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Poster Full Abstracts - Gametogenesis and Organogenesis
Poster board number is above title. The first author is the presenter
282
Zfrp8 and Dlg5.
562A
Investigation of Snail family proteins in cell death during
Drosophila
oogenesis.
Victoria Kathryn Jenkins, Kim McCall. Department of Biology, Boston
University, Boston, MA.
In organisms including
C. elegans
and mammals, members of the Snail family of transcription factors are responsible for aspects of cell death, the
epithelial-to-mesenchymal transition, and cell cycle regulation; however, it is unknown whether they play a role in
Drosophila
cell death. During a screen
for cell death genes in the ovary, we identified the Snail family member
escargot
as a possible regulator of cell death. The nurse cells (NCs) of egg chambers
can undergo two naturally occurring death events. Starvation-induced death (“mid-stage”) can be induced halfway through oogenesis, whereas
developmental death (“late-stage”) occurs near the end of egg maturation. Overexpression of the Snail family gene
escargot
prevented both mid- and late-
stage death of the nurse cells, and disrupted other aspects of normal egg chamber development. This phenotype is suppressed by overexpression of the
caspase gene
dcp-1
in mid-stage death, suggesting that
escargot
acts upstream of or in parallel to
dcp-1
. Additionally, since Escargot cannot suppress the
phenotype of
dcp-1
driven by a UASp promoter, it may be a transcriptional repressor of
dcp-1
. The
escargot
overexpression phenotype mimics the effect of
blocking caspases and of overexpressing the inhibitor of apoptosis protein DIAP-1. Therefore, either the Snail proteins are a part of normal nurse cell death,
or when highly expressed, are capable of regulating a component of the cell death pathways which cause these phenotypes. In the future, we will analyze
loss-of-function mutants to determine whether Snail family members have a role in normal cell death during oogenesis. Current progress will be presented.
563B
The Diverse Function of PAPI, a Tudor-Domain-Containing Interactor of PIWI Proteins, in Oogenesis and Embryogenesis.
Li Liu, Na Liu, Sneha
Mani, Haifan Lin. Yale University, New Haven, CT.
Drosophila Piwi proteins, Piwi, Aub (Aubergine) and Ago3 (Argonaute3), bind to Piwi-interacting RNAs (piRNAs) and function in epigenetic regulation
and transposon control. We previously identified a novel Piwi-interacting protein, Papi, which binds symmetrically dimethylated arginine residues (DMAs)
in Piwi proteins through its Tudor domain. Papi recruits Ago3 to the nauge and forms a complex with Ago3, Me31b and Trailer Hitch (Tral) to regulate
transposition. Here we report a loss-of-function allele of papi that causes female sterility. papi, ago3 and tral mutants exhibit delays in oocyte determination
and defects in oocyte polarity and embryonic axis formation, which are commonly observed in other nuage component mutants. The microtubule minus end-
directed motor, dynein, is mislocalized in papi, ago3 and tral mutant ovaries, suggesting the microtubule-dependent transport is defective in these mutants.
Moreover, ago3 and papi mutant embryos exhibit drastic defects in germline and somatic cell lineages, indicating that the Ago3 and Papi are involved in
germline determination and mitosis during early embryogenesis. However, piRNA production is not significantly altered in papi mutant, suggesting that the
Papi/Ago3 complex exerts its function in oogenesis and early embryogenesis independent of piRNA biogenesis pathway.
564C
Wnt4 regulates germline follicle formation.
Lucy Morris, Joan Pulupa, Allan Spradling. Carnegie Institution, Baltimore, MD.
Germline follicle formation occurs when germ cells discard their covering of somatic escort cells and simultaneously recruit a wrapping of somatic follicle
cells. Follicle cells are generated by division of follicle stem cells and subsequently direct formation of a mature egg. We found that Wnt4, a gene required
for oogenesis in mouse, also regulates follicle formation in Drosophila. Wnt4 is produced by escort cells and acts both autonomously and on neighboring
follicle cells. Using live imaging of follicle formation in mutant ovaries we have shown that Wnt4 regulates cell proliferation and not migration, its
documented role in other tissues. The simple architecture of the Drosophila ovary combined with our ability to carry out live imaging with single cell
resolution will enable us to use Wnt4 action on follicle formation to model how Wnts exert profound organizing activity on epithelial cells and during
embryonic development.
565A
The Role of Translational Regulation in Meiotic Chromosome Segregation in Oocytes.
James G. Ruggero, Sarah J. Radford, Kim S. McKim. Genetics,
Waksman Institute of Microbiology, Rutgers, Piscataway, NJ.
A developing oocyte accumulates materials, such as nutrients, proteins and transcripts, from surrounding nurse cells. Concurrently, the oocyte undergoes
meiosis. We performed a screen to find chromosome segregation-defective mutants that may be homozygous sterile or lethal, which are common for
developmental and meiotic mutants. One of the proteins responsible for microtubule spindle formation during meiosis is Subito, a kinesin-6 protein required
for bundling interpolar microtubules. Null mutants of
subito
(
sub
) are sterile due to a defect in pronuclear fusion. We identified a new mutation,
sub
4034
, that
is fertile, but shows high levels of nondisjunction (11%, n=1160). In addition, nondisjunction is elevated in
sub
4034
heterozygous in combination with
deficiencies in several regions. This evidence directed us to perform a screen to identify mutations that dominantly interact with
sub
4034
. We found nine
mutants from this screen. Mapping, sequencing and successful rescue with a wild-type transgene identified one mutation in
maternal expression at 31B
(
me31B
) with 12% nondisjunction (n=620) in the
sub
4034
heterozygous background. Me31B mediates translational silencing. Thus, loss of
me31B
causes
premature translation of oocyte-localizing proteins. This suggests that translational suppression may be important for chromosome segregation. Previous
analysis of spindle formation in
me31B
-null mutants has not occurred because oocytes fail to develop to maturity. While
me31
2212
mutants are mostly
inviable, we were able to examine germline clones of
me31B
2212
to test if the translation of meiotic proteins is affected. Immunocytochemistry of
me31B
2212
germline clones showed wildtype spindle formation in both oocytes and embryos and expression of
sub
. We are lacking evidence that Me31B regulates
sub
.
Testing for a more severe interaction is underway. We also plan to test other genes involved in translational suppression for an interaction with
sub
4034
. From
the identification of the interaction of
me31B
2212
with
sub
4034
, we have found a link between development and meiosis.
566B
PI4KIIIα is required for cortical integrity and cell polarity during
Drosophila
oogenesis.
Julie Tan
1,2
, Jason Burgess
1,2
, Karen Oh
3,4
, David Hipfner
3,4
,
Julie Brill
1,2
. 1) Program in Cell Biology, Hosp Sick Children, Toronto, ON, Canada; 2) Dept of Molecular Genetics, University of Toronto, Toronto, ON,
Canada; 3) Epithelial Cell Biology, Institut de Recherches Cliniques de Montreal, Montreal, QC, Canada; 4) Department of Medicine, University of