The Development And Function Of AMsh And CEPsh Glia

Glial cells are important components of the nervous system. They are intensively contributed to the development and function of neurons. However, the current research data were mostly gained from cultured cells and brain slices, but not in vivo study. Therefore, It remains largely unknown how glial cells response to physiological stimuli in vivo,and how this response effects neuronal function, sensory and behavioral generation. In addition, the molecular mechanisms of glial cell’s growth and neurite orientation are also not clear.In this study, based on Caenorhabditis elegans (C.elegans),we used combined approaches of molecular genetics, optogenetics, in vivo electrophysiology, in vivo calcium imaging and behavioral analysis, addressed the following questions:1) How AMsh glial cells response physical and chemical stimuli and its underlying molecular mechanisms;2) A forward genetic screening for key factors involved in CEPsh glial development and neurite orientation.We found that both mechanical and chemical stimuli can induce AMsh glial calcium transients. IAA-induced calcium increases show two phases:a fast calcium transient and a sustained phase. Compared to olfactory and gustatory neurons, the calcium signaling from AMsh glia is slower and much more sustained, indicating that AMsh glia may be involved in sensory modulation (such as adaptive and neural plasticity) and other tuned physiological process. IP3R/itr-1and L-type VDCC/egl-19are required for IAA-induced calcium signaling from AMsh glia. The calcium elevation is reduced in neurotransmitters and neuropeptides defect mutants.Using in-vivo whole cell patch-clamp recording, we recorded touch-induced currents from AMsh glia. Though extracellular Amiloride can block touch-receptor currents from touch receptor neuron ASH, touch-induced currents from AMsh are not affected by this drug. The currents do not depend on MEC-4, DEG-1and TRP-4, the three identified mechanosensitive ion channels and do not affected in neurontransmitters and neuropeptides defct mutants. These observations suggest AMsh glia is likely a new class of mechanical receptor cell, which directly respond to mechanical stimuli.We applyed optogenetic method to specifically activate CEPsh glial cells in free-moving C.elegans, and found a significant increase in the frequency of backward locomotion, suggesting that glia activation may affect the neural circuits and behavior.We got some mutant strains with defects in the development of CEPsh glia and/or CEP neuron by EMS genetic screening. Using SNP mapping and gene sequencing, we found a mutant strain zuml is cused by a point mutant in vab-3gene, which orthologous gene PAX6was previously found be involved in the development of oligodendrocytes.This study successively established an experimental platform for the in vivo study of neuron-glia interaction. It will better define the roles of C.elegans glial cells in sensory generation and behaviors. It also provides a fantastic opportunity to indentify the core molecular mechanism of neuron-glia interaction in higher organisms and has the potenial to provide new insights into possible diagnostic tools and treatments for chronic pain, epilepsy, depression and other neuropsychiatric disorders.