Congress Abstracts - Society for Developmental Biology

development is already unknown. Embryos of 8.5-18.5 days post coitum (dpc) were obtained from pregnant mice -CD1 strain- 2
postnatal days (dpn) mice were also evaluated; atrium and ventricles were dissected and studied separately. Reverse transcriptase PCR
was performed to analyze the expression of mRNA of AR, Nppa and Myh6; beta actin was used as endogenous control. The presence
of the protein was evaluated by immunohistochemistry. Results: The mRNA and the protein of AR were expressed from 12.5 dpc to 2
dpn mice. The AR mRNA is differentially expressed in atrium and ventricles at 16.5 dpc, 18.5 dpc and 2 dpn mice with the highest
expression in atrial tissue. The expression of mRNA of Nppa and Myh6 displayed a similar pattern with prevalence in atria. These
results indicate that androgen receptor could have a role in the functional differentiation of cardiomyocytes. Also, the differential
expression between atria and ventricle suggest that androgen receptor could be involved in the physiology and development of atria.
Partly supported by PAPIIT IN226811
Program/Abstract # 371
Withdrawn
Program/Abstract # 372
A heterogeneous cellular origin of the cardiac lymphatic vasculature.
Klotz, Linda; Ruhrberg, Christiana (University College London, UK); Riley, Paul (University of Oxford, UK)
The lymphatic vasculature is a blind-ended network crucial for tissue fluid homeostasis, immune surveillance and lipid adsorption
from the gut, as well as being the main route of cancer metastasis. The heart is the first organ to develop in mammals, however little is
known about the lymphatic vasculature in the heart. The mechanisms regulating the development of the cardiac lymphatic vessels, as
well as their cellular origin, are yet to be described. In this study we shed light on the development and origin of the cardiac lymphatic
vasculature from mid-gestation to early adulthood in mice. We show that lymphatic vessels first sprout at embryonic day 14.5 (E14.5)
in the outflow region of the heart and develop alongside coronary blood vessels, completing development and largely encompassing
the heart by postnatal day 15 (P15). We have utilized various Cre transgenic mouse lines to give a comprehensive overview of lineage
contributions to the cardiac lymphatic vessels. Contrary to the current dogma of the field suggesting that veins give rise to the entire
lymphatic network, our lineage tracing analyses suggest a heterogeneous cellular origin for developmental de novo
lymphvasculogenesis in the heart – with the involvement of both blood endothelial as well as other lineages. O ur characterization of
the cardiac lymphatic vasculature offers novel insight into a largely overlooked, but arguably very important part of the lymphatic
system. Future studies will focus on applying the findings from lymphatic development in the embryonic heart to adult cardiovascular
pathology and disease.
Program/Abstract # 373
Elucidation of the molecular mechanism of Rasip1 and Arhgap29 in blood vessel development.
Koo, Yeon (Univ of Texas Southwestern Med Ctr, USA), Xu, Ke (Harvard, USA); Davis, George (Univ. of Missouri, United States);
Cleaver, Ondine (Univ of Texas Southwestern Med Ctr, USA)
Cardiovascular function depends on patent, continuous blood vessel formation by endothelial cells (ECs). Blood vessel development
initiates during ‘vasculogenesis’ via the aggregation of ECs into linear aggregates, which then form tubes with a central lumen that
allows blood flow. However the mechanisms underlying vascular ‘tubulogenesis’ are only beginning to be unraveled. We recently
showed that a novel GTPase-interacting protein called Rasip1 and its binding partner the RhoGAP Arhgap29 are required for
formation of continuous blood vessel lumens. Rasip1 null embryos showed disrupted localization of EC polarity and junctional
complexes, and loss of adhesion of ECs to extracellular matrix (ECM). In vitro studies also showed that depletion of either Rasip1 or
Arhgap29 in cultured ECs lead to failed tubulogenesis and abrogation of integrin-dependent adhesion contact maturation. From these
studies, we propose that Rasip1 and Arhgap29 regulate multiple cellular processes required for functional vascular tubulogenesis.
Program/Abstract # 374
Annexin A3 is required for early blood vessel formation
Meadows, Stryder M.; Fletcher, Peter (UT Southwestern Medical Center, USA); Sacharidou, Anastasia; Davis, George (University of
Missouri, USA); Cleaver, Ondine (UT Southwestern Medical Center, USA)
Annexins are a unique class of proteins that bind to membrane phospholipids in a calcium-dependent manner. They are able to
function in several different capacities that include organizing membrane domains and cytoskeletal linkages, as well as regulating both
exocytic and endocytic transport and the flow of ions across cell membranes. While annexins are linked to many cellular processes,
the function of Annexin A3 (Anxa3) during development is completely unknown. Our studies show that Anxa3 expression is
conserved in the endothelial cell (EC) lineage of mice, frogs and fish, suggesting an important role during vascular development.
Morpholino (MO) studies demonstrate an essential requirement for Anxa3 during early blood vessel formation, as Anxa3 MO-treated
Xenopus embryos lack the tight junction molecule Claudin-5 and exhibit severe disruptions in EC-EC adhesion and failure of vascular
cord formation. Furthermore, Anxa3 siRNA-treated ECs fail to assemble into vessel-like networks in 3D collagen matrices in vitro,
suggesting adhesion defects. Overall, these studies demonstrate a requirement for Anxa3 in assembly and coalescence of ECs, and are
the first to indicate a role for Anxa3 during vascular development.
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