Congress Abstracts - Society for Developmental Biology

teleostei. Our data evidenced that the brain asymmetry program has originated in the dorsal diencephalon independently of parapineal
migration and that the laterality imposed by Nodal is an ancestral vertebrate trait.
Program/Abstract # 279
Early, nonciliary role for microtubule proteins in left–right patterning is conserved across kingdoms
Lobikin, Maria (Tufts University, USA); Wang, Gang; Xu, Jingsong (Univ of Illinois College of Medicine, USA); Hsieh, Yi-Wen;
Chuang, Chiou-Fen (Cincinnati Children's Hospital Research Foundation, USA); Lemire, Joan; Levin, Michael (Tufts University,
USA)
Many types of embryos’ bodyplans exhibit consistently oriented laterality of the heart, viscera, and brain. Errors of left–right
patterning present an important class of human birth defects, and considerable controversy exists about the nature and evolutionary
conservation of the molecular mechanisms that allow embryos to reliably orient the left–right axis. We have found that the same
mutations in the cytoskeletal protein tubulin that alter asymmetry in plants also affect very early steps of left–right patterning in
nematode and frog embryos, as well as the chirality of human cells in culture. Our unbiased proteomic analysis identified multiple
maternal proteins that are consistently localized to the left and right of the Xenopus embryo during the first two cleavages. In the frog
embryo, tubulin α and tubulin γ-associated proteins are required for the differential distribution of these maternal proteins to the left or
right blastomere at the first cell division. Our data reveal a remarkably-wide molecular conservation of mechanisms initiating left–
right asymmetry and characterize novel aspects of left-right patterning occurring within the cytoplasm of early blastomeres. The origin
of laterality is intracellular, ancient, and highly conserved across kingdoms - a fundamental feature of the cytoskeleton that underlies
chirality in cells and multicellular organisms.
Program/Abstract # 280
Evolution of Placode-Derived Neurons Assessed by Cell Type-Specific Transcriptional Profiling
Shimeld, Sebastian; Patthey, Cedric (University of Oxford, UK)
A major challenge in understanding the evolution of the vertebrate body plan is to model how gene usage evolved to produce the
cranial placodes from which the paired sensory organs arise. Although our knowledge of placode development is growing, the
function and evolution of the genetic regulatory networks underpinning the specification of differentiated cell types are not well
known. In particular, we lack specific molecular markers for the placode-derived neurons. Combining dissection, FACS sorting and
next-generation sequencing in chicken, we have developed a method for the establishment of cell type-specific transcription profiles in
order to study the evolution and development of sensory neuronal cell types.
Program/Abstract # 281
SeaBase – A new tool to analyze RNAseq data and a big step on our way toward a Nematostella gene interaction network
Fischer, Antje (MBL,USA); Cosentino, Carlo (Università degli Studi Magna Graecia Catanzaro, Italy); Smith, Joel (MBL, USA)
The evolutionary origin of fundamental developmental programs such as axis specification and germ layer specification is still
unsolved. Cnidarians, the sister group of Bilaterians, have a seemingly simpler body plan and form only two embryonic germ layers, a
one-way gut and are traditionally viewed as radial symmetric. Many of the embryonic patterning genes in Bilaterians are present in
Cnidarians with little known about their gene regulatory network (GRN). The sea anemone Nematostella vectensis is a particularly
suitable cnidarian model system. We present our first steps towards resolving the GRN for early development in Nematostella. Using
an Illumina HiSeq to perform quantitative RNA-seq, we established a high-density gene expression time course, from fertilization to
gastrulation. We use SeaBase, a new multispecies web resource for sharing and analyzing RNAseq data, to visualize and compare
absolute transcript levels for each gene. SeaBase is a powerful tool for differential gene expression analysis, between different
developmental stages, perturbations and species. The comparison of gene expression levels will help to determine the statistical
dependencies between all gene pairs, a measure of genetic interaction. The resulting testable network model will offer first insights
into which genes are the most interconnected and thus provide the starting point for detailed network analyses. Comparing the
Nematostella GRN to known interactions in other species will advance our understanding about evolutionary changes of the
developmental GRN across metazoans. To initiate the comparison we are performing quantitative RNA-seq time courses in the snail
Crepidula fornicata and the ctenophore Mnemiopsis leidyi.
Program/Abstract # 282
Evolutionary Origins of the Vertebrate “New Head”
Abitua, Philip; Wagner, Eileen; Levine, Mike (UC Berkeley, USA)
In their classic paper (Science 220, 268-273; 1983) Gans and Northcutt proposed that, “most of the morphological and functional
differences between vertebrates and other chordates occur in the head…”. Several distinctive features of the vertebrates arise from
cranial placodes and a special form of neural crest, the ectomesenchyme, which produces a variety of mesodermal derivatives
including connective, skeletal and muscular tissues. We are using the simple sea squirt, Ciona intestinalis, to investigate the evolution
of these cell types since it is a close relative of the vertebrates. I will provide evidence that the Ciona tadpole contains a cell lineage
that is homologous to neural crest, which can be reprogrammed into “ectomesenchyme” by the misexpression of Twist. Additional
studies suggest that the anterior neural plate border of the Ciona embryo produces GnRH-expressing neurons, which we are studying
to elucidate the origins of the chordate endocrine system.
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