title: Muscle contraction phenotypic analysis enabled by optogenetics reveals functional relationships of sarcomere components in Caenorhabditis elegans.
abstract: The sarcomere, the fundamental unit of muscle contraction, is a highly-ordered complex of hundreds of proteins. Despite decades of genetics work, the functional relationships and the roles of those sarcomeric proteins in animal behaviors remain unclear. In this paper, we demonstrate that optogenetic activation of the motor neurons that induce muscle contraction can facilitate quantitative studies of muscle kinetics in C. elegans. To increase the throughput of the study, we trapped multiple worms in parallel in a microfluidic device and illuminated for photoactivation of channelrhodopsin-2 to induce contractions in body wall muscles. Using image processing, the change in body size was quantified over time. A total of five parameters including rate constants for contraction and relaxation were extracted from the optogenetic assay as descriptors of sarcomere functions. To potentially relate the genes encoding the sarcomeric proteins functionally, a hierarchical clustering analysis was conducted on the basis of those parameters. Because it assesses physiological output different from conventional assays, this method provides a complement to the phenotypic analysis of C. elegans muscle mutants currently performed in many labs; the clusters may provide new insights and drive new hypotheses for functional relationships among the many sarcomere components.
authors.affiliation: School of Chemical &Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
authors.forename: Hyundoo
authors.initials: H
authors.lastname: Hwang
authors.affiliation: Department of Pathology, Emory University, Atlanta, GA, USA.
authors.forename: Dawn E
authors.initials: DE
authors.lastname: Barnes
authors.affiliation: Department of Pathology, Emory University, Atlanta, GA, USA.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Matsunaga
authors.affiliation: Department of Pathology, Emory University, Atlanta, GA, USA.
authors.forename: Guy M
authors.initials: GM
authors.lastname: Benian
authors.affiliation: Department of Pathology, Emory University, Atlanta, GA, USA.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Ono
authors.affiliation: School of Chemical &Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA.|Interdisciplinary Program of Bioengineering, Georgia Institute of Technology, Atlanta, GA, USA.|The Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA.
authors.forename: Hang
authors.initials: H
authors.lastname: Lu
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology*; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D009119:Muscle Contraction; D009154:Mutation; D062308:Optogenetics; D010641:Phenotype; D012518:Sarcomeres / Q000502:physiology*
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