Origin and development of striated muscles in the tail of axolotl embryos

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Mechanisms of axis (neural tube, notochord, epidermis, somites) formation in the vertebrate tail di-verge from those in the trunk. Thus, studying tail formation can provide insight into the flexibility of different developmental programs. For example, striated tail muscle is not recruited from trunk somites but from neural plate and neural fold of the posterior neurula. It is unknown on a molecular level whether these tissues originally specified to become neural divert to mesodermal fates later or represent pluripotent stem cells. Using the axolotl (Ambystoma mexicanum) as experimental model this proposal focuses mainly on identifying the mesodermal versus neuronal character of the posterior neural plate and posterior neural fold/neural crest (NC) tissues by ectopic tissue grafting and by in situ hybridization. Furthermore, the detailed and separate contribution of posterior neural plate and neural fold/NC to striated tail muscle will be investigated by grafting tissue fragments from transgenic (GFP+ and Cherry+) axolotl donors into white hosts and by studying their distribution in the host tail. The NC origin of striated tail muscles will be investigated via transgenic animals. Another important objective of the proposal are the cell and tissue interactions leading to tail formation. They will be analyzed on a single cell level with immunohistochemistry and molecular biology. Our expertise and the newly developed labelling methods will provide progress within the neglected field of vertebrate tail formation as a model for neural versus mesodermal induction.