Congress Abstracts - Society for Developmental Biology

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Program/Abstract # 514 Ric-8A is required for the neural crest cell migration Toro-Tapia, Gabriela; Fuentealba, Jaime; Rodriguez, Marion; Hinrichs, Maria Victoria; Olate, Juan; Marcellini, Sylvain; Torrejon, Marcela (Univ de Concepcion, Chile) Ric-8A is a highly conserved protein with GEF (Guanosine Exchange Factor) activity for different Gα subunits related with heterotrimeric G protein signaling. Ancestral Ric-8 is critical to asymmetric cell divisions in non-vertebrate organisms and recently a similar function was reported for Ric-8A in mammalian cells. In addition, Ric-8A is expressed in neural and neural crest cells during vertebrate development. In our laboratory we have observed that Ric-8A is necessary to the proper neural crest cells migration during Xenopus tropicalis development. Our goal is to study the mechanism how Ric-8A is involved in the migration of cranial neural crest (CNC) cells. First, we evaluated the effect of loss and gain of function of Ric-8A by injecting a specific morpholino or mRNA, respectively, and then we analyzed the effect over the cell morphology during cell migration on CNC explants. We observed that the overexpression of Ric-8A did not affect the migration of the CNC cells although the silencing of Ric-8A strongly abrogated the normal migration of these cells. Immunocytochemistry showed that Ric-8A is localized mainly at the cell cortex in explants of CNC cells. In addition, loss of function of Ric-8A altered the sub-cellular localization of aPKC, a protein involved in cell polarity. On the other hand, Ric-8A down regulation decreased the number of focal adhesion to fibronectin matrix. Finally, we proposed that Ric-8A acting through heterotrimeric G proteins plays essential roles during the migration of CNC cells, possible by regulating cell polarity and/or cell adhesion properties. Program/Abstract # 515 Dynamic migratory behaviours of mouse sacral neural crest cells Chan, Wood Yee; Chen, Jie-Lin; Wang, Xia (The Chinese Univ of Hong Kong, China); Enomoto, Hideki (RIKEN Center for Developmental Biology, Japan) The neurons and glial cells of the distal hindgut are derived from two sources of the neuraxis: vagal and sacral neural crest. Vagal neural crest cells (NCCs) enter the rostral foregut at E9.5 and migrate rostro-caudally to reach the distal hindgut at E14.5, while sacral NCCs enter the caudal hindgut via pelvic ganglia at E13.5 and migrate caudo-rostrally toward the proximal hindgut. These two populations of NCCs together form a complete neuronal network in the hindgut. The aim of the present study was to examine with time-lapse live cell confocal imaging the dynamic migratory behaviours of sacral NCCs both within hindgut explants ex vivo and when they were cultured in vitro. Within the hindgut explants, sacral NCCs migrated along nerve fibres extending from the pelvic ganglia. When a sacral NCC met a vagal NCC on a nerve fibre, they collided, pushed against each other and then intermingled to form a cellular network with more vagal than sacral neural crest-derived cells. In vitro, sacral NCCs also migrated along nerve fibres from the pelvic ganglia. When the fibre extension from the pelvic ganglia was perturbed by wheat germ agglutinin, sacral NCCs stayed on the nerve fibres but their distribution was altered. In a proliferation medium where the fibre extension was delayed, many sacral NCCs were found outside the fibres, indicating that nerve fibres were permissive but not necessary for sacral NCC migration under this in vitro condition. In conclusion, our results demonstrate that sacral NCCs exhibit migratory behaviours which are distinct from those of vagal NCCs. This work was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project no. CUHK461808). Program/Abstract # 516 Rabconnectin-3a Regulates Vesicle Endocytosis and Canonical Wnt Signaling in Zebrafish Neural Crest Migration Tuttle, Adam M.; Hoffman, Trevor; Schilling, Tom (UC-Irvine, USA) The neural crest (NC) is a population of cells in vertebrates characterized by an epithelial-to-mesenchymal transition (EMT) followed by multiple waves of migration to many parts of the developing embryo and gives rise to several distinct cell lineages. The initiation of NC cell EMT, migration, and path-finding requires a variety of signals, including canonical and non-canonical Wnts, and dynamic regulation of the expression and subcellular localization of cell-cell adhesion molecules, such as Cadherins. Both of these processes can be regulated by controlled endocytosis, lysosomal degradation, and recycling of ligand-receptor complexes and cell-cell adhesion molecules from the plasma membrane of migrating cells. We discovered a gene, rabconnectin-3a (rbcn3a), with novel early NC expression in zebrafish whose knockdown disrupts migration of a subset of NC cells. Our data suggest rbcn3a is required for proper endosomal maturation independent of acidification in NC cells. Maturation and fusion of endosomes is known to regulate signaling pathways, such as Wnt, by aiding in the formation of multivesicular bodies (signalosomes) or contributing to lysosomal degradation of receptors and/or ligands. Knockdown of rbcn3a downregulates direct canonical Wnt targets necessary for NC EMT and migration during a critical time period in NC development. Furthermore, rbcn3a-deficient NC cells that fail to migrate differentiate into pigment progenitors and display aberrantly high levels of Wnt receptor at the membrane with corresponding high levels of canonical Wnt signaling at later developmental stages. We propose a novel developmental role for Rbcn3a in EMT of the NC, in which it acts, at least in part, through its regulation of Wnt signaling in both pre- and post-migratory NC cells and its requirement in early endocytosis. Program/Abstract # 517 Hypoxia regulates neural crest migration by promoting Chemotaxis and Epithelial-to-Mesenchymal-Transition Barriga, Elias (Univ Andres Bello, Chile); Maxwell, Patrick H. (University College of London, UK); Reyes, Ariel E (Univ Andrés, Santiago, Chile); Mayor, Roberto (University College of London, UK) 148
