Zebrafish prox1b Mutants Develop a Lymphatic Vasculature, and prox1b Does Not Specifically Mark Lymphatic Endothelial Cells

Shijie Tao,Merlijn Witte,Benjamin M Hogan,Robert J Bryson-Richardson,Stefan Schulte-Merker,Peter D Currie,Ferenc Mueller

doi:10.1371/journal.pone.0028934

Abstract

BackgroundThe expression of the Prospero homeodomain transcription factor (Prox1) in a subset of cardinal venous cells specifies the lymphatic lineage in mice. Prox1 is also indispensible for the maintenance of lymphatic cell fate, and is therefore considered a master control gene for lymphangiogenesis in mammals. In zebrafish, there are two prox1 paralogues, the previously described prox1 (also known as prox1a) and the newly identified prox1b.Principal FindingsTo investigate the role of the prox1b gene in zebrafish lymphangiogenesis, we knocked-down prox1b and found that depletion of prox1b mRNA did not cause lymphatic defects. We also generated two different prox1b mutant alleles, and maternal-zygotic homozygous mutant embryos were viable and did not show any lymphatic defects. Furthermore, the expression of prox1b was not restricted to lymphatic vessels during zebrafish development.ConclusionWe conclude that Prox1b activity is not essential for embryonic lymphatic development in zebrafish.

Highlights

In vertebrates, in addition to the blood vasculature, the lymphatic vasculature plays important roles in maintaining an effective circulation
Prox1 is expressed in a variety of tissues other than lymphatic endothelial cells, including the lens, the heart, liver, pancreas, and central nervous system (CNS) [16]
Since zebrafish endothelial cells originate from the lateral plate mesoderm (LPM), we intended to follow prox1b over time

Summary

Introduction

In addition to the blood vasculature, the lymphatic vasculature plays important roles in maintaining an effective circulation. It is responsible for returning the protein-rich interstitial lymph fluid to the blood stream. The lymphatic vessels were first described in 1627 by Aselli [4]. The recent identification of several transcription factors, Prox, Sox, and CoupTF-II [6,7,8], which are essential for the specification of lymphatic cell fate, provides a better understanding of the molecular mechanism of lymphatic development in metazoans. The expression of the Prospero homeodomain transcription factor (Prox1) in a subset of cardinal venous cells specifies the lymphatic lineage in mice. There are two prox paralogues, the previously described prox ( known as prox1a) and the newly identified prox1b

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Conclusion