Congress Abstracts - Society for Developmental Biology

works in concert with basal cues from the surrounding tissues for the correct spatial assembly of apical junctions and subsequent
lumen formation.
Program/Abstract # 225
Developing a Staging Scheme for Monodelphis domestica embryos
Nellett, Kolleen, (Oberlin College, USA); Morrison, Jeremy (Greensburg, PA, USA); Cruz, Yolanda P. (Oberlin College Sci Ctr, USA)
The laboratory opossum, Monodelphis domestica, is the only marsupial maintained in laboratory colonies for biological studies that
range from behavioral to genetic. The 2007 sequencing of its genome has enhanced the usefulness of this mammal in investigating
the molecular basis of many developmental events routinely precluded by the extensive embryo-maternal tissue contact that occurs
during implantation in eutherian mammals. Such events, especially organogenesis-related, occur at an exceedingly rapid pace during
the last third of pregnancy—so much so that between days 10 and 11, for example, a litter of 14 opossum embryos could consist of
individuals with somite numbers ranging from as few as 6 to as many as 28. We thus sought to devise a staging scheme based on the
appearance of landmark anatomical structures (somites, optic and olfactory vesicles, etc.), rather than pregnancy days elapsed, to make
meaningful comparisons with other vertebrate systems possible. Our results reveal the extent to which organogenetic events appear to
be disordered, relative to those in mouse, chick or human embryo (for example, development of forelimbs, oral structures, and brain
ventricles is precocious). These results will be useful for comparative studies involving organogenesis in these amniotes.
Program/Abstract # 226
PIAS-like protein Zimp7 participates in the Nodal signaling pathway during dorsal mesoderm development in zebrafish
Moreno, Roberto; Schnabel, Denhí; Salas, Enrique; Lomelí, Hilda (National Autonomous University of Mexico, Mexico)
Human ZIMP7 protein and its homolog ZIMP10 were initially identified as androgen receptor co-activators. Analysis of their
sequence revealed the presence of an SP-RING/Miz domain, which is highly conserved in members of the PIAS family and confers
SUMO-conjugating activity. The human ZIMP proteins also interact with transcription factors such as p53 or Smad3/Smad4 and with
BRG1, the catalytic subunit of the SWI-SNF remodeling complex. Accordingly, the drosophila orthologue of the Zimp genes tonalli,
was shown to interact with subunits of the Brahma complex. Mutations in tonalli produce flies with homeotic phenotypes. In zebrafish
zimp7 is ubiquitously expressed in embryos from one-cell up to 24 hpf. In this study we set out to analyze the role of zygotic Zimp7
in the early stages of zebrafish development. We found evidence indicating that Zimp7 is required for dorsal mesoderm development.
At 24 hpf, morpholino-mediated reduction of zygotic Zimp7 produced axial mesoderm defects -e.g. floor plate, precordal plate and
notocord- alterations. These defects were accompanied by an up-regulation of nodal-related genes at gastrulation such as squint, no
tail and floating head. Consistently, embryos over-expressing zimp7 RNA exhibited axial defects resembling those ones observed in
squint mutants, like forebrain loss and cyclopia and down-regulation of nodal-related genes. Altogether our results indicate that Zimp7
might be interacting with the nodal-signaling pathway during mesoderm induction.
Program/Abstract # 227
Notochord vacuoles are lysosome-related organelles that function in embryonic axis elongation and spine morphogenesis
Ellis, Kathryn Leigh; Bagwell, Jennifer; Bagnat, Michel (Duke University, USA)
The notochord plays critical structural and signaling roles during vertebrate development. At the center of the vertebrate notochord is a
large fluid-filled organelle, the notochord vacuole. While these highly conserved intracellular structures have been described for
decades, little is known about the molecular mechanisms involved in their biogenesis and maintenance. Here we show that zebrafish
notochord vacuoles are specialized post-Golgi structures and a new type of lysosome-related organelle. Through the use of dominant
negatives, mutants, and pharmacological inhibitors we show that vacuole formation and maintenance requires late endosomal
trafficking regulated by the vacuole-specific Rab32a and H + -ATPase-dependent acidification. We establish that notochord vacuoles
are required for body axis elongation during embryonic development and identify a novel role for notochord vacuoles in spine
morphogenesis. Thus, the vertebrate notochord plays important structural roles beyond early development. We are currently using live
imaging to further understand how the notochord acts as a hydrostatic scaffold during vertebrae formation. These experiments will
provide insights into the cellular mechanisms behind congenital scoliosis.
Program/Abstract # 228
Cdx and Hox genes, and body axis extension of the mouse embryo
Neijts, Roel; Monteiro, Ana-Rita; van Rooijen, Carina; Deschamps, Jacqueline (Hubrecht Institute and UMC Utrecht, Netherlands)
Mouse Cdx and Hox genes are involved in regulating the posterior elongation of axial tissues that they will subsequently pattern. They
work by maintaining active growth signaling in the embryonic growth zone. Cdx mutations cause axial truncation of varying severity
depending on the identity and number of invalidated alleles. The Hox genes also participate in axial growth, in a way obeying spatiotemporal
colinearity. While central Hox genes can replace Cdx genes in their axial growth promoting function, expression of
posteriormost Hox genes must obligatorily remain silent until later embryonic stages. We will present data documenting the
differential functional capacity of 3’ to 5’ Hox genes in modulating axial growth, exposing the relationship between Cdx and Hox
genes.
Program/Abstract # 229
Withdrawn
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