Abstracts - Society for Developmental Biology

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paracellular space, and interact with the actin cytoskeleton via adaptor and scaffolding proteins. Here, we report that
Claudin-10 mRNA is asymmetrically expressed on the right side of Hensen’s node, the site where the left-right patterning
cascade is initiated. We demonstrate that overexpression of Claudin-10 on the left side of the node, or knockdown of
endogenous Claudin-10 on the right side of the node, randomizes the direction of heart-looping, the earliest morphological
sign of disrupted left-right patterning. Furthermore, expression of classic left-right patterning genes Pitx2c and cSnR show
altered expressed in manipulated embryos. Our data also show that the PDZ-binding domain of Claudin-10 is required for
its function at the node. These data suggest that asymmetric expression of Claudin-10 at Hensen's node is required for
normal patterning of the left-right axis.
Program/Abstract # 45
The Development and Evolution of Animal Epithelial Barriers
Juarez, Michelle; Kim, Myungjin; Pare, Adam; Patterson, Rachel; McGinnis, Bill, UC San Diego, United States
The Grainy head (GRH) family of transcription factors are crucial for epidermal-barrier development and regeneration in
most or all animals. An important question in regeneration is how transcription factors that program the normal
development and differentiation of tissues are functionally reactivated after body parts are lost or wounded. We found that
GRH is modified by Extracellular signal-Regulated Kinase (ERK) phosphorylation, and this modification is required for
GRH function in the regeneration of an epidermal barrier. However, GRH with mutant ERK phosphorylation sites can still
promote barrier formation during embryonic epidermal development, suggesting that ERK sites are dispensable for the
GRH function in normal development of epidermal barriers. These results provide mechanistic insight into how epidermal
regeneration can be initiated by post-translational modificationof a key transcription factor that normally mediates the
developmental generation of that tissue. Interestingly, proteins in the GRH family are also found in many species of fungi,
organisms that lack epidermal tissues. We show that the Neurospora GRH-like proteinhas a DNA-binding specificity
similar to the animal GRH family proteins. Analysis of the phenotype of Neurospora grhl mutants and the transcriptome of
Drosophila grh and Neurospora grhl mutants suggest the fascinating possibility that the apical extracellular barriers of
some animals share an evolutionary connection with the cell wall of the animal-fungal ancestor, and that the formation of
this ancestral physical barrier was under the control of a transcriptional code that included GRH-like proteins.
Program/Abstract # 46
Evolution of Dact gene family
Sobreira, Debora R., Univ Estadual de Campinas, Brazil; Dietrich, Susanne (Portsmouth, UK); Janousek, Ricardo (Univ
Estadual de Campinas, Brazil); Schubert, Frank (Portsmouth, UK); Alvares, Lucia (Univ Estadual de Campinas, Brazil)
Dact genes form a small gene family of adaptor proteins important to several processes of vertebrates development. Three
Dact genes have been identified in human and mouse, two in chicken, one in frog and two in zebrafish. These proteins play
a wide variety of functions during embryonic development and adulthood by modulating the Wnt and TGF-ß signaling
pathways. However, while the Wnt and TGF-ß signal transduction engines are ancient, being present throughout the animal
kingdom, Dact is one of the very few embryogenesis-coordinator gene families which are restricted to vertebrates and its
origin remains unknown. Moreover, it seems that different vertebrates had recruited a particular set of Dact genes in order
to regulate and possibly integrate differentially Wnt and TGF-ß signals. In order to understand the origin and evolution of
the Dact gene family, in this study we used database mining, phylogenetic, synteny analyses and in situ hybridization
assays. Our phylogenetics analysis revealed an ancestral Dact gene in Branchiostoma floridae’s genome and two new Dact
paralogs (Dact 3 and 4), meaning that a repertoire of four Dact genes is found in vertebrates. The full set of four Dact
genes is present in teleosts, lizards and snakes but not in amphibians, mammals and birds. The Dact loci synteny analyses
corroborate the phylogenetic data and reinforce the hypothesis that the four Dact genes arose from a common ancestral
after successive whole genome duplications invertebrates. Zebrafish in situ hybridization assays were conduced and the
results supported the in silico data.
Program/Abstract # 47
Rapid evolution of cis-regulatory architecture in the Drosophila yellow gene
Kalay, Gizem; Lusk, Richard; Dome, Mackenzie, University of Michigan, Ann Arbor, United States; Deplancke, Bart
(École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland); Wittkopp, Patricia (U Michigan, Ann Arbor, US))
Enhancers control when, where, and how much of a gene is expressed, and evolutionary changes in these sequences are an
important source of phenotypic diversity. To better understand how enhancer sequence and function evolves, we have been
studying the evolution of cis-regulatory architecture in the Drosophila yellow gene. Using reporter genes to functionally
test for tissue-specific enhancer activity in the intronic and 5’ intergenic sequences of the yellow gene from six different
Drosophila species has shown that the genomic locations of tissue-specific enhancers have changed multiple times in the