Congress Abstracts - Society for Developmental Biology

signalling during gut and enteric nervous system (ENS) development. Methods: Talpid 3 embryos were fixed at different time points,
and processed for immunohistochemistry to identify cell types and morphology, and in situ hybridization for genetic pathway
analyses. To assess the cell autonomous requirement of the cilia in ENS development, we used intra-species grafting between Talpid 3
and GFP chickens. Results: Talpid 3-/- gut showed significantly reduced length, tracheoesophageal fistula and open hindgut. Although
enteric neural crest cell (ENCC) derivatives were distributed along the gut, ENCC were scattered throughout the gut wall, rather than
arranged in typical plexuses. Transplantation of wild type ENCC to Talpid 3 mutants did not rescue this phenotype. Defects in the
patterning of the Hh pathway components in the Talpid 3 mutants correlated with the defects in smooth muscle. Conclusions: We
describe a number of phenotypic defects in Talpid 3 mutant gut suggesting it is a useful model to study the genetic basis underlying
related human gut abnormalities. We demonstrate that cilia-mediated Hh signalling is not necessary for ENCC migration, but is
essential for normal smooth muscle formation and ENS patterning.
Program/Abstract # 330
The dynamic right-to-left translocation of Cerl2 is involved in the regulation and termination of Nodal activity in the mouse
node
Belo, José A.; Inácio, José M.; Marques, Sara (Universidade do Algarve, Portugal); Nakamura, Tetsuya; Shinohara, Kyosuke (Osaka
University, Japan); Meno, Chikara (Kyushu University, Japan); Hamada, Hiroshi (Osaka University, Japan)
The determination of left-right body asymmetry in mouse embryos depends on the interplay of molecules in a highly sensitive
structure, the node. Here, we show that the localization of Cerl2 protein does not correlate to its mRNA expression pattern, from 3-
somite stage onwards. Instead, Cerl2 protein displays a nodal flow-dependent dynamic behavior that controls the activity of Nodal in
the node, and the transmission of the laterality information to the left lateral plate mesoderm (LPM). Our results indicate that Cerl2
initially localizes and prevents the activation of Nodal genetic circuitry on the right side of the embryo, and later its right-to-left
translocation shutdowns Nodal activity in the node. The consequent prolonged Nodal activity in the node by the absence of Cerl2
affects local Nodal expression and prolongs its expression in the LPM. Simultaneous genetic removal of both Nodal node inhibitors,
Cerl2 and Lefty1, sustains even longer and bilateral this LPM expression.
Program/Abstract # 331
Cilia, Flow Sensing, and Polycystins: How the Embryo Determines Left From Right
Grimes, Daniel T. (Princeton University, USA), Keynton, Jennifer; Beunavista, Maria (MRC Harwell, UK); Hamada, Hiroshi;
Shinohara, Kyosuke (Osaka University, Japan); Norris, Dominic (MRC Harwell, UK)
The left-right asymmetry of the internal organs of vertebrates is determined during development by a biophysical mechanism;
asymmetric fluid flow. In the mouse embryo, a leftward flow is generated in the node by polarized cilia that rotate around 10 times per
second. Flow induces asymmetries in gene expression in crown cells around the periphery of the node. These subtle asymmetries are
then transmitted to the lateral plate mesoderm where the Nodal signaling cascade is established in the left side of the embryo only.
However, the connection between leftward flow and asymmetric gene expression has not been mechanistically established. Our work
on the sensory polycystin proteins PKD1L1 and PKD2 has revealed a novel pathway linking the generation and sensation of flow to
the initiation of gene asymmetries around the node. Rather than being required to initiate left-sided Nodal signals, the flow sensor
PKD1L1 is instead needed to restrict Nodal to the left side. It has been a matter of continued debate whether symmetry is broken by
direct mechanosensation of the force of flow or by the perception of an asymmetrically positioned chemical within the node. We find
that a small extracellular domain of PKD1L1 is essential for function; a mutation within this domain alters its structure and causes
severe left-right defects in the mouse. Together, our findings favor a model in which flow is mechanically sensed in a PKD1L1-
dependent manner to derepress left-sided Nodal signaling.
Program/Abstract # 332
Sp5l is a novel transcription factor involved in the establishment of left-right asymmetry in early zebrafish development
Inglis, Rachael (University of Cambridge,UK); Nelson, Andrew; Soong, Daniel (King's College London, UK); Amack, Jeffrey (SUNY
Upstate Medical University, USA); Wardle, Fiona (King's College London, UK
The zebrafish gene sp5l (sp5-like) encodes a zinc finger transcription factor of the SP1 family. It is expressed in both ectodermal and
mesodermal tissues during early development, including the dorsal forerunner cells (DFCs) which subsequently develop into
Kupffer’s vesicle: the ciliated organ of asymmetry in zebrafish. Using a morpholino knockdown approach, we have found that sp5l is
required for the proper establishment of left-right asymmetry in the early embryo. This role is not shared with the related gene, sp5,
despite their co-expression in the DFCs. Our functional characterisation of sp5l has revealed roles in both the formation and function
of Kupffer’s vesicle, primarily in control of the anti-clockwise fluid flow generated by motile cilia within the vesicle. As sp5l encodes
a transcriptional regulator, we have attempted to identify downstream target genes that could mediate its effects on Kupffer’s vesicle
development by performing genome-wide expression analysis by microarray. We have also investigated the upstream regulation of
sp5l by various signalling pathways, with particular focus on the control of its expression in the DFCs and Kupffer’s vesicle.
Program/Abstract # 333
ATRX function during zebrafish early development
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