[Establishment of an in vitro model system for the differentiation of synaptically coupled neurons from mouse...

The investigation of fundamental differentiation processes and toxic effects during the neurogenesis in the embryo is still difficult, since there are only a few suitable cellular model systems available so far. The isolation of neurons from early embryonic origin results in a very small amount of cells and a high number of laboratory animals is required for this purpose. Permanent tumor cell lines, able to differentiate into neuron-like cell types, are only a limited alternative for the use of primary cultures. None of the known permanent cell lines is capable to form terminally differentiated, synaptically coupled neurons in vitro. Embryonic stem (ES) cells can generate cell types of all 3 germ layers and provide a new possibility to study developmental processes on a cellular level. Nevertheless the successful differentiation of neurons from ES cells has not been shown. By using the ES cell line BLC 6 and cultivation of the cells in embryo-like aggregates (embryoid bodies), we were able to differentiate efficiently neuronal cells in vitro. The electrophysiological characterization of the BLC 6-derived neurons shows that these cells carry the complex electrical properties of postmitotic neurons and are coupled by inhibitory and excitatory synapses. The BLC 6 model probably represents the only developmental cell model suitable for studies from pluripotent stem cells to terminal differentiated neurons.