Abstracts - Society for Developmental Biology

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and migration (ADAM13). They act both by cleaving the extracellular domain of Cadherin-11 to release an active
extracellular domain promoting cell migration and by regulating gene expression via their cytoplasmic domain. While
ADAMs are critical for CNC migration in vivo they are not essential for CNC migration in vitro. Here we analyze how the
in vivo environment restricts CNC migration in the absence of ADAM, and how the cytoplasmic domain controls gene
expression and ADAM function. Our results show that cells within the CNC explants are able to modulate their adhesion to
migrate through 20 µm “tunnels” in vitro whether they express ADAM13 or not. Their ability to invade a collagen gel is
also not affected. In contrast, mechanically opening the CNC pathways in vivo is sufficient to rescue migration in embryos
lacking ADAM13. We further show that ADAM13 function in the CNC depends on a series of phosphorylation by GSK3
and polo like kinase and that this is independent of ADAM13 proteolytic activity. We propose a unified model describing
how ADAMs metalloproteases can control cell migration during early embryogenesis and possibly in cancer cell
metastasis.
Program/Abstract # 96
Elucidating the role of Stat3 signaling in development of early cranial neural crest stem cells, cranial NC cell
derived tissue and coronal suture formation
Dasgupta, Krishnakali, Keck School of Medicine - USC, United States
Neural crest stem cells (NCSCs) are the transient population of multipotent stem cells that arising in gastrulating vertebrate
embryos at the future neural plate and non-neural ectoderm junction, that traverse to various parts of the embryo producing
mainly Ectodermal derivatives like neurons, glial cells and melanocytes, along with Mesodermal derivatives like bone,
cartilage or smooth muscle (only in cranial neural crest cells). Microarray studies performed on clonally cultured Cranial
neural crest cell lines in the lab revealed high levels of expression of members of the Jak2-Stat3 signaling cascade,
prompting us to investigate a possible role the Stat3 signaling in this lineage. Subsequently, gross morphological defects in
neural crest derived tissue was observed in mice with conditional knockout of Stat3 in neural crest specific cell lineage
(under the Wnt-1 Crepromoter) beginning early during neural crest derived tissue development, along with premature
lethality. Surprisingly these mice (Wnt1Cre;Stat3 flox/flox) also developed partial bilateral Coronal suture synostosis with
a 100% penetrance by 3 weeks, supporting recently published findings that HIES (Hyper –IgE Syndrome )/Job’s
syndrome, a rare immunological disorder with patients displaying characteristic facial deformities including
Craniosynostosis, is genetically linked to a mutation in the DNA binding domain of the Stat3 gene resulting in nonfunctional
Stat3 proteins (loss of DNA binding capacity). Currently we are trying to elucidate how the Neural crest specific
loss of the Stat3 gene leads to the loss of defined Coronal suture boundary and mixing of osteoblastic cells early during
Suture formation in Wnt1Cre; Stat3 flox/flox mice.
Program/Abstract # 97
Fat-Dachsous signaling coordinates polarity and differentiation of the craniofacial skeleton in zebrafish
Le Pabic, Pierre; Schilling, Thomas, University of California, Irvine, United States
Little is known about the mechanisms of cell-cell communication necessary to assemble skeletal elements of appropriate
size and shape. Skeletal progenitors may behave as coherent units by communicating via the planar cell polarity (PCP)
pathway. In Drosophila, two sets of factors control PCP independently: the Fat and the non-canonical Wnt signaling
systems. While a requirement for components of the non-canonical Wnt system was recently demonstrated in regulating
the oriented divisions and intercalations of chondrocytes in the growth plates of long bones, a role for the Fat system in
skeletal development has not been reported. We find that loss of Fat, Dachsous, Four-jointed or Atrophin-orthologues in
zebrafish results in similar skeletal abnormalities, including the shortening of some cartilages, fused joints and chondrocyte
stacking defects. Confocal imaging of Fat- or Dachsous-deficient prechondrocyte condensations reveals loss of stacking
and polarity – two PCP-regulated behaviors in other contexts such as gastrulation, as well as delays in differentiation. In
addition, our chimaeric analysis demonstrates that Fat is both necessary and sufficient to coordinate polarity and
differentiation of cartilage in a non-cell autonomous manner. These results provide genetic evidence that skeletal
morphogenesis and differentiation are controlled through a conserved Fat signaling pathway, a process that has not
previously been associated with defects in skeletal tissuepolarity.
Program/Abstract # 98
Response genes regulate the severity of craniofacial defects
Sheehan-Rooney, Kelly; Seritrakul, Pawat; Eberhart, Johann, Univ of Texas at Austin, United States
Craniofacial malformations are highly variable birth defects, yet we understand little about the pathways regulating this
phenotypic variability. To identify and characterize these pathways, we examined the variable craniofacial defects in
zebrafish gata3 mutants. In human, mutation of GATA3 causes the highly variable HDR syndrome (Hypoparathyroidism,