Hypoxia-inducible factors (HIFs) are essential in response to hypoxia. in vitro assays have show that HIF-1 directly regulates key regulators of cancer cell progression and migration, as these factors are also expressed during normal embryonic development we decided to test whether Hif-1α was required for these process. We focused our attention on the development of the neural crest, a highly migratory embryonic cell population. Inhibition of Hif-1α by antisense morpholinos in Xenopus or zebrafish embryos led to complete inhibition of neural crest migration. Our data show that Hif-1α controls the expression of Twist, which in turn represses E- cadherin during epithelial-to-mesenchymal transition (EMT) of neural crest cells. Thus, Hif-1α allows cells to initiate migration by promoting the release of cell-cell adhesions. Additionally, Hif-1α controls chemotaxis towards the chemokine SDF-1 by regulating expression of its receptor Cxcr4. Our results point to Hif-1α as a novel and key regulator that integrates EMT and chemotaxis during migration of neural crest cells. Program/Abstract # 518 Hox genes control cell migration in the lateral line primordium and regulate expression of chemokine receptors downstream of Wnt signalling Xu, Qiling; Breau, Marie A; Wilkinson, David G (MRC Nat Inst for Med Res, UK) Collective cell migration, in which cells retain contacts with each other and move as a coherent assembly, is a crucial aspect of embryo development, tissue repair and cancer metastasis. An amenable model to study this process is the development of the posterior lateral line in zebrafish, which is formed by a cohesive primordium that migrates from head to tail and deposits clusters of cells at intervals that later differentiate to form the mechnosensory neuromasts. The directional migration is guided by the chemokine, Sdf1a, expressed along the path and two chemokine receptors Cxcr4b and Cxcr7b, expressed in different regions within the lateral line primordium. Localized Wnt signaling in the leading part of the primordium controls migration by regulating spatial expression of the chemokine receptors, but the downstream effector(s) mediating this process is not known. We report the identification of Hoxb8a as a critical component of the network required for correct migration of the primordium. We show that Wnt pathway activity is required for Hoxb8a expression in the leading zone, which in turn controls the spatially restricted distribution of Cxcr4b and Cxcr7b. Our work has unraveled new functional links between Wnt, Cxcr4/Cxcr7 and Hox transcription factors, which are involved in many processes during embryo development and in cancers such as myeloid leukemia. Program/Abstract # 519 Fgf signaling is required for proper cell convergence during pectoral limb bud formation Stinnett, Haley K; Mao, Qiyan; Ho, Robert K (U Chicago, USA) The zebrafish limb bud provides an excellent system to explore the genetic basis of coordinated cell behaviors underlying organ morphogenesis. Previous work in our laboratory has demonstrated that zebrafish limb progenitors undergo spatio-topic convergence along the AP axis during pectoral limb bud initiation. Fgf24, a zebrafish fibroblast growth factor, is required for limb progenitor convergence, as limb progenitors fail to converge in Fgf24 morphants. Based on the function and expression pattern of Fgf24 in the limb field, we hypothesize that Fgf24 supplies a convergence cue for oriented limb progenitor migration. However, as Fgf24 is expressed at several stages throughout the limb progenitor lineage (gastrulation, limb field progenitor convergence and subsequent limb outgrowth), it is not clear whether the Fgf24 morphant phenotype reflects the critical function of Fgf24 during limb field progenitor convergence. In this study, we sought to determine if Fgf signaling is required specifically during the period of limb field convergence. Using the FGF receptor inhibitor SU5402, we inhibited Fgf signaling immediately prior to limb field migration and used 4D live imaging to extensively quantify the resulting cell movements. Our results show that Fgf signaling is required during the limb field convergence period for proper cell migration, and suggest that Fgf24 is a candidate for a convergence cue in the lateral plate mesoderm. Program/Abstract # 520 Long-distance cell migrations during larval development in the appendicularian, Oikopleura dioica. Nishida, Hiroki; Kishi, Kanae; Onuma, Takeshi (Osaka U, Japan) The appendicularian, Oikopleura dioica, is a planktonic tunicate (urochodate). Its simple and transparent body, invariant cell lineages, and short life cycle of five days make it as a promising new model system of chordates development. Cleavage pattern, cell lineages and morphogenesis during embryogenesis of three hours are well described. While little information is available on larval development of seven hours after hatching. In this study, morphogenetic movements during larval development of O. dioica were investigated. Organogenesis is completed in 10 hours post fertilization (hpf) and fully functional adult-type body is formed. Timelapse microscopy