Abstracts - Society for Developmental Biology

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Elevated nuclear translocation of NF-κB was also discovered in lungs from transgenic mice. An evaluation of genes
regulated by NF-κB demonstrated elevated expression of Fas ligand, suggesting increased activity of the Fas-mediated
signaling pathway in which ligand-receptor interaction triggers cell death. These data provide evidence that RAGE
expression must be tightly regulated during organogenesis and that RAGE signaling during branching morphogenesis may
provide insight into the progression of developmental lung anomalies including bronchopulmonary dysplasia.
Program/Abstract # 137
Glycosaminoglycan biosynthesis is required non-cell-autonomously for correct patterning of the dorso-anterior
Drosophila eggshell by the Epidermal Growth Factor Receptor ligand Gurken
LeMosy, Ellen K.; Neiswender, Hannah, Georgia Health Sciences University, Augusta, United States
Graded EGF-R signaling within the follicle cell epithelium occurs in response to a germline-derived ligand, Gurken (Grk),
secreted dorso-anteriorly near the position of the oocyte nucleus. High Grk levels specify dorsal midline, intermediate
levels specify position of the dorsal appendages, and lowest levels allow expression of Pipe ventrally to later define the
dorsoventral axis of the embryo. Prior studies by Li-Mei Pai’s lab showed that over-expression of Dally-like, a membranelinked
heparan sulfate proteoglycan (HSPG), results in a shallower extracellular gradient ofGrk and a reduced gap between
the dorsal appendages, indicating loss of high-Grk domain, while the Pai lab and David Stein’s lab report that Fringe
Connection (frc) and Sulfateless (sfl), enzymes involved in HS synthesis and sulfation, respectively, are not required for
eggshell patterning. We examined strong mutant alleles of protein O-xylosyl transferase (oxt), the first and rate-limiting
enzyme acting in glycosaminoglycan (GAG) synthesis. Egg chambers containing anterior or complete oxt-mutant follicle
cell clones show increases in size of the dorsal gap between dorsal appendage primordia from 3-4 cells wide to up to 6-7
cells wide, while small clones do not exhibit cell-autonomous changes in fate. These findings suggest loss of follicle cellderived
GAGs is associated with expansion of the high-Grk domain. The most notable change in Grk distribution is its
ectopic presence within germline vesicles in affected egg chambers. One possibility suggested by this data is that there is
reduced uptake and degradation of Grk by follicle cells when it is not bound to GAGs, leading to increased EGF-R
signaling and perhaps alternative uptake into the oocyte.
Program/Abstract # 138
Mirror and Paxillin act downstream of Tramtrack69 to regulate tube morphogenesis in the Drosophila ovary
Peters, Nathaniel C., University of Washington Genome Sciences, United States
Epithelial tubes are essential for organ and tissue function, and faithful tubulogenesis requires precise orchestration of cell
signaling, shape change, migration, and adhesion. Epithelial follicle cells in the Drosophila ovary undergo morphogenesis
to form a pair of tubes, the apical lumens of which act as molds for the egg shell respiratory filaments, or dorsal
appendages (DAs); this system is a robust and accessible model for studying epithelial tube patterning, formation, and
expansion. The Tramtrack69 (TTK69) transcription factor controls DA lumen volume by regulating apical surface area
and tube expansion; the twin peaks mutant reduces TTK69 levels specifically late in oogenesis, inhibiting tube expansion
and stunting the DAs. Microarray analysis of wild type and twin peaks ovaries, followed by in situ validation of candidates,
identified mirror and paxillin as TTK69 targets. mirror encodes a homeodomain protein that patterns the epithelium prior
to DA tubulogenesis, but post-patterning RNAi-knockdown disrupted DA tube expansion, indicating that mirror may have
a novel role in DA tubulogenesis. paxillin expression is highest in the DA tube cells just prior to tube expansion, and
RNAi-knockdown of paxillin resulted in DA tube defects. We are now determining whether Paxillin, a scaffolding protein,
interacts with Integrin-based cell adhesions, JNK signaling, and/or GPCR signaling, all of which are required for DA
tubulogenesis, and whether TTK69 regulates paxillin via a mirror-dependent pathway. Further characterization of TTK69
targets, such as paxillin and mirror, will help illuminate the network of transcription factors, signaling pathways, and
cytoskeletal regulators required for epithelial tube morphogenesis.
Program/Abstract # 139
ErbB signaling within Schwann cells controls quiescence of zebrafish lateral line progenitor cells through
regulation of Wnt and FGF signaling.
Lush, Mark E., Stowers Institute for Medical Research Research, United States; Piotrowski, Tatjana (Stowers Institute for
Medical Research, Kansas City, MO, United States)
The Zebrafish lateral line is a mechanosensory system consisting of neuromasts containing support cells and sensory hair
cells. The formation of the lateral line has proven an excellent model for the study of developmental events, such as
collective cell migration. Here we show that it is also a unique model to study stem cell biology. Previous work from our
laboratory revealed a role for glia in negatively regulating proliferation and differentiation of lateral line stem cells.
Mutations in erbb2, erbb3b and nrg1-3 have increased neuromast numbers. We show by transplantation experiments and