INGEBI   02650
INSTITUTO DE INVESTIGACIONES EN INGENIERIA GENETICA Y BIOLOGIA MOLECULAR "DR. HECTOR N TORRES"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
ELECTRICAL ACTIVITY REGULATES PLEXIN A3-MEDIATED AXON PATHFINDING IN DEVELOPING ZEBRAFISH SPINAL MOTOR NEURONS.
Autor/es:
P.V. PLAZAS; NICHOLAS C. SPITZER
Lugar:
Cancun
Reunión:
Congreso; 1st Meeting of the Federation of Latin American and Caribbean Societies for Neurosciences; 2012
Resumen:
One of the puzzles in neurosciences is how neuronal circuits are formed during the development of the nervous system. While the role of genetic programs in this process is well understood, evidence for a role of electrical activity is quite limited.In zebrafish embryos, each spinal hemisegment contains 3 primary motorneurons (PMN), named CaP, MiP and RoP, and ~30 secondary motorneurons (SMN). We simultaneously characterized PMN axon outgrowth and Ca2+ activity during pathfinding behavior in transgenic Hb9:Gal4/UAS:GCaMP3 embryos. Between 17 hr (PMN axonogenesis) and 24 hr post fertilization, PMN display two types of spontaneous Ca2+ transients: waves and spikes. Ca2+ waves are generated in both PMN and SMN, with similar durations and frequencies. In contrast, only PMN exhibit specific patterns of Ca2+ spiking activity at different developmental stages. Suppression of Ca2+ spiking activity by stochastic expression of inward rectifier K+ channels (hKir) in single PMN led to errors in MiP and RoP axon pathfinding. Errors comprise aberrant branching in 30% of MiPs and intraspinal pathfinding mistakes in 26% of RoPs. Misguided RoP axons either extend towards the endogenous exit point but bypass it or orient away from it. Axon trajectories of hKir-expressing PMN were restored to normal when the activity of nearby cells was also suppressed; suggesting that an activity-based competition rule is a key regulator of PMN axon pathfinding.The guidance receptor PlexinA3 plays a major role in PMN axon pathfinding. Coinjections of PlexinA3 morpholino (MO) with hKir cDNA induced a synergistic effect in the incidence of pathfinding errors compared with embryos injected either with PlexinA3 MO alone or hKir cDNA alone. Moreover, whole mount in situ hybridizations showed that PlexinA3 expression is not regulated by activity.Our results provide an in vivo demonstration of the role of spontaneous electrical activity in axon pathfinding, modulating PlexinA3 signal transduction pathway.