of developing larvae with aid of fluorescent labeling of nuclei visualized an orchestrated organogenesis. We also traced eventual fates of migrating cells using photoconvertible fluorescent protein, Kaede. There are three cell populations that exhibit directional and long-distance migration: (i) Four oral gland cell precursors at the posterior trunk region migrate to vicinity of the mouth by 7 hpf; (ii) Endodermal strand cells in the tail are retracted into the trunk by 5.5 hpf and give rise to digestive organs; (iii) Two subchordal cell precursors in the trunk migrate posteriorly to tip of the tail. The migration of subchordal cells starts when all of the endodermal strand cells enter into the trunk, and follow the same way but in the opposite direction. These well-defined movements of precursor cells would provide us with opportunities to analyze mechanisms underlying cell migration in this transparent larva of the model system of chordates. 149
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International Society of Developmen
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neural crest cells (hNCC)) human em
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activity may determine the orientat
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Developmental cell signaling pathwa
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opposed roles during early gastrula
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functions by the recruitment of add
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function validated with explant stu
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Program/Abstract # 48 Modeling regu
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surface of the embryo. In zebrafish
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morphologies. Our analyses not only
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junctional proteins (RPE patterning
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Program/Abstract # 78 In vivo recep
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Program/Abstract # 85 Guts and gast
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Program/Abstract # 92 The C. elegan
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Program/Abstract # 98 A gradient of
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Program/Abstract # 106 Developing a
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NSCs, but not in neurons, bind not
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abnormalities in the development of
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Tbx4 and contributes to Tbx4 repres
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downregulated by polycomb-group pro
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Zac1 expression in the developing c
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understanding the mechanisms that u
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Program/Abstract # 156 Systematic I
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Program/Abstract # 163 Size regulat
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TACC3 was localized around the DNA
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Penaeid shrimp represent an importa
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tubule. Using live imaging of cultu
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show that cell polarity is disrupte
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process. However, a clear mechanist
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Zhang, Haoran; Wong, Elaine Yee-man
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condition. Kanyon embryos have a mi
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Program/Abstract # 218 Lfng regulat
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works in concert with basal cues fr
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medaka genome. These miRs are encod
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facilitan cambio en patrón morfoge
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coordinately regulate the expressio
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downstream asymmetric signals. The
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viability and morphology of over 20
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owser. The genomic differences obse
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evolutionary analysis to study the
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teleostei. Our data evidenced that
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ontogeny. The typical condition for
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examples whose Shh expression requi
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insights into the ancestral role of
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Program/Abstract # 308 Mechanistic
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Patients with Joubert Syndrome and
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Program/Abstract # 323 Drosophila g
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signalling during gut and enteric n
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Page 133 and 134: Program/Abstract # 462 Retinaldehyd
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Page 153 and 154: Program/Abstract # 530 The MADS pro
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Page 163 and 164: Program/Abstract # 564 Withdrawn Pr
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Congress Abstracts - Society for Developmental Biology

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