Meeting Abstract
62.2 Thursday, Jan. 6 Iterative connections reveal functional segments in Caenorhabditis elegans locomotion network HASPEL, G*; O’DONOVAN, MJ; NINDS; NINDS haspelg@ninds.nih.gov
75 motorneurons of 8 classes innervate the body musculature that propels C. elegans. These motorneurons receive input mostly from 5 pairs of interneurons and are synaptically interconnected to create a motorneuronal network. To date, only the anterior half of the motorneuronal network of one animal, spanning 42 motorneurons, has been reconstructed from TEM micrographs to provide a connectivity data set that is unavailable for any other animal model. We have analyzed this data set by mapping each motorneuron in perimotor space (with respect to the muscle fibers it innervates along the body). We expressed all the connections made by each motorneuron according to their relative position to other motorneurons of the same class. We filtered out connections that occurred only once in the data set and described a typical connectivity pattern for each class. We found that connections in the data set are significantly more iterated compared to computer-generated networks in which the targets of connections were shuffled. Most connections made by each motorneuron iterate within its class. We describe a repeating segment that contains 11 motorneurons and Iterated it six times along the body of a nematode to give a connectivity model. We are using this connectivity model of the motorneuronal network to give context to the recorded activity of motorneurons during locomotion. We expressed a calcium sensor in subsets of motorneurons to record their activity and correlate i to locomotion behavior. We found that some classes of motorneurons are dedicated to either forward or backward locomotion, forming two overlapping motorneuronal networks. A neuronal network comprised of direction-specific classes of motorneurons, might be an ancestral form of locomotor control to which dedicated and multifunctional interneurons were subsequently added.
