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Poster Full Abstracts - Regulation of Gene Expression
Poster board number is above title. The first author is the presenter
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expression at the anterior tip is visible. The regulatory region of
gt
contains binding sites for the maternal activators Bicoid and Cadual, and repressor sites
for other gap genes, such as Krueppel and Hunchback. Several partially overlapping
cis
-regulatory elements (CRE) for
gt
were previously predicted through
detection of clusters of binding sites. I quantified their expression patterns with a high-throughput method for extracting concentrations from confocal
microscope images. These data will be fed into a mathematical model of transcriptional control in order to predict spatio-temporal expression patterns of
CREs from sequence. The model gives the combinations of binding sites required for correct expression as output. It can predict expression patterns for all
kinds of modifications and combinations within the regulatory regions, and the most interesting ones will then be verified
in vivo
with constructs harbouring
mutations in binding sites, or by testing a CRE in a mutant background lacking a certain transcription factor.
780C
Decoding transcriptional control at the IAB7b
cis
-regulatory module in the bithorax complex.
Jessica S. Kurata, Michael J. Nevarez, Robert A.
Drewell. Harvey Mudd College, Claremont, CA.
The body plan for
Drosophila
is determined in early development by the spatially-regulated expression of homeotic (Hox) genes. This spatial patterning is
itself dictated by the distribution of transcription factors (TFs) in the embryo and controlled primarily through enhancer
cis
-regulatory modules (CRMs). The
330 kb bithorax complex (BX-C) contains three Hox genes: ultrabithorax (
ubx
), abdominal-A (
abd-A
), and Abdominal-B (
Abd-B
). Expression of each gene
in segments along the anteroposterior axis is controlled by CRMs in the neighboring infraabdominal (
iab
) regions.
The IAB7b enhancer is responsible for the expression of
Abd-B
in the seventh abdominal segment (A7) of the
Drosophila
embryo. Investigation of the
IAB7b enhancer has revealed an evolutionarily conserved signature motif, consisting of a cluster of two FUSHI-TARAZU (FTZ) and two KRUPPEL (KR)
TF binding sites. The signature motif, when isolated from the rest of the IAB7b enhancer, drives reporter gene expression in A5, A7, and A9. We examined
the role of the transcriptional repressor KNIRPS in restricting the IAB7b-directed expression pattern and investigated the functional importance of spacing
between the two FTZ sites.
781A
Spatial regulation of
achaete
via global activation and repression by Hairy and Delta.
Ji Inn Lee, Meghana Joshi, Teresa Orenic. Dept Biological Sci,
Univ Illinois, Chicago, Chicago, IL.
During vertebrate and invertebrate development, organs and tissues must be precisely patterned and periodic proneural gene expression is an early and
essential event in neuronal pattern formation. The
Drosophila melanogaster
sensory bristles are a good model system to study the molecular mechanisms
involved in the precise proneural gene expression. There are two classes of sensory bristles: early specified (mechanosensory macrochaetae and
chemosensory microchaetae) and late specified (mechanosensory microchaetae) bristles. Previous studies suggest that patterning of early specified bristles
requires induction of the proneural gene expression at specific epidermal locations: proneural gene expression in primordia of early specified bristles is
controlled by discrete modular
cis
-regulatory elements (CRE) (Campuzano and Modolell 1992; Gomez-Skarmeta et al., 2003). Our studies, however,
suggest that a different mechanism is used to pattern late specified bristles: expression of proneural gene
achaete
(
ac
) in primordia of late specified bristles is
controlled by a single CRE. On the surface of the
Drosophila
leg, small mechanosensory microchaetae (mC) are organized in a series of longitudinal rows
along the leg circumference. In the prepupal leg,
ac
is expressed in longitudinal stripes which comprise the leg microchaete primordia. We have found that
Hairy (H) and Delta (Dl) function concertedly and non-redundantly to define periodic
ac
expression. This process involves broad and late activation of
ac
expression and refinement in response to a prepattern of repression, which is established by Hairy and Delta. These findings have allowed us to formulate a
general model for generation of periodic bristle patterns in the adult leg and this model is supported by the analysis of a CRE that specifically directs
ac
expression in the leg proneural fields. This CRE contains an activation element, which directs broad expression of
ac
along the circumference of prepupal
legs, and repression elements, which are Dl/N and Hairy responsive.
782B
A post-blastoderm role of Zelda as regulator of CNS midline and tracheal gene expression.
Joseph C. Pearson, Joseph D. Watson, Stephen T. Crews.
Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC.
Changes in
cis
-regulatory sequences such as enhancers have been proposed as an important force of evolutionary change. One mechanism by which
cis
-
regulatory evolution can occur involves developing redundant mechanisms, using different regulators, to control a gene's expression. This redundancy allows
flexibility in subsequent gain or loss of individual binding sites. We have identified a 285 b.p. enhancer controlling all embryonic expression of
CG13333
,
including in midline glia and tracheal primordia. The pattern controlled by the
CG13333
enhancer resembles patterns controlled by enhancers regulated by
the bHLH-PAS transcription factors Single-minded (Sim) and Trachealess (Trh). However, mutating the Sim/Trh consensus site did not significantly alter
midline or tracheal expression. Instead, a set of four sequences (T1-4, consensus AGGTA/GG) were required for this and other
CG13333
expression. These
sequences resemble binding sites for the transcription factor Zelda (Zld), a master regulator of transcription at the maternal-to-zygotic transition.
CG13333
expression was lost in
zld
mutants, and ChIP-Seq has demonstrated Zld binding to this enhancer at blastoderm stage (Harrison et al., 2011, PLoS Genetics).
While some aspects of
CG13333
expression were eliminated by mutation of high-affinity Zld binding sites (sites T1 and T3), midline and tracheal
expression was maintained. In contrast, mutating sites T1, T3, as well as a third site that diverges from the optimal Zld binding site (T4), eliminated midline
and drastically reduced tracheal expression. Similarly, mutating high-affinity Zld sites T1 and T3 as well as the Sim/Trh site essentially eliminated midline
and tracheal expression. Thus, both Zld and Sim/Trh directly regulate
CG13333
expression in CNS midline and tracheal cells. Surprisingly, prominent
midline expression of
CG13333
is unique to
D. melanogaster
, although both
zld
and Sim are expressed in midline cells in all
Drosophila
species; we are
testing whether the
D. melanogaster CG13333
midline expression is due to changes in
CG13333
sequences or an upstream regulator.
783C
Distinct transcription factor binding strategies at the intersection of growth and patterning in the Hippo signaling pathway.
Matthew Slattery
1,2
,
Roumen Voutev
2
, Lijia Ma
1
, Nicolas Negre
1
, Kevin White
1
, Richard Mann
2
. 1) Institute for Genomics and Systems Biology, University of Chicago,
Chicago, IL; 2) Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY.
The Hippo pathway has recently emerged as a key regulator of cellular proliferation in both invertebrates and mammals. A downstream effector of the