Abstracts - Society for Developmental Biology

24
Program/Abstract # 74
A developmental biologist’s foray into science policy
Grant, Kelly A., Gannon University Biology, Erie, United States
The American Association for the Advancement of Science (AAAS) offers science policy fellowships to scientists of all
disciplines. The fellowship promotes mutually beneficial relationships where scientists share their expertise and analytic
skills with Congressional offices and executive branch agencies while scientist learn about policy. As a developmental
biologist my policy interests focused on the effects of environmental pollutants on development, especially exposure to
endocrine disruptors. Based on these interests, I selected an office at the EPA that offered me the opportunity to evaluate
toxicological profiles of chemicals and devise plans to reduce the use of chemicals of concern. In my two years at the EPA,
I developed the strategy to reduce human and environmental exposure to bisphenol A (BPA), which included an initiative
to find safer replacements to BPA in thermal paper receipts. I also worked on programs to reduce the release of
nonylphenol to the environment. Nonylphenol (aka Triton X-100) is roughly 1000xs more estrogenic than BPA and is
recalcitrant to biodegradation. Reducing the environmental releases of these chemicals will hopefully ameliorate conditions
leading to the feminization of fish, occurring in many lakes and rivers. During my fellowship, I learned about policy
making, gained experience communicating to non-biologists, and applied knowledge of developmental biology to
environmental policies. I interfaced with toxicologist to develop more meaningful assays to better capture critical stages in
development and/or disruption of signal transduction pathways. Finally, the work was exceptionally rewarding because it
created concrete, real-world benefits. The poster will discuss my projects in more detail and I will have information about
the fellowship.
Program/Abstract #75
Dynamic filopodia transmit lont-range Shh signaling during tissue patterning.
Barna, Maria; Martin, Esther Llagostera; Sanders, Timothy, UC San Francisco, United States
The movement of key signaling proteins within tissues and organs is a central feature of metazoan development that must
be exquisitely spatially controlled. How this is achieved at a cellular level remains poorly understood. Here we constructed
a robust, state-of-the-art imaging system that allows for visualization of signaling at single cell resolution under
endogenous spatial and temporal control within living vertebrate embryos. Through this imaging approach, we identified
that genetically defined populations of mesenchymal cells involved in Sonic Hedgehog (Shh) signaling within the
vertebrate limb bud possess a novel specialized class of actin-based filopodia spanning several cell diameters that have not
been previously described. By imaging Shh responding cells in real time, we visualized an exquisite distribution and colocalization
of the Shh co-receptors to discrete micro-domains along the membrane of these filopodia extensions,
suggesting a functional role in facilitating long-range signaling. We therefore developed a tightly regulated expression
system directed by the Shh limb-specific enhancer element to visualize Shh production in vivo. Remarkably, imaging Shh
ligand itself revealed that it is normally produced in the form ofa particle that dynamically moves along filopodia
extensions and accumulates at their tips, which make stabilized contacts with responding cells that contain Shh coreceptors.
Strikingly, these stabilized interactions are associated with a dramatic accumulation of Shh to the primary cilium
of responding cells and activation of the pathway. To our knowledge, this is the first in vivo demonstration of Shh ligand
production and movement. These findings strongly suggest that contact mediated release propagated by specialized
filopodia contributes to the delivery and activation of Shh signaling at a distance. Together, these studies identify a new
mode of communication between cells that extends our understanding of long-range signaling during vertebrate tissue
patterning.
Program/Abstract # 76
Characterization of a Wls knockdown in the developing chick spinal chord
Allen, Sean, San Francisco State University, United States
The Wnt signaling pathway contributes to the regulation of important developmental and cellular events, such as cell
survival, proliferation, and specification. Within vertebrates, one of the best-characterized examples of a Wnt gradient is
found in the developing spinal cord. There, dorsally expressed Wnts form a dorsal to ventral gradient of proliferation and
neuronal specification. For Wnts to function properly, they must first be secreted from Wnt-producing cells. Wntless
(Wls), a transmembrane protein, is necessary for the secretion of all known Wnt family members invertebrates. Knockout
of Wls in the mouse model system causes early embryonic lethality that coincides with the timing of the first known
requirement for Wnt signaling. The goal of this project was to determine the role of Wls in Wnt gradient formation in the
chick spinal cord. Specifically, we hypothesized that loss of Wls would disrupt the Wnt gradient and thereby cause defects
in survival, proliferation, and patterning. To test this hypothesis, electroporation was used to achieve a transient siRNAmediated
knockdown of Wls. Transverse sections were analyzed for morphological changes, the most noticeable of which