Congress Abstracts - Society for Developmental Biology

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around the vertebrate phylotypic period, rather than at later stages that show the amniote-common pattern. Wnt5a expression was found in the growth zone of the dorsal shell, supporting the possible co-option of limb-associated Wnt signaling in the acquisition of this turtle-specific novelty. Our results suggest that turtle evolution was accompanied with an unexpectedly conservative vertebrate phylotypic period, followed by manifestation of their evolutionary novelty. Program/Abstract # 44 Withdrawn Program/Abstract # 45 Transcriptional inputs and outputs of reiterative beta-catenin switches in a spiral-cleaving embryo Stephan Schneider, Benjamin Bastin, Margaret Pruitt, Edward Letcher, Hsien-chao Chou (Iowa St U, USA) In the spiralian annelid Platynereis dumerilii each embryonic cell division oriented along the animal-vegetal axis is accompanied by higher nuclear accumulation of beta-catenin in the vegetal-pole daughter cell. As in the distantly related C. elegans where the Wnt/beta-catenin pathway is activated after every anterior-posterior oriented cell division, these observed reiterative asymmetries appear to convey lineage specific cell fate decisions. Ectopic activation of beta-catenin in animal-pole daughters causes the animalpole daughter cell to adopt the fate of its vegetal-pole daughter cell. However, in contrast to the highly derived Wnt/beta-catenin activation mechanism in C.elegans, individual components of the Wnt/beta-catenin signal transduction pathways are highly conserved in Platynereis. To gain insights into mechanism and contribution of reiterative beta-catenin asymmetries to segregate cell fates in a spiral cleaving embryo and the formation of the annelid body plan, we (1) defined the stereotyped sister cell asymmetries (as observed by different cell sizes, cell cycle times, and beta-catenin activation patterns) in each cell division cycle until the 220 cell stage, (2) deployed a variety of RNA-seq based approaches to identify genes that comprise the reiterative Wnt/beta-catenin activation mechanisms and potential downstream targets in normal and compromised embryos, and (3) mapped the expression of Wnt pathway components (ligands, receptors, intracellular components, potential target genes) into distinct cell lineages. Our analysis provides the first comprehensive view of spatial and temporal inputs and outputs of Wnt signaling into embryos utilizing a spiral-mode of cell divisions to segregate cell fates. Program/Abstract # 46 Investigating genomic imprinting in the honeybee methylome Robert Drewell (Harvey Mudd College, USA) The Kin Theory of Genomic Imprinting (KTGI) predicts that imprinting will arise when the reproductive interests of parents differ. In colonies of the eusocial honeybee, Apis mellifera, a queen’s interests are maximised if she monopolises reproduction in the colony and all her workers are sterile. Males, in contrast, can increase reproductive success if some of their worker offspring are fertile. Honeybees possess a functional DNA methylation system, and methylation is known to play a role in caste determination. Parent-oforigin specific imprinting via methylation provides a candidate mechanism by which a queen may enforce sterility in her worker offspring; by epigenetically modifying genes required for fertility. We examined the genome-wide methylation profile of unfertilized eggs and sperm. 381 genes show significantly differential methylation, with 80% of these genes more highly methylated in eggs. These extensive methylation differences in the germline provide support for the KTGI, showing that the methylome of reproductive males and females differs. Parentally-directed epigenetic modification of genes related to reproduction may therefore be a key mechanism by which eusociality evolves and is maintained. Program/Abstract # 47 Budgett’s frog: a new vertebrate model for morphogenesis at multiple biological scales Nanette M. Nascone-Yoder, Mandy Womble, Cris Ledon-Rettig, Adam Davis, Mike Dush (North Carolina St U, USA) Complex morphogenetic processes underlie the emergence of biological form but are often challenging to study in existing vertebrate models. To address this issue, we are capitalizing on the unique developmental features of Budgett’s frog, Lepidobatrachus laevis. In addition to the experimental advantages that have made amphibian models invaluable, Lepidobatrachus embryos also possess exceptional features that are especially powerful for investigating morphogenesis. Their extremely rapid development yields a feeding tadpole in less than two days, reducing to hours morphogenetic events that can take several days or weeks to complete in other models. Lepidobatrachus oocytes are eight times the volume of the common laboratory Xenopus laevis. Consequently, the large blastomeres of the late blastula can be injected with gain- and loss-of-function reagents to target very specific tissues with high precision. Moreover, because Lepidobatrachus morphogenesis proceeds at such a large scale, it offers detailed resolution of organogenesis at even the subcellular level. The remarkable size also enables transcriptional profiling of highly spatiotemporallydefined, universally-applicable morphogenetic events such as tissue folding or organ looping. Finally, Lepidobatrachus tadpoles exhibit specializations adapted for a carnivorous diet that provide a new inroad for uncovering the developmental changes that generate phenotypic variation during evolution. Comparative chemical genetic screens can be used to implicate defined molecular pathways and morphogenetic processes in the origin of such novelties. The inimitable features of Lepidobatrachus promise to provide an integrated view of morphogenesis at multiple biological scales. 14
