Abstracts - Society for Developmental Biology

19
Dominguez-Castellano, Maria; Garelli, Andres; Gontijo, Alisson; Miguela, Veronica; Caparros, Esther (Inst Neuroci
Alicante, Spain)
Animal size is amazingly constant within species and this constancy is even more striking when we consider the
coincidence in size of the left and right sides of bilaterian organisms. To attain such precision, growing organs must be
capable to sense and communicate their growth to other organs in the organism and to have flexibility to adjust their
growth programmes and the timing of maturation to repair disturbances during ontogeny. How they do so remains a
mystery. We have addressed this issue in the imaginal discs of the fruit fly Drosophila melanogaster, which are known to
have a remarkable flexibility to regulate their size, particularly when they suffer lesions. I will present the findings that
growing imaginal discs produce, and secrete to the hemolymph, a novel insulin/relaxin-like peptide that mediates the
plasticity of growth and maturation that ensures the proper final size,proportions, and the symmetry between the two sides.
Program/Abstract # 58
!): Trying to fathom the mechanisms of planar cell polarity.
Lawrence, Peter, University of Cambridge, United Kingdom
In the past 100 years or more of developmental biology, the significance of vectorial information has often been
overlooked, yet an individual cell cannot contribute properly to building an animal without information both of its position
(that relates to its identity) but also its orientation within the whole. For example, it needs to know which orientation to
divide, which route to move, which direction to send an axon or outgrowth etc. These properties of polarity have lately
become known as planar cell polarity (PCP). I first came across PCP as a graduate student exactly 50 years ago. After
having done some work on this problem for a few years, I then dropped it until about 1995 when I returned to it 100%.
Since then I have been collaborating with José Casal (Cambridge, UK) and Gary Struhl (Columbia, NY) to research the
mechanism of PCP using mostly genetic methods (particularly mosaics) with Drosophila. We are unconventional in that
we are all 3 doing only research and all of us are aged over 50. I will tell the story of what we have discovered and how we
have approached this deep and fascinating problem. Our main findings have been concerned with the functions of three
cadherin proteins, Flamingo (aka Starry Night), Dachsous, and Fat. The former protein works with Frizzled and Van Gogh
within one pathway and the latter two work together with Four-jointed and Dachs in a second independent pathway. Both
pathways help determine the polarity of cells in the epidermis. In both these pathways, polarity information is transferred
from cell to cell via cadherin proteins that constitute molecular bridges. These processes appear to be conserved to
vertebrates.
Program/Abstract # 59
Tissue specific analysis of chromatin identifies temporal enhancer activity in Drosophila mesoderm development
Zinzen, Robert P.; Bonn, Stefan; Girardot, Charles; Perez-Gonzalez, Alexis; Delhomme, Nicolas; Wilczynski, Bartek;
Riddell, Andrew; Furlong, Eileen E.E., EMBL, Heidelberg, Germany
Epigenetic histone modifications and genome-wide binding profiles of general transcription factors can serve as reliable,
global read-outs for the regulatory state of genes and enhancers. A challenge in a developmental context, however, has
been that such features are generally employed throughout the developing embryo. Therefore, whole-embryo studies can
only yield non-specific data from multiple tissues and cell types where any informative signatures are diluted and
contradicting data from diverse tissues is superimposed. We have developed a new method to batch-isolate tissue-specific
chromatin followed by immunoprecipitation (BiTS-ChIP) and have applied this method to the developing Drosophila
embryo by extracting mesoderm-specific signatures for histone modifications and Pol II positioning. The tissue-specific
data is of high sensitivity and specificity and reveals that enhancers exhibit heterogeneous chromatin/Pol II states and that
specific states are highly correlated with spatio-temporal enhancer activity. Though H3K4me1 enrichment generally marks
enhancers, it provides no information on the activity state of regulatory regions; however, other features such as H3K27ac,
H3K79me3 and especially Pol II enrichment clearly mark active enhancers with temporal precision. In a machine-learning
approach based on the uncovered enhancer signatures, we were able to faithfully identify new enhancers that direct spatiotemporal
activity as predicted. Such cell type-specific data can therefore identify enhancers in active use during
development, which will be instrumental in deciphering cis-regulatory networks. Furthermore, our BiTS method should be
widely applicable and easily adaptable toother tissues and animals.
Program/Abstract # 60
Regulatory Genomics in Drosophila
Stark, Alex, IMP-Vienna, Austria
During animal development, the transcription of genes is tightly controlled in a temporal and spatial fashion by cisregulatory
modules (CRMs) or enhancers. Enhancers are DNA elements that contain sequence motifs for specific