Congress Abstracts - Society for Developmental Biology

Antoine Zalc, Revital Rattenbach, Frédéric Relaix (UPMC-Paris, France)
Exposure to environmental pollutants, such as Dioxins, during pregnancy leads to teratogenic defects. It was shown that exposure to
TCDD (2,3,7,8-Tetrachlorodibenzo-p-dioxin) can cause reproductive and developmental defects such as craniofacial malformations.
However the molecular link between these teratogenic compounds and developmental pathways remain poorly understood. Here we
show that mice deficient for Pax3 and Pax7, two related paired-homeobox transcription factors essential for neural crest cells
development, display severe craniofacial defects. We identified downstream molecular pathways linked with Pax3/7 function in
craniofacial morphogenesis. Strikingly, w e have demonstrated that not only impairment in the functions of these proteins leads to the
formation of facial clefts reminiscent of that seen upon TCDD exposure, but also that these defects are mediated by ectopic activation
of the Aryl Hydrocarbon Receptor ( AhR) signalling , the receptor to TCDD. Importantly, we show that blocking AhR function
rescues facial closure in Pax3/7-deficient embryos. These results demonstrate that Pax3 and Pax7 have a novel and unexpected role in
regulating environmental stress response pathways during development.
Program/Abstract # 74
The molecular basis of development and diversification of beetle horns.
Teiya Kijimoto, Armin Moczek (Indiana U, USA)
One of the most fascinating themes in evolutionary developmental biology is the molecular and developmental basis of diversity in
form and shape. Horned beetles in general, and the genus Onthophagus in particular, provide excellent opportunities to address this
fundamental question given the dramatic diversity that exists both within and between species in important aspects of horn
development, including location, number, size, and shape of horns. Since beetle horns do not share obvious homology with traditional
insect structures, they offer additional opportunities to investigate the development and evolution of a novel trait. Lastly, many aspects
of horn development are influenced variably by both genetic and environmental factors (in particular nutrition), thus making horns
useful traits with which to explore the developmental basis of plasticity. Here we report on the role of sex-determination and
appendage patterning genes, and their potential interplay, in the regulation of shape and size of beetle horns. Specifically, (i) we show
that sex determination gene doublesex (dsx) plays a fundamental role in sex- as well as nutrition-dependent horn development and its
diversification, including the secondary loss of plasticity and the rapid evolution of reversed sexual dimorphism (Kijimoto et al. 2012).
(ii) Second, we present our most recent findings on patterning genes that specify important aspects of horn development, and whose
activation may be regulated at least in part by dsx. We discuss the most important implications of our results for our understanding of
the regulation and diversification of shape and the role of cooption in evolutionary innovation.
Program/Abstract #75
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Program/Abstract # 76
Changing the way we teach: how we should and why we must! (Viktor Hamburger Prize Lecture)
Bill Wood (U Colorado-Boulder, USA)
Several efforts over the past decade have sought to increase the use of research-based pedagogy in college-level biology courses.
Although the resulting movement toward a more scientific approach to teaching is slowly gaining ground, change is difficult; there is
still a long way to go, and time may be running out. If we cannot increase the added value of the residential college experience by
providing more effective instruction to a more diverse population of students, the rapid evolution of low-cost online alternatives poses
a serious threat to existing institutions of higher education.
Program/Abstract # 77
Evolutionary origin and functional diversification of retinoid signaling in development
Michael Schubert (Lab Biol Dev de Villefranche sur Mer, France)
Retinoids constitute a group of fat-soluble morphogens related to retinol (vitamin A) that play crucial roles in early development,
organogenesis and tissue homeostasis by regulating cell proliferation, differentiation and apoptosis. In vertebrates, most retinoid
functions are mediated by retinoic acid (RA) binding to heterodimers of the retinoic acid receptor (RAR) and the retinoid X receptor
(RXR). Retinoid signaling was thought to be vertebrate-specific, but studies in invertebrate chordates have revealed RA functions that
are conserved in all chordates. To obtain further insights into the evolutionary diversification of retinoid signaling in the chordate
lineage, we dissected its time-dependent functions during development of two models located at key positions of the chordate tree:
amphioxus (a cephalochordate) and the lamprey (an agnathan vertebrate). Comparison of these species revealed an ancestral role for
retinoid-FGF antagonism in patterning the chordate brain, a mechanism that has been further modified in the gnathostome vertebrate
lineage. Outside chordates, however, evidence for functional roles of retinoid signaling remains scarce, although bioinformatic
analyses indicate that the genes encoding the main mediators of retinoid signaling in chordates are also present in other metazoan
phyla, including xenambulacrarians (e.g. sea urchins, hemichordates) and lophotrochozoans (e.g. annelids, mollusks). These in silico
results suggest that the retinoid pathway has already been present in the last common ancestor of protostomes and deuterostomes.
Altogether, this work thus emphasizes the importance of comparative approaches for understanding the evolution of developmental
mechanisms.
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