Abstract Book Cover - Weinstein 2012 - University of Chicago

S4.6 Nephronectin regulates axial vein morphogenesis in zebrafish
Chinmoy Patra* 1 , Filomena Ricciardi 1 , Iva Nikolic 2 , Mirko HH Schmidt 2 , Benno Jungblut 1 , Felix B. Engel 1
Max-Planck-Institute for Heart and Lung Research
Angiogenesis is the development of new vessels from pre-existing vessels. This is a critical morphological event
both in organ development as well as in diseases. Like in other vertebrates, in zebrafish vessels form a complex
network in order to fulfill tissue oxygen demands. Development of complex vascular networks is dependent on
the directional migration of groups of endothelial cells, which is called angiogenic sprouting. Here we have
demonstrated that in zebrafish the extracellular matrix protein, nephronectin, is transiently expressed in the
caudal vein plexus forming region at the time of caudal vein sprouting at around 30 hours post fertilization (hpf).
Morpholino-mediated nephronectin depletion resulted in the malformation of the caudal vein plexus and the
ventral vein and in the frequent loss of inter-segmental veins. Time-lapse analysis from 28 hpf to 40 hpf
indicated a decreased in the frequency of caudal vein sprout formation in nephronectin morphants. In addition,
existing sprouting appeared multi-directional indicating a navigation problem. Biochemical analysis
demonstrated that nephronectin is able to bind to the integrin αV/β3 heterodimer. Importantly, integrin αV and
nephronectin expression overlapped in the region of the caudal vein plexus. Moreover, morpholino-mediated
integrin αV knockdown in zebrafish phenocopied nephronectin depletion. Taken together, our data indicate that
nephronectin regulates directional sprouting of the axial vein in zebrafish, which might be via integrin αV.
4.7 Coordinated patterning mechanisms of blood vessels and peripheral nerves
Mukouyama Y.
Stem Cell and Neuro-Vascular Biology, GDBC, NHLBI, NIH
Anatomical proximity and close patterning of nerves and blood vessels suggest that there is interdependence
between the two networks. The first such indication of this interplay is the responsiveness of vascular
development to signals secreted by peripheral sensory nerves in the developing skin. We suggests a
coordinated mechanism in which nerve derived-signals is responsible for vascular patterning signal to recruit
vessels to align with nerves, and for arterial differentiation in the nerve-associated vessels. Interestingly, we
discovered a reciprocal guidance event in the patterning of peripheral sympathetic nerves in the developing
heart. Our whole-mount imaging approaches revealed that the pattern of large-diameter coronary veins
influences the pattern of sympathetic innervation in the developing heart. Further genetic studies and in vitro
organ culture experiments demonstrated that coronary veins serve as an intermediate template that guides
distal sympathetic axon projection via local signal by coronary vascular smooth muscle cells. Our results
suggest that target organs possess unique and stereotypical patterns of innervation, mediated by tissue substructures,
such as coronary veins in the heart, that are adapted to complex organ structure and physiology.
4.8 Targeted non-invasive occlusion of pharyngeal arch arteries during avian cardiac morphogenesis
Stephanie Lindsey, Huseyin C. Yalcin, Akshay Shekhar, Nozomi Nishimura, Chris B. Schaffer, Jonathan T.
Butcher
Department of Biomedical Engineering, Cornell University
The role of hemodynamics in outflow tract and pharyngeal arch artery morphogenesis is poorly understood.
Through the use of two- photon microscopy guided femtosecond laser pulses, we nucleated and controlled the
growth of microbubbles within outflow vessels without disturbing surrounding tissues. These bubbles
temporarily occluded the vessel, during which time a stable occlusion could be formed by ablating the circulating
thrombocytes that accumulated behind the bubble. These clot-like structures then persisted. Using this
approach, we examine the effects of PAA vessel occlusions on embryonic viability, hemodynamic
rearrangement, and downstream outflow tract morphogenesis. We determine that occlusion of the right IV
pharyngeal arch artery caused lethality in 99.5% of embryos by day 6 (HH28/29), while occlusion of the left IV
arch artery was significantly less lethal. In each case, blood flow was redistributed to the III and VI PAA and
vessel diameters were altered significantly. With right IV PAA occlusion, the right III PAA artery increased 47%
in diameter while the right VI decreased 100%. Interestingly, ultrasound derived blood velocity did not change in
the right III PAA but significantly increased in the right VI. No changes in diameter or velocity were seen in the
contralateral PAA. When both IV PAA were occluded, both PAA vessels changed in diameter, resulting in an
overall decrease in ouflow lumen area. These results support that PAA hemodynamics are important
contributor to embryonic development.
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