Abstracts - Society for Developmental Biology

112
Program/Abstract # 338
Vacuolar Type (H)-ATPase in zebrafish left-right asymmetric development
Gokey, Jason; Amack, Jeffrey, SUNY Upstate Medical University, Syracuse, United States
Left-right (LR) asymmetry is an interesting and complex aspect of the vertebrate body plan. The Vacuolar Type ATPase,
or V-ATPase, is a multi-subunit proton pump that maintains organelle and cellular pH by pumping protons into the
organelle lumen and out of the cellular cytoplasm. Small molecule screens have implicated the V-ATPase in vertebrate LR
development, however the underlying mechanisms remain unclear. We are using zebrafish to characterize the role(s) of the
V-ATPase during LR development. To interfere with V-ATPase function, we treated zebrafish embryos with a small
molecule inhibitor of the V-ATPase, concanamycin, or antisense morpholinos that reduce expression of aspecific V-
ATPase subunit or an accessory protein. Each of these treatments caused LR patterning defects, such as heart looping
defects, and disrupted formation of Kupffer’s vesicle (KV). Motile cilia that project into the lumenof KV generate an
asymmetric fluid flow that is required for normal LR development. Interfering with V-ATPase activity significantly
decreased the length and number of these cilia and reduced the size of the KV lumen. KVdefects in morpholino-depleted
embryos were corrected by ectopic expression of V-ATPase components. Interestingly, over-expression of a V-ATPase
accessory protein also disrupted KV, suggesting tight control of V-ATPase activity is critical for normal KV formation.
These results indicate V-ATPase function regulates KV formation, a critical step in LR development. Next, we will
elucidate mechanisms by which the V-ATPase regulates KV development and embryo LR asymmetry by examining
potential connections between V-ATPase activity and the Notch, FGF and Wnt signaling pathways.
Program/Abstract # 339
The role of the adherens junction protein aN-catenin in cranial ganglia formation
Hooper, Rachel; Taneyhill, Lisa, University of Maryland, College Park, United States
Neural crest cells are atransient, multipotent cell population that arises during neurulation and are crucial to normal
vertebrate development. After undergoing anepithelial-to-mesenchymal transition (EMT), these cells migrate to their final
destinations in the developing embryo and differentiate into a variety ofstructures throughout the adult body. Importantly,
improper neural crest cell development has been implicated in human congenital and hereditary malformations, diseases
and cancers, thus making the study of neural crest cells absolutely vital. We have previously shown that αN-catenin, a
neuralsubtype of an adherens junction protein that is expressed later in many non-neural crest neuronal derivatives, plays
an important role in controllingneural crest cell EMT and migration. Although down-regulation of αN-catenin is critical for
initial stages of neural crest cell migration, the potential functional role of αN-catenin in later neural crest cell migration
and differentiation is not known. To address this question, we investigated the spatio-temporal distribution of αN-catenin at
later stages of chick development and examined effects on neural crest cell movement and contribution to cranial ganglia
after αN-catenin perturbation.Our data reveal that αN-catenin is re-expressed by migratory cranial neural crest cells
contributing to the trigeminal ganglia. Over expression or knockdown of αN-catenin reduces or expands the migratory
neural crest cell domain, respectively, leading to a disruption in trigeminal ganglia formation that may be partially due to
effects on placode cells. Collectively, our results revealan important later function for αN-catenin in cranial neural crest
cell migration and differentiation.
Program/Abstract # 340
FOXA2 regulates cell behaviors to induce median hinge point in the neural plate
Amarnath, Smita; Bayly, Roy; Eom, Dae Seok; Agarwala, Seema, University of Texas at Austin, United States
During neural tube closure, dynamic cell behaviors at specialized regions (hinge points/HP) of the neural plate help fold it
into a neural tube. The molecular mechanisms regulating HP formation are poorly understood. We have demonstrated that
spatial and cell-cycle dependent temporal modulation of BMP signaling regulates median HP (MHP) formation by
interacting with the apicobasal polarity pathway. These interactions stabilize epithelial organization, and thuscyclic BMP
attenuation alters neuronal apicobasal polarity sufficiently to give the neural plate the flexibility to roll up and close into a
neural tube. However, the question of how the BMP signal itself is dynamically modulated remains unanswered. In this
study, we have used in vivo gene misexpression, high-resolution imaging and biochemical analyses to identify the winged
helix transcription factor FOXA2 as a potential modulator of both BMP signaling and the apicobasal polarity pathway. In
addition, we demonstrate that FOXA2 biochemically interacts with another subfamily (TGFß/Nodal) of Transforming
Growth Factor ß ligands, known to regulate cell polarity during epithelial to mesenchymal transformation. Interestingly,
increased TGFß signaling in the midbrain mimics the effects of canonical BMP blockade and FOXA2 misexpression, and
is sufficient to induce MHP formation. We propose that FOXA2 regulates apicobasal cell polarity and MHP formation by
dynamically regulating cross-talk between BMP and TGF-β/Nodal signals cascades.