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Poster Full Abstracts - Gametogenesis and Organogenesis
Poster board number is above title. The first author is the presenter
284
we have analyzed genes required for these processes in tracheal terminal cells. Terminal cells, a component of the respiratory system, undergo two distinct
morphogenetic processes: subcellular branching morphogenesis, and subcellular apical lumen formation. In previous work, we showed that both branching
and lumen morphogenesis are regulated by components of the PAR-polarity complex, and that this complex is downstream of FGF signaling, a known
regulator of terminal cell branching and outgrowth. Our recent work has turned to investigating the role of vesicle trafficking pathways in branching and
tubulogenesis, focusing on the exocyst complex. The exocyst is an octomeric complex composed of Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and
Exo84, and is most commonly known for its role in directing vesicles to specific locations on the plasma membrane to facilitate exocytosis and cell growth.
We find that in general all components of the exocyst complex are required for terminal cell branching, but only a subset are required for lumenongenesis. In
particular, we find that exocyst members Exo84 and Sec15 are required for both branching and lumenogenesis in terminal cells. In contrast, we find Exo70 is
required for subcellular branching but not lumen formation. These data suggest that individual members of the exocyst play two roles in terminal cell
morphogenesis: one in which the exocyst is required for exocystosis and branching at the growing terminal tip, and another in which only specific complex
members associated with vesicles are required for a tubulogenesis program.
571A
Tramtrack69 Regulates Gene Expression During Tube Morphogenesis in the
Drosophila
Ovary.
Nathaniel C. Peters, Celeste A. Berg. Deptartment of
Genome Sciences and the Molecular and Cellular Biology Program, University of Washington, Seattle, WA.
During late
Drosophila
oogenesis, the follicular epithelium that surrounds the oocyte instructs two dorsal groups of cells to undergo morphogenesis and
form tubular molds for the respiratory filaments of the eggshell, the dorsal appendages (DAs). DA tubulogenesis is a simple and genetically accessible model
for studying the poorly understood process of epithelial tube formation, providing insight into how an epithelium transitions from patterning to coordinated
cell shape change. The Tramtrack69 transcription factor has essential roles throughout fly development; the
twin peaks
mutation is a
tramtrack
hypomorph
that reduces TTK69 levels during late oogenesis. It causes shortened DAs by disrupting follicle cell shape and migration during DA tube expansion.
Microarray analysis of wild type and
twin peaks
ovaries suggests that TTK69 influences a wide range of genes, from other transcription factors to regulators
of the cytoskeleton, cell migration, axon guidance, and hormone processing. Array verification via
in situ
hybridization revealed that
paxillin
, a regulator of
cell adhesion and migration in other contexts, is highly expressed in DA-forming cells throughout DA morphogenesis and is strongly reduced in
twin peaks
.
We are testing whether
paxillin
is required for DA morphogenesis by follicle cell RNAi and by creating mutant alleles through P-element excision, perhaps
linking
tramtrack
to the cytoskeletal regulators required for cell shape change and migration. RNAi against
mirror
, which encodes a transcription factor
required for dorsal follicle cell patterning earlier in oogenesis, results in DA defects resembling
twin peaks
;
mirror
expresses in DA-forming cells during
tubulogenesis but is absent at this time in
twin peaks
. The role of
mirror
may therefore extend past epithelial patterning into morphogenesis, and
tramtrack
may be required to maintain this expression. Identification and characterization of TTK69 targets, such as
paxillin
and
mirror
, will enhance our
understanding of how regulatory factors and mechanical effectors interact to facilitate epithelial tubulogenesis.
572B
Characterization of
Pkn
dlnΔ5
, a derivative allele of the
delorean
mutation associated with the
Protein kinase N
gene in
Drosophila melanogaster
.
Georgette Sass, Allison Burke, Sarah VanOeveren, Bruce Ostrow. Grand Valley State University, Allendale, MI.
The
delorean
mutation in
Drosophila melanogaster
was identified from a collection of mutants generated in a large-scale screen of
P[IacW]
transposon
insertions on the second chromosome (Torok et al 1993 Genetics 135: 71-80). Wings of flies that are homozygous for the
delorean
mutation are held away
from the body, noticeably curved downward and have additional defects of the wing margin. The
P[IacW]
insertion has been mapped to the first intron of
the Drosophila
Protein kinase N
gene (
Pkn
) and the
delorean
mutation is thought to alter
Pkn
function (Ostrow and Momin 2001 A. Dros. Res. Conf. 42:
701B). The
delorean
wing phenotype is only seen when the
P[IacW]
insertion is homozygous (i.e
Pkn
dln
/Pkn
dln
), yet is not due to a loss-of-function mutation
as evidenced by the wild-type phenotype observed when
Pkn
dln
is heterozygous with a deficiency (
Df(2R)45C
) that removes the
Pkn
gene. This is in contrast
to other
Pkn
alleles such as
Pkn
06736
; a null allele that results in dorsal closure defects during embryogenesis (Lu and Settleman 1999 Genes Dev. 13: 1168-
1180). To understand the molecular basis of the
delorean
phenotype we have generated deletion derivatives of the
Pkn
dln
allele. One of these derivatives,
Pkn
dlnΔ5
, generates a less severe wing phenotype, but was found to have a profound effect on female fertility. In addition,
Pkn
dlnΔ5
demonstrates that the
delorean
phenotype is transvection-dependent. We determined that the molecular lesion associated with the
Pkn
dlnΔ5
allele was internal to the
P[lacW]
transposon, removing sequence from the
mini-white
+
gene. We present our continued analysis of the
Pkn
dlnΔ5
derivative with respect to the role of the
Pkn
gene in wing morphogenesis as well as its prospective role in oogenesis.
573C
larval translucida
regulates growth and morphogenesis of the Malpighian tubules.
Milan Szuperak
1
, Matthew Gibson
1,2
. 1) Stowers Institute for Medical
Research, Kansas City, MO; 2) Department of Anatomy and Cell biology, KUMC, Kansas City, KS.
The processes of growth and morphogenesis must be tightly co-regulated to generate organs of appropriate size, shape and functionality. The renal tubules
of
Drosophila melanogaster
provide an excellent model to understand organogenesis
in vivo
, although many aspects of their development remain poorly
understood. Recently, we identified and described
larval translucida
(
ltl
), a novel feedback regulator of BMP signaling during wing development. Strikingly,
homozygous null mutants of
ltl
exhibit a lethal bloated-larva phenotype characterized by excessive fluid retention, indicating a possible impairment of
Malpighian tubule function. Consistent with this hypothesis, here we report that
ltl
mutant larvae exhibit disorganization of the Actin cytoskeleton in the
tubules as well as enlarged ureters at the junction of the Malphigian tubules with the gut. These enlarged ureters appear to be blocked by gut contents, and
consistent with this, water transport from the renal tubules into the guts is strongly reduced. We further show that Malphigian tubule cell numbers are
significantly elevated in both embryos and larvae, with enlarged larval cell nuclei indicating defects in tissue growth control. We are currently investigating
the function of
ltl
in embryonic renal development, with a focus on possible roles of BMP signaling in growth and morphogenesis of the Malpighian tubules.
574A
Investigating mechanisms of tubulogenesis using tandem mass spectrometry and FISH.
Sandra G. Zimmerman, Celeste A. Berg. Department of
Genome Sciences, University of Washington, Seattle, WA.