Congress Abstracts - Society for Developmental Biology

Program/Abstract # 360
Differential Expression of Extracellular Matrix Proteins During Posterior Commissure Development
Stanic, Karen; Gonzalez, Melissa; Montecinos, Hernán; Caprile, Teresa (Universidad de Concepcion, Chile)
The function of the mature nervous system depends upon the right formation of highly complex neuronal circuits. Accordingly, a
critical phase of early nervous system development is the establishment of appropriate connections between neurons and their target
cells. The formation of these precise “wiring” patterns is controlled by the ability of the leading edge of an axon, termed the growth
cone, to sense a combination of environmental cues and make choices based on the extracellular information consisting on soluble,
membrane-bound and extracellular matrix molecules. The posterior commissure is an axonal tract located in the roof plate of the
pretectal region between the most caudal prosomere (prosomere 1) and the mesencephalon. Previous result from our laboratory
identify SCO-spondin as a major contributor on axonal behavior among prosomere 1 commissural roof plate, never the less how these
axons arises from the pretectal nucleus present in the ventral region towards the dorsal zone is still to be elucidated. In this work we
provide immunohistochemical evidence about differential expression of extracellular matrix protein (EMP) in the alar plate and floor
plate of the commissural region of the prosomere 1 during PC development. We have identified so far 8 different EMP in this region:
Chondroitin sulphate, Decorin, Fibronectin, HKN-1, Laminin, Perlecan, Osteopontin and Tenascine, all of them with specific trails of
expression, i.e. tenascine and HKN-1 posses the same expression pattern in the alar plate opposite to SCO-spondin, however laminin
present a highly similar pattern of this latter. Taken all together this work generates a topographic expression map where commissural
axons are able to navigate in order to form the PC. Grant Sponsor: FONDECYT 1110723.
Program/Abstract # 361
The Ubiquitin ligase activator APC/C-Cdh1 (Rap/Fzr) regulates retinal axon targeting in the developing Drosophila eye
Venkatesh, Tadmiri; Gronska, Marta (City College of New York, USA)
The precise targeting of axons and formation of specific connections during development is critical to nervous system functioning and
the mechanisms that regulate axon targeting are not fully understood. During development of the Drosophila compound eye
photoreceptor (R cell) axons target stereotypically to specific layers of the optic ganglia (medulla and the lamina). To test for the
involvement of ubiquitin ligases in axon targeting, we have examined the role of Drosophila–Cdh1 (Rap/Fzr) in retinal axon growth
and targeting in the developing eye. Drosophila-Cdh1 (Rap/Fzr) is the activating subunit of the conserved ubiquitin ligase, anaphase
promoting complex/ cyclosome (APC/C). In loss-of-function Drosophila–Cdh1 mutants retinal axons fail to terminate properly
leading to aberrant axonal patterning in the optic ganglia. Experiments using ro-tau-lacZ constructs show that, in loss of function
Cdh1 (Rap/Fzr) mutants photoreceptor R2-R5 axons fail to stop in the lamina and miss-target to the medulla layers. Conversely, gainof-function
of Cdh1 (Rap/Fzr) leads to premature termination and clumping of R cell axons. In addition, genetic mosaic analyses
experiments using FLP-FRT and GAL4-UAS techniques show that Cdh1 (Rap/Fzr) functions in a cell autonomous manner. Our
studies suggest that Cdh1 (Rap/Fzr) functions as a regulator of axon targeting during Drosophila visual system development. These
results are consistent with other mammalian studies reporting a role of Cdh1 in axon growth and targeting and provides further
insights into the conserved neuronal functions of the ubiquitin ligase complex APC/C Cdh1 .
Program/Abstract # 362
Withdrawn
Program/Abstract # 363
Cell-lineage analysis and localization of the embryonic sinoatrial node precursor cells during early mouse development
Molero Abraham, Mª MAgdalena; Franco, Diego; Aránega Jiménez, Amelia; Dominguez Macias, Jorge Nicolas (Universidad de
Jaén, Spain)
The early heart forms from two mesodermal cell populations, called the First and Second Heart Fields (F&SHF). C ell lineage tracing
experiments using the SHF marker islet1, have revealed that the left ventricle derives exclusively from FHF, whereas the outflow
tract, right ventricle and the atria are of mixed F&SHF origin (Cai et al, 2003). More recently it has been demonstrated that sinoatrial
(SAN) and atrioventricular (AVN) nodes are partially SHF-derived (Moretti et al, 2006; Sun et al, 2007). However the contribution of
SHF-islet1 cells to the distinct components of the ventricular conduction system, as well as, the localization of SAN and AVN islet1-
precursor cells, are still unknown. Using dye-injections within the posterior portion of the SHF (pSHF), we previously demonstrated
that atria and atrioventricular canal are pSHF-derived (Domínguez et al, 2012). Now, we are interesting to determine whether SAN
and AVN islet1+ precursor cells are placed at the pSHF and, moreover, whether islet1+ progenitor cells contribute as well to His-
Purkinje system development. Preliminary results from dye-injections experiments reveal that, in most cases, right and left pSHFderived
cells populate ipsilaterally the embryonic atria. However, some dye-labelled cells were placed at the right atria-sinus venous
junction, where the pacemaker marker, HCN4, is expressed and define the putative SAN precursor. These results would suggest that
islet1+ progenitors cells within the pSHF participate in the developing of both, the working and conduction system myocardium, and
open new ways to explore the putative SHF origin of the distinct CCS elements.
Program/Abstract # 364
Dissecting the roles of the proepicardium, Fgf10 and Fgf3 in cardiac development
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