Abstracts - Society for Developmental Biology

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evolutionary history of these species. DNA sequence analysis suggests that these enhancers have changed their genomic
position as the result of the gain and loss of individual transcription factor binding sites rather than large duplications or
translocations. To better understand the molecular mechanisms responsible for the observed changes in cis-regulatory
architecture, we performed a yeast one-hybrid screen testing ~700 transcription factors individually for their ability to bind
to each enhancer sequence. Results from this work will be presented and discussed.
Program/Abstract # 48
The mutations, molecular mechanisms, and constraints directing the evolution of a Drosophila cis-regulatory
element
Rogers, William; Salomone, Joseph; Tacy, David; Williams, Thomas, University of Dayton, United States
A major goal of evolutionary developmental biology research is to illuminate how evolution acts on development to cause
phenotypic change. A wealth of data implicates changes in gene expression as the predominant means by which
morphological traits evolve, and likely via mutations in cis-regulatory elements (CREs) that specify gene expression
patterns. Each expression pattern is encoded in a CRE as a regulatory logic comprised of a collection and organization of
binding sites for certain transcription factor (TF) proteins. While several case studies have identified instances of CRE
evolution, how encoded regulatory logics evolve remains poorly understood. An intraspecific comparison of Drosophila
melanogaster sexually dimorphic abdominal pigmentation patterns presents an opportune situation to reveal how
regulatory logics evolve. The degree of female pigmentation varies between populations and this variation stems from
genetic variation at the bric-à-brac (bab) locus, which encodes the Bab TF proteins that act as repressors of pigmentation
development. Bab expression in females is controlled by a CRE known as the dimorphic element. We identified four
dimorphic element alleles that possess different gene regulatory capabilities. By determining the sequence and function of
the CRE possessed by the most recent common ancestor of these extant populations we were able demonstrate how few
mutations were necessary and sufficient to alter the function of the derived alleles. Ongoing studies seek to reveal how
these few mutations of a relatively large effect modify an ancestral regulatory logic.
Program/Abstract # 49
A comparative transcriptomic analysis reveals conserved features of stem cell pluripotency in planarians and
mammals
Pearson, Bret; Labbe, Roselyne (Hosp for Sick Children/U Toronto, Canada); Irimia, Manuel; Blencowe, Ben (Donnelly
Centre, Canada)
Many long-lived species of animals maintain and require the function of adult stem cells. However, the transcriptomes of
stem cells in invertebrates and vertebrates have not been compared, and consequently ancestral regulatory circuits that
control stem cell populations are poorly defined. In this study, we have used data from high-throughput RNA sequencing
(RNA-Seq) to compare the transcriptomes of highly purified populations of adult pluripotent stem cells from planarians
with the transcriptomes of human and mouse embryonic stem cells. From a stringently-defined set of 4,432, orthologs
shared between planarians, mice and humans, we identified 123 conserved genes that are specifically up-regulated in stem
cells from all three species, and many of which have not been previously implicated in stem cell biology. Guided by this
gene set, we used RNAi screening in planarians to discover novel stem cell regulators,including THADA, PSD12, RAN,
and CBX3, which affected stem cell-associated functions including tissue homeostasis, regeneration, and stem cell
maintenance. Our analysis demonstrates that comparing stem cell transcriptomes from diverse species represents a
powerful approach for identifying conserved genes that function in stem cell biology. These results provide insight into
which genes and associated functions may represent part of the ancestral circuitry underlying the control of stem cell selfrenewal
and pluripotency.
Program/Abstract # 50
Coordinated programs of cell growth and transcriptional regulation in lizard tail regeneration
Hutchins, Elizabeth D.; George, Rajani; Markov, Glenn; Eckalbar, Walter; Geiger, Lauren; DeNardo, Dale (Arizona
State U, Tempe, United States); Fisher, Rebecca (U Arizona College of Medicine, Tempe, United States); Rawls, Alan
(Arizona State U, Tempe, United States); Huentelman, Matthew (Translational Genomics Res Inst); Wilson-Rawls,
Jeanne; Kusumi, Kenro (Arizona State U, Tempe, United States)
Uniquely among amniote vertebrates, lizards can lose their tails and regrow a functional replacement. These regenerated
tails contain newly formed hyaline cartilage, spinal cord, muscle, and skin. Progress in studying the cellular and molecular
mechanisms of lizard regeneration has been limited by lack of genomic resources. However, with the release of the genome
of the green anole, Anolis carolinensis, we have a unique opportunity to identify the cells and pathways activated in lizard
regeneration. Building on our new RNA-Seq based gene annotation, we have quantified the gene expression levels along