Investigating the mechanisms of cardiac patterning and morphogenesis using a heart formation assay

Using Xenopus laevis embryos, the aim of this project is to establish a new experimental model to help understand the mechanism that regulates cardiac cell diversification and heart morphogenesis. In order to achieve these goals we use two assays. The cardiogenesis assay involves the use of animal cap explants excised from the animal pole of blastua embryos. Here it is shown that GATA-4 reliably induces the expression of ventricular and proepicardial markers, providing an assay to study the mechanisms of cardiac cell fate diversification. However, cardiomyocytes generated in animal pole explants do not undergo significant morphogenesis and physiological maturation. In order to study these later aspects of heart development we required a different assay to generate a structure similar to the heart. Using GATA-4 injected AC explants transplanted into host embryos we obtained secondary beating hearts in which regionally restricted cardiac gene expression was observed in addition to growth and a limited degree of morphogenesis. We demonstrated that the host plays an essential role as it provides a wide range of permissive regions which allow the development of the SH. Moreover, we also showed that the competence to generate a secondary heart is lost in reaggregates transplanted at stage 28. The host cells however do not contribute to the SH indicating that the role of the host is providing signals which allow the development of the SH.EThOS - Electronic Theses Online ServiceGBUnited Kingdo