Study On The Mechanism Of Axonal Pathway Of Dorsal Terminal Neurons In Early Development Of Zebrafish Embryonic

The telencephalon represents the most highly evolved region in the vertebrate brain, and play crucial roles in sensing the outside world. However, little has been known about the telencephalon neuron subtypes and the axon pathfinding. This project has mainly focused on the molecular mechanisms underlying neuron axonal pathfinding within the zebrafish dorsal telencephalon. We first studied zebrafish anterior dorsal telencephalic (ADt) neuron development. Using single cell labeling, ISH and other technologies, we found that the ADt axonal projection patterns were heterogeneous. Then we determined roundabout2(Robo2) and deleted in colorectal cancer (Dcc) were differentially expressed in the ADt neurons. We found knocking down Robo2function by injecting antisense morpholino oligonucleotides abolished the ipsilateral SOT originating from the ADt neurons. Knocking down Dcc did not prevent formation of the AC and the SOT. In contrast, the AC was specifically reduced when Netrinl function was knocked down. Further mechanistic studies suggested that Robo2responded to the repellent Slit signals and suppressed the attractive Netrin signals. In order to examine whether wnt play roles in regulating ADt neuron pathfinding process, we treat embryos with an activator of the wnt signaling pathway:BIO (a GSK3β inhibitor). To avoid gross malformation due to altered patterning during gastrulation, we started ectopic of Wnt signaling at18.5hpf and treated embryos up to36hpf. In BIO treated embyos, the ADt origin SOT were significantly affacted or reduced, and real-time PCR result showed that the expression of Robo2was supressed. We treated Robo2mRNA injected embryos with BIO from18.5hpf to36hpf, the SOT restored. In conclusion, our findings demonstrate how Robo2-Slit, Dec-Netrin and wnt coordinate the axonal projection choices of the developing neurons in the vertebrate forebrain.