Abstracts - Society for Developmental Biology

132
Program/Abstract # 398
From signals to shapes in tissue morphogenesis
Shvartsman, Stas, Princeton University, United States
The epithelial sheet that envelops the Drosophila oocyte gives rise to the eggshell, a complex structure that controls
several critical aspects of embryonic development. Eggshell morphogenesis can be viewed as a two-step process, in which
localized chemical cues induce highly robust tissue deformations. In the first step, a small set of signals establish twodimensional
expression domains of dozens of genes, which collectively control mechanical forces and properties of cells
across the epithelium. In the second step, these forces act on the epithelium, transforming it into a three-dimensional
structure. The anatomical simplicity of the developing egg makes it an ideal system for establishing multiscale models of
epithelial morphogenesis. I will present the results of our efforts to develop and experimentally test quantitative
descriptions of eggshell morphogenesis, starting from network biology of gene expression and then moving to
biomechanical models of tissue deformations.
Program/Abstract # 399
The enhancer disruption (ED) screen in zebrafish.
Villar-Cerviño, Verona; Molano-Mazón, Manuel (U Miguel Hernandez, Spain); Catchpole, Timothy (UTSW Med Ctr);
Valdeolmillos, Miguel (U Miguel Hernandez, Spain); Henkemeyer, Mark (UTSW Med Ctr); Martínez, Luis M.; Borrell,
Víctor; Marín, Oscar (U Miguel Hernandez, Spain).
Transposon-mediated enhancer trap screens in zebrafish have been reported as an effective way to screen for new genes
involved in early developmental processes. Although this approach is well suited for the creation of gene reporter lines, it
is relatively inefficient for the generation of mutations. Insulator sequences have been identified which can block
transcription due to their interference with enhancer activity. We have exploited such insulating activity to build an
innovative enhancer trap vector, based on the Tol2 transposon, whose mutagenic potential has been greatly enhanced by
including an insulator sequence. As a classical enhancer trap, this tool is able to uncover genes with tissue-specific
expression patterns and permit the isolation of their respective reporter lines. Moreover, due to its insulator activity, this
transposon is also able to generate regulatory mutations through the disruption of tissue-specific enhancer activity.
Additionally, we have incorporated the ability to discriminate between 5´and 3´enhancer activity relative to the
transposon’s insertion point. Here we will present results of a genetic screen performed with this tool which we refer to as
an Enhancer Disruption (ED) vector and will discuss its efficient mutagenic activity and its impact in genomic regulatory
landscapes.
Program/Abstract # 400
Cellular tiling in the cerebral cortex through contact repulsion
Bessa, José; Luengo, Mario; Rivero-Gil, Solangel; Ariza-Cosano, Ana; Naranjo, Silvia; Campaña, Francisco;
Caballero, Pablo; Gómez-Skarmeta, José Luis, Centro Andaluz de Biología del Desarrollo, Spain
Cajal-Retzius (CR) cells play a fundamental role in the development of the mammalian cerebral cortex. They control the
formation of cortical layers by regulating the migration of pyramidal cells through the release of Reelin. The function of
CR cells critically depends on their disposition throughout the surface of the cortex, but little is known about the events
controlling this phenomenon. We found that migrating CR cells repel each other upon contact, which leads to their random
dispersion throughout the cortical surface and to the formation of a dynamically stable pattern of distribution that optimizes
surface coverage. This process of cellular tiling is mediated by bi-directional Eph/ephrin interactions. Our observations
reveal a novel mechanism that controls the even distribution of neurons in the developing brain.
Program/Abstract # 401
Capicua regulates proliferation and survival of RB-deficient cells in Drosophila.
Krivy, Kate; Bradley-Gill, Mary-Rose; Moon, Nam, McGill University, Montreal, Canada
Mutations of rbf1, the Drosophila homolog of the RB tumour suppressor gene, generate defects in cell cycle control,
differentiation and cell death during development. Previous studies have established that EGFR/Ras activity is an
important determinant of proliferation and survival of rbf1 deficient cells. Here, we report that Capicua (Cic), an HMG
box transcription factor whose activity is regulated by the EGFR/Ras pathway, regulates both survival and proliferation of
rbf1 mutant cells. We demonstrate that cic mutations allow rbf1 mutant cells to bypass developmentally controlled cell
cycle arrest and apoptotic pressure. The cooperative effect between Cic and RBF1 in promoting G1 arrest is mediated, at
least in part, by limiting Cyclin E expression. Surprisingly, we also found evidence to suggest that cic mutant cells have
decreased levels of Reactive Oxygen Species (ROS), and that the survival of rbf1 mutant cells are affected by changes in