The Role Of Myosin X In Neuron Axon Elongation And Pathfinding

Myosin X (Myo X), an actin-based motor protein, was discovered in inner ear by PCR in 1994. Myosin X, a vertebrate-specific member of myosin super-family, can be detected in most tissues and cells, such as kidney, liver, brain, and so on. An interesting thing is that in addition to full-length Myo X, brain expresses a shorter form of Myo X. The role of Myo X in development of neural system is not clear yet. Full-length Myo X can stimulate the formation or stabilization of filopodia. When full-length Myo X is over-expressed, it increases the number and length of filopodia in COS-7 cells, while the over-expression of the tail of Myo X leads the decrease and disappearance of filopodia. Therefore, headless Myo X can be used to investigate the role of myosin X in the development of neuronal system. Recently the literature showed that Myo X could interact with DCC and neogenin which were receptors of netrin-1. However, the role of Myo X in axonal guidance continues to be investigated. In this research, a serial of constructed of Myo X expressional vectors were trasfected into NG108-15 cells, the number and length of cell filopodia were increased when Myo X-Fl and Myo X-head protein were over-expressed, while the cells transfected with pEGFP-MyoX-tail were round and had few filopodia. In addition, Myo X localized at the edge of lampodia or the tip of filopodia. In neuron the Myo X and DCC nearly co-localized and a large number of branches were found in axon after induced by Netrin-1. Thereafter, a serial of constructed of Myo X vectors and pFlag-DCC/pFlag-neogenin were co-transfected into HEK 293T cells, and then investigated the interaction between Myo X and DCC/ neogenin by co-immunoprecipitation using protein G. The positive result of the interaction between Myo X-tail protein and DCC was obtained. A system of explant culture was established and the role of Myo X in neuronal migration was studied finally. After culturing in 50 hours, many single neurons migrated out from the explant. The cell migration was inhabited when 2ug/ml myo X antibody was added,. In conclusion, over-expression of Myo X revealed that the head domain of Myo X was important for elongation of axon.Co-localization and interaction between Myo X and DCC suggested that Myo X was an essential member in neural axon guidance pathway induced by Netrin-1-DCC. Also, Myo X may be an important factor in neuron migration.