| Popis: |
Several key features about the nematode, C. elegans, make it a tractable model system for the analysis of behavior. C. elegans allows genetic analysis of behavior in an animal with few neurons and few connections between these neurons. Male mating behavior in C. elegans requires the coordination of several steps: response to contact with the hermaphrodite; turning around her head or tail; location of the vulva; insertion of the spicules into the vulva; and sperm transfer. I have chosen to study this relatively complex behavior in this simple system to begin to understand how complex behaviors are coordinated. I have taken two approaches to the problem that take advantage of the unique characteristics of C. elegans. First, since all cells are reproducibly identifiable in this system, I lesioned individual structures and neurons to determine which neurons mediate mating behavior. By cell ablation, we have identified participating sensory neurons for each step of mating behavior. The sensory rays mediate response and turning. The neurons of the hook and post-cloacal sensillae mediate vulva location. Two pairs of the spicule neurons mediate spicule insertion, while another pair regulates sperm transfer. In addition, some inter and motor neurons have been identified which participate in these steps. Second, I screened for mutants impaired in mating behavior. From the screen, we have isolated mutants defective in each step of the behavior. These results independently suggest that the different steps of mating behavior are independently mutable and therefore likely mediated by separable neuronal system. In addition, mutants were isolated that appear to have hermaphrodite specific defects, indicating along with ablation results that a hermaphrodite signal is required for the initiation of sperm transfer. In conclusion, I have found that the steps in mating behavior are to a large extent separable. Male mating behavior in C. elegans is not entirely innately controlled, but rather the initiation of each step and the integration between steps is highly regulated by sensory feedback. |
