Xenopus locomotor interneuron lineage tracing and functional interrogation using lights. (360G-Wellcome-089319_Z_09_Z)

Major advances have been made in understanding the neuronal control of locomotion in lower vertebrates, mainly by making electrical recordings from individual, or sometimes pairs of neurons and by studying the synaptic connections they make. Such work enables inferences to be drawn about likely events that occur in the different populations of neurons that control locomotion. We wish to use a new approach to test some of these inferences. The approach exploits the use of light-sensitive, and li gand-sensitive, ion-channels and ion pumps to control neuronal activity. Expression of the appropriate exogenous proteins in an identified population of neurones makes possible their selective activation or inhibition. Early embryonic blastomeres of Xenopus laevis are uniquely predisposed to develop into specific types of neuron in the tadpole spinal cord. Thus, injection of the required cRNAs into appropriate blastomeres results in the labelling of specified classes of neurons whose activity ca n then be controlled by light, or a selectively-acting ligand (see pilot work). Our major objective is to evaluate the roles of different interneurons more precisely during swimming activity in the spinal cord and caudal hindbrain of the Xenopus tadpole.