[
WormBook,
2010]
The nervous system represents the most complex tissue of C. elegans both in terms of numbers (302 neurons and 56 glial cells = 37% of the somatic cells in a hermaphrodite) and diversity (118 morphologically distinct neuron classes). The lineage and morphology of each neuron type has been described in detail and neuronal fate markers exists for virtually all neurons in the form of fluorescent reporter genes. The ability to "phenotype" neurons at high resolution combined with the amenability of C. elegans to genetic mutant analysis make the C. elegans nervous system a prime model system to elucidate the nature of the gene regulatory programs that build a nervous system-a central question of developmental neurobiology. Discussing a number of regulatory genes involved in neuronal lineage determination and neuronal differentiation, I will try to carve out in this review a few general principles of neuronal development in C. elegans. These principles may be conserved across phylogeny.
[
WormBook,
2005]
Synaptogenesis is a process involving the formation of a neurotransmitter release site in the presynaptic neuron and a receptive field at the postsynaptic partners, and the precise alignment of pre- and post-synaptic specializations. In C. elegans synapses are found as en passant axonal swellings along the nerve processes. Genetic screens using a synaptic vesicle-associated GFP marker have identified key players in synaptic target recognition and organization of the presynaptic terminals. Importantly, the functions of most genes are evolutionarily conserved. Further studies using a combination of genetic modifier screens and reverse genetics have begun to reveal the underlying signaling pathways.
[
Genetics,
2021]
The model research animal Caenorhabditis elegans has unique properties making it particularly advantageous for studies of the nervous system. The nervous system is composed of a stereotyped complement of neurons connected in a consistent manner. Here, we describe methods for studying nervous system structure and function. The transparency of the animal makes it possible to visualize and identify neurons in living animals with fluorescent probes. These methods have been recently enhanced for the efficient use of neuron-specific reporter genes. Because of its simple structure, for a number of years, C. elegans has been at the forefront of connectomic studies defining synaptic connectivity by electron microscopy. This field is burgeoning with new, more powerful techniques, and recommended up-to-date methods are here described that encourage the possibility of new work in C. elegans. Fluorescent probes for single synapses and synaptic connections have allowed verification of the EM reconstructions and for experimental approaches to synapse formation. Advances in microscopy and in fluorescent reporters sensitive to Ca2+ levels have opened the way to observing activity within single neurons across the entire nervous system.