Congress Abstracts - Society for Developmental Biology

neural tube morphogenesis, is conserved as PCP signaling is required for this process in all vertebrates analyzed thus far. During NCE,
neuroepithelial cells elongate and extend medially-oriented protrusions to migrate towards the midline, however the mechanisms that
direct this process are poorly understood. Our laboratory has identified the receptor neogenin (neo) and its ligand the repulsive
guidance molecule rgma as candidates that regulate cell movement during NCE. In the absence of neo, cells extend randomly oriented
protrusions that impede migration towards the midline. neo-depleted embryos also exhibit an aberrant microtubule network (MTs),
implicating MTs in regulating the directionality of membrane protrusions during NCE. Studies using Xenopus suggest that polarized
migration is regulated by a secreted signal emanating from the notochord that promotes migration towards the midline. Interestingly,
rgma is strongly expressed in the notochord and may be cleaved from the plasma membrane raising the possibility that it functions as
the postulated midline-derived signal that provides directional cues during NCE. To test this hypothesis, a transgenic line
misexpressing rgma away from the notochord and exhibit delayed NCE has been generated. Current efforts aim to analyze the cell
behaviors of mRFP labeled cells using time-lapse microscopy to determine if ectopic rgma expression influences the polarization of
cell movement in the neural tissue during NCE.
Program/Abstract # 511
Candidate Modulators of Tubulin and Microtubule Dynamics in C. elegans Neural Development
Baran, Renee; Kim, Hyun Su; Shayler, Dominic (Occidental College, USA)
tba-1 encodes an alpha-tubulin widely expressed during C. elegans development. We showed previously that a dominant allele, tba-
1(ju89), causes defects in motor neuron development and uncoordinated movement. To identify TBA-1-interacting proteins and study
how microtubule dynamics and function are regulated in developing neurons, suppressors of tba-1(ju89) were isolated in a genetic
screen based on reversion to wildtype movement and synaptobrevin-GFP expression. SNP analysis was used to map two suppressors
to separate regions of C. elegans chromosome III, and whole genome sequencing identified mutations in the klp-7 and zer-1 genes.
klp-7 encodes a member of the kinesin-13/MCAK family which activate microtubule depolymerization. Experiments are in progress
to test if -KLP-7 expression and activity is altered in tba-1(ju89) mutants. Alternatively, altered KLP-7 activity in the suppressor
mutant may compensate for another defect in microtubule dynamics. zer-1 encodes a conserved substrate recognition subunit of an
ubiquitin-mediated protein degradation complex. ZER-1 contains a VHL Box motif and interacts with C. elegans cullin-2 (Vasudevan,
et al. 2007), but its substratres are unknown and it has not been implicated previously in neural development. ZER-1 may play a role
in regulating tubulin stability directly or modulate expression of other regulators of microtubule dynamics.
Program/Abstract # 512
Live imaging of trunk neural crest cells in zebrafish reveals a role for Notch signalling
Richardson, Joanna; Linker, Claudia (King's College London, UK)
The vertebrate neural crest (NC) is a transient migratory cell population that forms early in development, at the border of the neural
plate. After induction, NC cells migrate extensively and differentiate into a wide range of cell types (melanocytes, glia, neurons, etc.).
NC migration shares numerous characteristics with metastasis: both involve the loss of epithelial polarity, changes in expression of
adhesion molecules and activation of matrix metalloproteinases; and NC cells themselves are often the tissue of origin for several
types of cancer, e.g. melanoma and neurofibromatosis. The Notch signalling pathway has been implicated in cell migration and
cancer, and Notch has been shown to play a role in NC induction. Our work demonstrates a role for Notch signalling in trunk NC
migration in zebrafish. Trunk NC cells express receptors and downstream targets of the Notch pathway, whereas adjacent cells express
its ligands. Gain and loss of Notch function delays NC migration. Combining the use of a new transgenic line in which we can track
NC nuclei and membranes in vivo with a new tracking algorithm for 3D movement we have been able to quantify the behaviour of
NC cells. This analysis indicates that Notch is important to regulate the persistence and directionality of NC migration. In other
developmental contexts, Notch has been shown to distinguish between leader and follower cells in collective cell migration. We are
investigating the collective migratory behaviour of the NC population and the possible role of Notch signalling in this process.
Program/Abstract # 513
Poster Board # B81
Histone Deacetylase 9b is involved in neural crest development.
Espina, Jaime A.; Barriga, Elías H.; Reyes, Ariel E. (Univ Andrés Bello, Chile)
Histone deacetylases (HDACs) are proteins that remove acetyl groups from histones, leaving the chromatin on a compact state, which
is usually associated with gene repression. HDACs also can interact with transcriptions factors in the nucleus to regulate gene
expression. The function of several HDACs has been recently described during development of different organism. In our laboratory
we are interested in the function of HDAC9b, in the development of zebrafish neural crest. By using morpholinos against Hdac9b we
generate the knockdown of this protein. Our results show that the cranial cartilage (derived from neural crest) is not properly formed
in morphant embryos. Using in situ hybridization against neural crest induction (foxd3, tfap2) and migration (crestin) markers, we
determined that the neural crest induction is not affected but the migration of these cells was severely impaired. Using transgenic line
Tg(sox10:eGFP) we have confirmed in vivo effect on cell migration on knockdown embryos. Our data suggest strongly a role of
Hdac9b on neural crest cells migration, but not on NCC induction, and that Hdac9b is essential for the proper formation of cranial
cartilage.
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