Congress Abstracts - Society for Developmental Biology

Program/Abstract # 521
Mechanisms of primordial germ cell migration in the sea urchin, Lytechinus variegatus
Megan Martik, David McClay (Duke, USA)
The sea urchin small micromeres arise at the vegetal pole from an unequal 5 th cleavage, and their progeny are specified to become the
primordial germ cells of the embryo. We show, by high-resolution time-lapse microscopy, that the small micromeres reach the
coelomic pouches via a directed homing mechanism. Throughout gastrulation, small micromeres adhere to one another by LvGcadherin-mediated
adherens junctions. Once gastrulation nears completion, the tip of the gut undergoes basement membrane
remodeling that allows the small micromeres to undergo an epithelial-mesenchymal transition (EMT), and migrate over the
archenteron and to the posterior half of the forming coelomic pouch. Small micromere progeny that will become the primordial germ
cells preferentially migrate to the left coelomic pouch while a smaller number reach the right coelomic pouch and are apoptosed with
the larval support system during metamorphosis. Ectopically placed small micromeres also home to the coelomic pouches. When
placed at the equator of the 16-cell embryo, the small micromeres undergo a precocious EMT at the mesenchyme blastula stage and
actively migrate to the tip of the early archenteron during its invagination. Ectopic insertion of 32-cell-stage small micromeres into the
blastocoel of an early gastrula host embryo is followed by attachment of the small micromeres to the archenteron tip as soon as they
become motile, independent of LvG-cadherin adherens. Current aims are to understand the signaling and chemoattractant mechanisms
by which the small micromeres undergo such a dramatic feat of finding their way home.
Program/Abstract # 522
Identifying the link between Nodal signaling and cell migration within the cardiac cone
Rowland, Jessica R. (Princeton, USA)
Asymmetries in the zebrafish heart are established through a series of dynamic cell migrations. The first migration event, known as
cardiac jogging, consists of the conversion of the cardiac cone into the linear heart tube. Recent work from our lab has shown that the
laterality of cardiac jog is directed by Nodal expression through increasing cell migration rates of the left atrial cells. My work focuses
on gaining a better understanding of how Nodal signaling influences cardiac cell movements during the establishment of asymmetries.
We recently conducted a microarray designed to identify novel downstream genetic targets of Nodal signaling within the heart. Our
results suggest that Nodal may influence several cell biological events including additional TGFbeta signaling pathways, interactions
with the extracellular matrix, and regulation of the actin cystoskeleton. Our preliminary results suggest that Nodal-mediated changes
in cell migratory behavior are due to changes in small GTPase activity. Our transcriptional analysis identifies a set of small GTPases
that may regulate actin dynamics and endocytosis during this event. We will present our efforts to characterize the function of these
small GTPases and our attempts to correlate changes in actin dynamics during jogging.
Program/Abstract # 523
LifeMap Discovery: The embryonic development, stem cells, and regenerative medicine research compendium
Edgar, Ron; Mazor, Yaron; Rinon, Ariel; Blumenthal, Jacob; Golan, Yaron; Buzhor, Ella; Livnat, Idit; Ben-Ari, Shani; Lieder, Iris;
Shitrit, Alina; Gilboa, Yaron; Edri, Osnat; Shraga, Netta; Bogoch, Yoel; Leshansky, Lucy; Aharoni, Shlomi (LifeMap Sciences,
Israel); D. West, Michael (BioTime Inc., USA); Warshawsky, David; Shtrichman, Ronit (LifeMap Sciences, Israel)
In-depth understanding of the differentiation processes occurring during embryonic development is instrumental toward derivation of
functional stem cells in vitro. Profiling the genes and signals regulating mammalian cell differentiation is essential for identification
and classification of stem cells, and to foster design of differentiation protocols and therapeutic products. LifeMap Discovery TM ,
http://discovery.lifemapsc.com, maps the ontology of cellular development and stem cell differentiation. The database is based on
systematic assimilation of scientific data detailing distinct developmental paths, from the progenitor cells until determination of their
terminal fates. The database encompasses cellular and anatomical development, supplemented with qualitative gene expression
patterns, signaling pathways, in-situ hybridization and high throughout experimental data, related diseases, images and relevant
references.
The database is divided into the following: 1. In-vivo development - cell lineages arising in the embryo. 2. Stem cell differentiation -
cultured cells and differentiation protocols. 3. Gene expression and signaling – gene expression and signaling cascades related to
development and differentiation. 4. Regenerative medicine – application of stem cells in therapeutics. These four segments are
connected and interlaced by computational and hand-curated methods. Most noteworthy, are the in-vivo entities which are linked to
their closest in-vitro entities, based on gene expression analysis. LifeMap Discovery's value lies in the combined power of the
presented data, which enables identification and prediction of differentiation paths and potential regenerative medicine applications.
Program/Abstract # 524
Induction of osteo-chondroprogenitors formation by transcription-factor mediated reprogramming process
Cheung, Martin; Wang, Yinxiang; Lu, Lorraine; Wu, Ming-Hoi; Sham, Mai-Har; Chan, Danny; Cheah, Kathryn (The University of
Hong Kong, China)
Stem-cell based skeletal tissue engineering has been limited by its heterogenous and uncontrolled differentiation. Osteochondroprogenitors
co-expressing Sox9 and Runx2 are lineage restricted skeletal precurors to differentiate into chondrocytes and
osteoblasts without generating other cell types favourable for skeletal regeneration. Therefore, developing tactics to generate osteochondroprogenitors
are essential.
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