The role of vasculature and blood circulation in zebrafish swimbladder development

Cecilia Lanny Winata,Zhiyuan Gong,Vladimir Korzh,Igor Kondrychyn,Svetlana Korzh

doi:10.1186/1471-213x-10-3

Abstract

BackgroundRecently we have performed a detailed analysis of early development of zebrafish swimbladder, a homologous organ of tetrapod lung; however, the events of swimbladder development are still poorly characterized. Many studies have implicated the role of vascular system in development of many organs in vertebrates. As the swimbladder is lined with an intricate network of blood capillaries, it is of interest to investigate the role of the vascular system during early development of swimbladder.ResultsTo investigate the role of endothelial cells (ECs) and blood circulation during development of the swimbladder, phenotypes of swimbladder were analysed at three different stages (~2, 3 and 5 dpf [day postfertilization]) in cloche (clo) mutant and Tnnt2 morphants, in the background of transgenic lines Et(krt4:EGFP)sq33-2 and Et(krt4:EGFP)sqet3 which express EGFP in the swimbladder epithelium and outer mesothelium respectively. Analyses of the three tissue layers of the swimbladder were performed using molecular markers hb9, fgf10a, acta2, and anxa5 to distinguish epithelium, mesenchyme, and outer mesothelium. We showed that the budding stage was independent of ECs and blood flow, while early epithelial growth, mesenchymal organization and its differentiation into smooth muscle, as well as outer mesothelial organization, were dependent on ECs. Blood circulation contributed to later stage of epithelial growth, smooth muscle differentiation, and organization of the outer mesothelium. Inflation of the swimbladder was also affected as a result of absence of ECs and blood flow.ConclusionOur data demonstrated that the vascular system, though not essential in swimbladder budding, plays an important role in the development of the swimbladder starting from the early growth stage, including mesenchyme organization and smooth muscle differentiation, and outer mesothelial organization, which in turn may be essential for the function of the swimbladder as reflected in its eventual inflation.

Highlights

We have performed a detailed analysis of early development of zebrafish swimbladder, a homologous organ of tetrapod lung; the events of swimbladder development are still poorly characterized
Swimbladder vascular system In order to characterize the vascular anatomy of the swimbladder in vivo, as well as to observe the dynamics of blood circulation in the developing swimbladder, we performed two genetic crosses between transgenic lines; Et(krt4:EGFP)sq33-2 and Tg(fli1:EGFP)y1, were crossed to show blood vessels formation around swimbladder and Et(krt4:EGFP)sq33-2 was crossed with Tg(gata1:dsRed)sd2 for observation of erythrocytes circulating in the vessels and to identify the initiation of circulation
We have demonstrated that the lack of endothelial cells (ECs) or blood circulation has no effect on swimbladder development during budding stage, but affects its growth in early growth phase by the lack of ECs and in late growth phase by the lack of blood circulation

Summary

Introduction

We have performed a detailed analysis of early development of zebrafish swimbladder, a homologous organ of tetrapod lung; the events of swimbladder development are still poorly characterized. It is difficult to study this structure in most vertebrate models in vivo due to the opacity of the embryo as well as the in utero development in mammals. In this respect, the zebrafish model has two major advantages. The development of the zebrafish swimbladder has been described recently and its developmental events have been shown to be similar to that of early mammalian lung development [9]. The end result is a structure consisting of a pneumatic duct and a swimbladder main chamber which is inflated at 5 dpf

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Discussion

Conclusion