The model organism C. elegans Part II: Neurobiology 王歐力 教授 Oliver I. Wagner, PhD Professor National Tsing Hua University Institute of Molecular & Cellular Biology Department of Life Science C. elegans neurobiology • Anatomy of C. elegans nervous system • Structure and function of sensory neurons • Mechanosensing • Chemotaxis and thermotaxis • Male sensory neurons and mating behavior • Motor circuits • Synapses, NMJs and neurotransmitter • Electrophysiological methods • Habituation and learning C. elegans neurobiology • The C. elegans nervous system is simple and well described • It consists of 302 neurons interconnected by chemical and electrical (gap junctions) synapses • The position and the characteristic of each neuron does not vary from animal to animal which makes it a very good model organism for studying neuronal processes • Even though the neuronal system is simple, it regulates a wide variety of behaviors: • different mechanosensory responses (light, harsh, nose and texture touch) • chemosensory responses (e.g., can differentiate various types of alcohols) • thermotaxis (can detect < 0.1ºC) • complex responses to food with habituation and learning • locomotion (complex moving behavior) • egg-laying and defecation • complex male mating behavior Compared to Drosophila, there are more neuronal protein coding genes in C. elegans Total 145 251 Littleton and Ganetzky, 2000, Neuron Basic features of the nervous system nerve ring neuronal marker (UNC-104::GFP) expressed in C. elegans Basic features of the nervous system Neurons are paired head vulva tail vulva head tail Basic features of the nervous system Neurons are paired P = posterior A = anterior L = lateral M = microtubule cell N = interneuron R/L = right/left Basic features of the nervous system: Neuron bundles sublaterals sublaterals Dorsal nerve cord Ventral nerve cord Nerve ring (not shown) Basic features of the nervous system: Commissures • Some ventrally located motor neurons make commissures to the dorsal nerve cord • Interestingly, most commissures are located on the right side of the worm Commissures Basic features of the nervous system