Program/Abstract # 48 Modeling regulatory systems for sea urchin development Isabelle Peter, Eric Davidson (Caltech, USA) The formation of distinct cell fate specification domains occurs by means of spatial control of gene expression. At the system level, gene regulatory network (GRN) models attempt to incorporate the complete gene regulatory apparatus which determines a specific developmental process. Yet as these network models include an increasing number of regulatory genes, the outcome of the regulatory interactions between them becomes less easily comprehensible. The sea urchin endomesoderm GRN consists of about 50 regulatory genes and determines the formation of at least five different gene expression domains before the onset of gastrulation. A recently developed Boolean model demonstrates that the experimentally established regulatory interactions which constitute the endomesoderm GRN model are indeed largely sufficient to reconstruct the spatial and temporal regulatory gene expression patterns observed during the first thirty hours of sea urchin development. Furthermore, perturbation of the Boolean model accurately predicted the outcome of experimental perturbation. The Boolean model thus shows that GRN models are in principle sufficient to explain progressive regulatory gene expression during development and it contributes to the formalization of regulatory processes. The insights gained from this analysis are now being applied to a much more complex process of post-gastrular organogenesis, the formation of the embryonic gut. Program/Abstract # 49 A gene regulatory network for endomesodermal specification in a basal deuterostome. Veronica Frances Hinman, Brenna McMauley (Carnegie Mellon, USA) A central pursuit in developmental biology is to understand how maternal processes can generate an embryo with molecularly distinct cell populations. A causal explanation for this requires a comprehensive gene regulatory network (GRN) model that can explain how genes are expressed at exactly the right time and in the right cells. We will discuss our recent work that describes the GRN for one of the most important events in early development, the specification and segregation endoderm and mesoderm, using the sea star, Patiria miniata, as our model system . Sea stars are a class of Echinoderms that are considered to represent the basal mode of development of this phylum and possibly of all deuterostomes. The simplicity of sea star early development allows us to provide a detailed explanation of endomesderm specification. Sea stars undergo equal cleavage and generate a holoblastula of only several hundred cells. Endomesoderm fated cells form at the vegetal pole of the early embryo. Later mesoderm fated cells will segregate as central population surrounded by a torus of endoderm. We show that this process is regulated by a spatio temporal gradient of nuclear β catenin. A maternally controlled transcriptional factor based GRN additionally provides timing control for gene activation to ensure a robust response to nuclear β catenin. We will also discuss how these GRN topologies can evolve by altering the β catenin gradient and other signaling pathways. Program/Abstract # 50 Gene regulatory network of neural crest development Maneeshi Prasad, (Northwestern, USA) The Neural Crest (NC) is an embryonic stem cell population that is induced at the neural plate border in vertebrates and later emigrates from the dorsal aspect of the developing neural tube, migrate extensively, and give rise to a large and diverse group of cell types. A network of signaling pathways and transcription factors form the neural crest gene regulatory network (NC-GRN) that regulates the induction, specification and migration of NC. These signaling gradients from the neural and non-neural ectoderm, and mesoderm in the form of Wnt and BMP antagonists induce the expression of early neural crest specifiers, Snail, Twist and Sox9. But not much is known about the downstream targets of these neural crest specifiers and their role during different stages of NC development. However, the reiterative use of these factors during different stages of neural crest development suggests their role in regulating different target genes in a temporally controlled manner. To better understand their role in NC-GRN it is essential to decipher their targets during different stages of NC development. Using genome wide approaches such as ChIP-Seq and RNA-Seq, we have identified new putative regulatory targets of these neural crest specifiers during premigratory stages of neural crest