Untersuchungen zur Bedeutung von Xenopus Islet-1 für die kardiovaskuläre Entwicklung von Xenopus laevis
Auch gedruckt in der BibliothekZ: J-H 11.530 ; W: W-H 9.736
Brade, Thomas Ulrich
FakultätFakultät für Naturwissenschaften
Ressourcen- / MedientypDissertation, Text
Datum der Freischaltung2007-07-27
In this study the spatial and temporal expression pattern of Xisl-1 and its function during cardiovascular development were characterized. Xisl-1 is specifically expressed in heart precursor cells, vascular tissues, cranial placodes and ganglia and in the endoderm. Recently, Isl-1 has been described as a marker gene for the anterior heart field (AHF). It was of interest to demonstrate the existence of the AHF in amphibians. Although it was not possible to directly proof the precedence of the AHF the data give some hints that the Xisl-1+ progenitors indeed constitute this precursor cell line. Xisl-1+ cells were visualized in a very similar anatomical location and generate most likely the same cardiac compartments. The expression of Xisl-1 in cardiac tissues implicates a role for Xisl-1 during normal cardiogeneses in the frog. This issue was analysed using gain and loss of function studies. It was shown that loss of Xisl-1 function leads to a morphological heart phenotype. RT-PCR and whole mount in situ hybridization analyses exhibit the requirement of Xisl-1 function for the expression of cardiac marker genes. Cell proliferation seems not to be regulated by Xisl-1. From this data it was obvious that Xisl-1 is part of the regulatory network which orchestrates normal cardiac development. The gain-of-function experiments showed that Xisl-1 is not sufficient to induce a cardiac cell fate in dorsal or ventral marginal zone explants or whole embryos. On the contrary Xisl-1 mRNA injection leads to an altered formation of the linear heart tube. This phenotype argues for a dose-dependent role of Xisl-1 during cardiac development. Xisl-1 function is additionally required for normal organogenesis of the vascular system. Loss of Xisl-1 function inhibits expression of endothelial marker genes. The data of this study established Xisl-1 as an important regulator of cardiovascular development.
LizenzStandard (Fassung vom 03.05.2003)