Radford, Andrew Harrison, Kim
McKim. Waksman Institute, Rutgers University, Piscataway, NJ.
Inaccurate chromosome segregation during oogenesis is a leading cause of spontaneous abortion and birth defects in humans. Proper chromosome
segregation is achieved through the interaction of chromosomes with a bipolar array of microtubules that constitute the meiotic spindle. The meiotic spindle
in the oocytes of many organisms, including humans and Drosophila, is built in the absence of the classical microtubule-organizing centers known as
centrosomes. In the absence of centrosomes, the cues controlling spindle organization remain unknown. In addition, microtubules are inherently dynamic;
therefore, we hypothesized that the regulation of microtubule dynamics plays an important role in the organization of the meiotic spindle. Because many of
the proteins involved in the regulation of microtubule dynamics are essential for development, much of our work has been made possible by the germline-
specific RNAi technology generated by the Transgenic RNAi Project. We have shown that a member of the kinesin-13 family of microtubule-
depolymerizing enzymes, KLP10A, is required for the control of meiotic spindle organization, microtubule length, and chromosome orientation. We have
also shown that a second kinesin-13, KLP59D, is not required in meiosis and, surprisingly, is not essential for development. Investigation into the third
Drosophila kinesin-13, KLP59C, is ongoing. We have also shown that the Drosophila CLASP homolog, Orbit/MAST, partly antagonizes KLP10A activity,
suggesting that meiotic spindle organization results from a balance of microtubule dynamics. We are currently investigating several other proteins involved
in the regulation of microtubule dynamics, including Patronin and Sentin, to gain further insight into how the regulation of microtubule dynamics contributes
to the formation of a functional meiotic spindle. Our results thus far show that the regulation of microtubule dynamics is critical for the generation of a
meiotic spindle with the capacity to effect accurate chromosome segregation.
328A
The Hippo Pathway targets the Cdh1/fzr inhibitor Rae1 to regulate mitosis and establish organ size homeostasis.
Maryam Jahanshahi
1
, Kuangfu
Hsiao
2
, Andreas Jenny
3
, Cathie Pfleger
1
. 1) Department of Oncological Sciences, Mount Sinai School of Medicine, New York, NY; 2) Department of
Neuroscience, Mount Sinai School of Medicine, New York, NY; 3) Department of Developmental and Molecular Biology, Albert Einstein College of
Medicine, Bronx, NY.
The Hippo Tumor Suppressor pathway serves as a master regulatory axis which coordinates proliferation, growth, and apoptosis to establish and maintain
appropriate organ size. It is well established that loss of pathway components promotes cell division, cell death resistance, and tumor-like overgrowth in both
Drosophila and vertebrates. However, the mechanisms by which the pathway effects normal tissue homeostasis remain less well-understood. Typically,
organ homeostasis engages mechanisms to ensure that variations in proliferation do not alter organ size. Thus, how the pathway integrates restricting
proliferation and activating an “organ size checkpoint” remains a major unanswered question. We have identified the Cdh1-inhibitor Rae1 at the nexus
within the Hippo Pathway integrating proliferation and organ size. Exogenous Rae1 increases both cell proliferation and organ size. Rae1 is required in vivo
for S-phase entry and mitotic progression and is phosphorylated and degraded upon activation of Hippo signaling. We propose a model that Hippo signaling
promotes Cdh1-Anaphase Promoting Complex/Cyclosome activity by relieving its Rae1-mediated inhibition. Importantly, Rae1 reduction compromises
survival of Hippo-deficient tissue indicating synthetic lethality and a requirement for Rae1 reminiscent of oncogene/non-oncogene “addiction”.
329B
Translationally Controlled Tumour Protein (TCTP) regulates 14.3.3s function during
Drosophila
organ development.
Phuong Thao Le. KAIST,
Daejeon, South Korea.
Translationally controlled tumour protein (TCTP) has drawn interests because of its potential roles in tumorigenesis. Our previous study has shown that
Drosophila
TCTP (dTCTP) is essential for organ growth by acting through Rheb GTPase in TOR signaling. However, evidence suggests that dTCTP
interacts with additional signaling components. By genetic modifier screening, we have identified
14-3-3ε
and
14-3-3ζ
as potential candidate genes that
interact with
TCTP
. Here we present analysis of these genetic interactions in
Drosophila
organ development. Reduced levels of either form of 14-3-3
proteins led to strong enhancement of the small eye/wing phenotype resulting from TCTP RNA interference (RNAi). In addition, TCTP co-localizes with
14-3-3 in different tissues. We also show that 14-3-3 proteins interact with other TOR signaling components like Rheb and TSC1/2 in controlling the organ
growth. 14-3-3 proteins are known to bind to TSC2 at multiple, phosphorylated sites, and negatively regulate TSC1/2 function. In TSC-TOR pathway, TCTP
acts antagonistically to TSC1/2. There is possibility that TCTP affects 14-3-3s and restricts the TSC1/2 activity to control organ growth. Our data suggest
that TCTP is required for stabilizing 14-3-3s, thereby inhibiting the TSC complex function. This research provides new insights into the function of dTCTP
in growth regulation.
330C
uninflatable
and
Matrix metalloproteinase 1
are required for tissue specific growth in the larval trachea of
Drosophila melanogaster
.
Paulo Leal,
Joshua Neff, Robert Ward. Molecular Biosciences, University of Kansas, Lawrence, KS.
Post-embryonic growth in
Drosophila
is tied to nutrition through the Insulin receptor phosphoinositide-3-kinase - Target of Rapamycin (InR/PI3K - TOR)
signaling pathway. Yet specific organs show variable growth rates suggesting that organs and tissues can independently regulate growth. To identify
mechanisms of tissue specific growth, we are taking a genetic approach to identify mutations that specifically alter trachea size relative to overall body size.
The larval trachea system of
Drosophila
is well suited for this study as the trachea is a branched tubular organ required for gas exchange that expands