development in Xenopus laevis embryos. These targets include genes involved in regulating EMT as well as maintaining stem cell state. We confirmed the presence of known targets of these factors and also new putative targets that are involved in induction and migration stages of NC development. These Sox9 and Twist targets will provide more insights into the role of these NC specifiers during different stages of NC development and also elaborate their role in NC-GRN. Program/Abstract # 51 The phosphorylation state of Drosophila Mad determines its choice between BMP and Wingless signaling Edward Eivers, Marlyn Rios, Abigail Aleman, Daniel Lee, Matthew Juarez, Keristineh Vartanpour (CSU Los Angeles, USA) Bone morphogenetic proteins (BMPs) and Wnts are growth factors that are known to regulate a broad range of cellular events such as stem cell maintenance, cell differentiation and organogenesis, while dysfunctional signaling of either pathway can result in severe developmental abnormalities. Here we describe a new molecular mechanism by which the phosphorylation state of the transcription factor Mad determines its ability to transduce either BMP or Wingless (a Wnt ligand) signals in Drosophila cells. Previously, Mad was thought to function in gene transcription only when phosphorylated by the BMP receptor. We now demonstrate that Mad is required for canonical Wingless signaling specifically when in an unphosphorylated state, by forming a Mad-Pangolin-Armadillo Wnt 15
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Page 51 and 52: Penaeid shrimp represent an importa
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Page 63 and 64: 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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normally form, hence producing prox
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survival in Shh mutant embryos foll
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conserved in amniotes other than ch
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maturation and function. We strive
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Urness, Lisa D; Bleyl, Steven B (Un
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development is already unknown. Emb
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in A-P and P-D patterning by establ
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perturbed in arco piccolo mutants w
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Hoxb7-Cre line, leads to multiple u
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differentiation from common progeni
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investigate this issue, we used tar
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stem cell‐like characteristics. H
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diminished. Interestingly, we found
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y invading osteoblasts. Quite diffe
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coimmunoprecipitation experiments d
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cells and sub-cellular endosomal co
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accumulation is decreased. This wor
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Sex determination in vertebrates de
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Program/Abstract # 462 Retinaldehyd
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Program/Abstract # 469 Search for n
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growth factors used to keep them al
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it is still required to promote mig
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on the outside of small clear vesic
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Program/Abstract # 497 mef2ca contr
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were colocalized along the epidermi
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neural tube morphogenesis, is conse
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Hypoxia-inducible factors (HIFs) ar
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To address this issue, we have take
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Program/Abstract # 530 The MADS pro
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Better understanding of the underly
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NPCs blunted proliferation in the S
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Program/Abstract # 551 Evolutionari
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group is interested in inferring an
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Program/Abstract # 564 Withdrawn Pr
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Program/Abstract # 573 Fluoride ind
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oligodendrocytes of the central ner
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cycle, no changes were observed in
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have begun to document the targets
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Congress Abstracts - Society for Developmental Biology

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