Basic HTML Version
Poster Full Abstracts - Cell Death
Poster board number is above title. The first author is the presenter
214
Loss of TBP function causes developmental arrest and apoptosis in Drosophila melanogaster.
Tun-Chieh Hsu, Chin Sern Yong, Ming-Tsan Su.
Department of Life Science-National Taiwan Normal University, Taipei, Taiwan.
TBP is a general transcription factor that is required for the transcription of virtually all genes in cells. Previous studies reported that inactivation of the
murine TBP gene by homologous recombination results in growth arrest and apoptosis at the embryonic blastocyst stages. Moreover, inhibition of TBP
expression by injecting antisense morpholino oligos causes developmental arrest and block of epiboly movements in zebrafish embryos at midblastula
stages. How TBP regulates animal development and its involvement in apoptosis are elusive. The main objective of my research is to investigate the role of
TBP in development and apoptosis. Additionally, it was reported that p53, a major pro-apoptotic regulator, interacted with TBP physically. We suspect that
TBP may suppress function of p53. Using genetics approach, we dissect the epistatic relationship of TBP and various apoptotic components, including diap1
and p53. In the future, we will also take biochemistry approach to exam if TBP modulates function of p53 directly.
307A
Genetic characterization of a Drosophila DUB involved in apoptosis.
Levente Kovács
1
, Olga Nagy
1
, Margit Pál
1
, Octavian Popescu
2
, Péter Deák
1
. 1)
Institute of Biochemistry, Hungarian Academy of Sciences Biological Research Centre, Szeged, Hungary; 2) Molecular Biology Center, Interdisciplinary
Research Institute on Bio-Nano-Sciences, Cluj-Napoca, Romania.
Removal of ubiquitin from poly-ubiquitylated proteins is performed by deubiquitylating enzymes (DUBs).Although the study of DUBs intensified in the
last few years, understanding of their functions remains considerably limited. Genetic analysis of mutant phenotypes in Drosophila melanogaster can provide
important information to elucidate the function of DUBs. From a genome-wide search using bioinformatics techniques, we identified 40 Drosophila genes
sharing high sequence homology with known human and yeast DUBs. Analyses of P element insertion mutants and/or transgenic RNA interference (RNAi)
knockdown lines suggest that the function of 24 of them is essential. These results can stimulate further functional studies of DUB genes in this model
organism. Ubiquitous knockdown of the CG12082 gene by RNAi causes early pupal lethality, accompanied with an increase in the number apoptotic cells in
the larval brain and imaginal discs. Eye specific induction of RNAi causes rough eye phenotype underlining apoptosis. Null alleles of CG12082 were
established by P element remobilization. The development of the homozygous null animals stops in L3 and they die in this stage after a 5 day long
stagnation. Acridine orange staining of L3 larval brains and wing discs revealed a very high incidence of apoptosis in these animals. In addition to this, the
expressions of reaper and hid, but not grim pro-apoptotic genes have been elevated in the CG12082 null mutant larval brains and imaginal discs. A
heterologous complementation experiment confirmed functional homology between CG12082 gene and yeast Ubp14. In addition to this, we also show that
free polyubiquitin chains accumulated in CG12082 mutants similarly to the yeast Ubp14 mutants that further support functional conservancy. Based on these
observations we conclude that the CG12082 gene encodes the Drosophila ortholog of the human Usp5 and yeast Ubp14 DUB enzymes, and it appears to be
involved in regulating apoptosis.
308B
Fzy/Cdc20 promotes neural stem cell survival.
Chaoyuan Kuang
1
, Cheng-Yu Lee
1,2,3,4
. 1) Cellular and Molecular Biology Graduate Program; 2)
Department of Cell and Developmental Biology; 3) Division of Molecular Medicine and Genetics, Department of Internal Medicine; 4) Center for Stem Cell
Biology, Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI 48109.
Premature loss of stem cells would perturb development and tissue homeostasis. However, cell survival is generally perceived as a passive process rather
than an integral component of the genetic program that maintains stem cell identity. Hence, specific mechanisms that maintain the viability of stem cells
in
vivo
remain completely unknown. Using neural stem cells (neuroblasts) in
Drosophila
larval brains as a genetic model system, we identified a novel
mutation in the
fizzy
(
fzy
) gene which results in premature loss of neuroblasts. This mutation (
fzy
G291R
) acts as a genetic null mutant allele of
fzy
, and leads to
the substitution of glycine 291 with arginine in the WD40 repeats of the Fzy protein. Neuroblasts in
fzy
G291R
mutant brains never express neuronal and glial
markers, and mosaic clones derived from single
fzy
G291R
mutant neuroblasts contain few post-mitotic cells but frequently lack the parental neuroblast.
Furthermore, distinct from neuroblasts experiencing mitotic catastrophe due to defective cytokinesis, neuroblasts in
fzy
G291R
mutant brains show loss of DNA
content, absence of activated Dronc caspase activity, and displayed morphological characteristics of necrosis. Fzy expression in the
fzy
G291R
mutant is
indistinguishable from the control and a
fzy
genomic rescue transgene restores neuroblasts in
fzy
G291R
mutant brains. Interestingly, in contrast to
fzy
null
intestinal stem cell and imaginal disc mosaic clones which are unable to proliferate,
fzy
G291R
clones show expansion and proliferation similar to wild type.
Together, these results indicate that
fzy
G291R
is capable of promoting normal cell cycle progression but is unable to maintain neuroblast survival. Additionally,
this work suggests that
fzy
functions to prevent neuroblast death specifically via a novel caspase-independent mechanism.
309C
Induction of IAP-antagonist and apoptosis in Drosophila and mosquito larvae following virus infection.
BO LIU
1
, JAMES BECNEL
2
, ROLLIE
CLEM
3
, LEI ZHOU
1
. 1) Dept. Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL; 2) United States
Department of Agriculture, ARS, Gainesville, FL; 3) Division of Biology, Kansas State University, Manhattan, KS.
Many vertebrate and insect viruses possess antiapoptotic genes that are required for their infectivity. This led to the hypothesis that apoptosis is an innate
immunoresponse important for limiting virus infections. The role of apoptosis may be especially important in insect antiviral defense because of the lack of
adaptive immunity. However, the cellular mechanism that elicits apoptosis in response to viral infection in insects was poorly understood. Our previous work
has demonstrated that the rapid induction of IAP-antagonists and apoptosis correlates with the resistance of mosquito larvae to CuniNPV infection (Liu et al,
Cell Death Differentiation. 2011). Using an in vivo infection system with the fall armyworm baculovirus AcMNPV (Autographa californica nuclear
polyhedrosis virus), we demonstrated that pro-apoptotic gene hid, not reaper, is induced in Drosophila larvae following injection of virus. This induction
happens within 1hr post virus injection (p.v.i.). By 2hr p.v.i., the level of hid mRNA had returned to the same level as control. Further characterization of the
cellular identity of viral infection-induced apoptotic response will be reported. We believe that establishing of this AcMNPV infection system in Drosophila
will allow us to use the genetic resources that are uniquely available in Drosophila to study the signaling pathways responsible for viral infection-induced
apoptosis. Moreover, this experimental system will allow us to test the role of apoptosis as an innate immunoresponse to limit viral infection in insects.
310A