Basic HTML Version
Poster Full Abstracts - Gametogenesis and Organogenesis
Poster board number is above title. The first author is the presenter
279
and examining the phenotypes of both loss and overexpression at the ultra-structural level. By learning how the USH genes function during the formation of
the relatively simple Drosophila SG and trachea, we expect to gain important insight into how the USH genes function in human development and disease.
550A
A gradient of the transcription factor Cut programs patterning and growth of
Drosophila
airways.
Chrysoula Pitsouli
1
, Norbert Perrimon
1,2
. 1) Dept
Gen, Harvard Med Sch, Boston, MA; 2) HHMI.
A fundamental question in developmental biology is how tissue growth and tissue patterning are coordinately regulated to generate complex organs with
characteristic shapes and sizes. Evolutionarily conserved molecules control either growth or patterning, but few have been shown to coordinate both
processes during organogenesis and their modes of action remain largely unclear. Here we show that in the developing primordium of the
Drosophila
adult
trachea, the homeobox transcription factor Cut regulates both growth and patterning depending on its absolute expression level. We show that Cut is
expressed in a gradient, the low and high expression domain of which defines the zones of highest and lowest proliferation, respectively, while absence of
Cut expression enables the patterning of airway progenitors. The difference in Cut levels orchestrates distinct transcriptional expression programs necessary
for patterning or growth. Furthermore, we show that the Cut gradient is established by the positive and negative actions of the Wnt/Wingless (Wg) and
Notch signaling pathways respectively, which are activated in domains that overlap with the zone of highest cell proliferation. Thus, our study identifies the
transcription factor Cut as a target of the Wg and Notch signals and highlights the importance of its graded expression in the transcriptional programming of
patterning versus growth in a developing epithelial structure.
551B
The dynein motor complex and Whacked RabGAP/Rab35 regulate seamless tube morphogenesis in
Drosophila
terminal cells.
Jodi Schottenfeld,
Amin Ghabrial. Cell & Dev Biol, Univ Pennsylvania, Philadelphia, PA.
The
Drosophila
tracheal system is composed of a network of tubes that forms by specialized tip cells leading the migration of new branches and mediating
their interconnection. Some of these tip cells become specialized “terminal cells” that go on to form branched seamless tubes, unicellular tubes that lack
epithelial junctions, that ramify extensively on target tissues. In the mammalian vascular system, endothelial cells form seamless tubes during angiogenesis.
Very little is known about the apical-basal properties of seamless tubes and the genes required to establish and maintain this polarity. We investigated
terminal cell polarity and found that the lumenal membrane is “apical,” since puncta of the definitive apical membrane marker, Crumbs, decorate the
seamless tube. Actin:GFP outlines this apical membrane and also highlights elaborate filopodia at the tips of growing branches. Microtubules also show
striking polarity in seamless tubes: γ-tubulin, a primary component of the microtubule organizing center, lines the lumenal membrane and is enriched at the
tube tip. Since γ-tubulin marks the site of microtubule nucleation, minus-ends of terminal cell microtubules are directed towards the lumen, thus leading us
to hypothesize that minus-end directed transport along microtubules is required for tube formation. Stable microtubules appear in parallel arrays to the tube,
with thickened microtubule bundles extending past the tube tip, likely laying the foundation for future membrane addition. In support of this hypothesis,
terminal cells mutant for components of the dynein motor complex (
Dhc64c, dlic, Gl
p150
, and
lis-1
) generate extensions that fail to form seamless tubes. In
the absence of tubes, microtubule organization remained intact, indicating a direct role for minus-end directed microtubule transport in seamless tube
formation. In addition, we have identified the Rab35 GAP,
whacked
, as a regulator of polarized growth of seamless tubes and have evidence to suggest that
the Rab35-Whacked pathway promotes apical membrane addition by way of the dynein motor complex.
552C
Src42A
-dependent polarized cell shape changes mediate epithelial tube elongation.
Dominique Foerster, Stefan Luschnig. Institute of Molecular Life
Sciences and PhD Program in Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland.
Epithelial tubes are the basic unit of many organs, such as the mammalian lungs or kidneys. However, the cellular and molecular mechanisms of tube size
control are poorly understood. We performed comprehensive EMS mutagenesis screens to identify new genes involved in tracheal tube development.
Several new loci were found, which affect various morphological features (tube size and shape, branching, lumen fusion), as well as cellular processes, such
as secretion and endocytosis. While many genes are required to limit tracheal tube elongation, we found only one gene to be required for tube elongation.
We identified new mutations in the tyrosine kinase Src42A that result in tube elongation defects. Multicolor cell labelling and 3D image analysis revealed
that this phenotype is caused by a change in epithelial organization and tracheal cell shapes. While wild-type tracheal cells form a simple columnar
epithelium and expand along the tube axis during tube elongation,
Src42A
mutant cells show a pseudostratified organization, and cell bodies elongate
perpendicular to the tube. In contrast, constitutive activation of Src42A induces tube overelongation and cell stretching, indicating that Src42A acts
instructively in this process. E-Cadherin turnover is dramatically reduced in
Src42A
loss-of-function mutants, while constitutively active
Src42A
leads to E-
Cadherin mislocalization. This suggests that Src42A-dependent remodelling of adherens junctions is limiting for the cell shape changes that mediate tube
elongation. Strikingly, Src42A controls tube elongation independently of diametric expansion, which is driven by apical secretion. Thus we defined distinct
cellular processes that independently regulate the dimensions of epithelial tubes.
553A
Orthogonal illumination microscopy live imaging of
Drosophila
embryo.
Dmitri V Novikov
1
, Gordon L Kindlmann
2
, Kevin P White
1
. 1) Institute for
Genomics and Systems Biology, University of Chicago, Chicago, IL; 2) Department of Computer Science, University of Chicago, Chicago, IL.
The IGSB advanced imaging core is using a new, high speed, high resolution DSLM microscope (acquired from E. Stelzer, EMBL) for live imaging of
Drosophila
embryogenesis. We have generated over 50 fly lines with GFP and YFP tagged transcription factors and other developmental molecules that are
expressed in their endogenous patterns. These reagents can be used for both imaging and for chromatin immunopreciptation (K.J. Venken et al., Nat.
Methods, 2009; N. Nègre et al., Nature, 2011). Using orthogonal illumination microscopy and custom image processing software, we are generating a
comprehensive database of 4D gene expression profiles in the fly embryo. To further increase resolution of the acquired images, we modified the protocol
for mounting
Drosophila
embryo in the DSLM specimen chamber, using a new procedure whereby the embryo is attached to a clear polymer plate with an
adhesive surface, eliminating the use of agarose embedding. Here we describe initial results obtained using this system.