Effects Of Robo2 On Axonal Development Of Nociceptor And Escape Responses In Drosophila

Objective: Robo2 is a member of the Robos family of the immunoglobulin superfamily,which is mainly involved in axon guidance,dendrite branch,nerve repair and cell migration at neuromuscular junction.In this study,we used the nociceptor of Drosophila melanogaster(C4da neurons)as the model to observe the effect of Robo2 on the axonal development of C4 da neurons and stress response of Drosophila melanogaster,to provide experimental basis for further revealing the biological effects of Robo2.Methods: 1.A transgenic Drosophila system suitable for single-cell genetic manipulation was established by hybridization.2.The GAL4/UAS system was employed,and the effects of overexpression and mutation of Robo2 on axonal morphology were observed.3.We did observe the effect of overexpression of Robo2 on the escape behavior of Drosophila larvae.Results: 1.Overexpression of Robo2 on all C4 da neurons resulted in overgrowth of axon terminals of single C4 da neuron,including ddaC,v'ada and vdaB(P<0.01).On the wild-type background,overexpression of Robo2 on only one C4 da neuron resulted in a decrease of axon terminals of single C4 da neurons,that is,overexpression of Robo2 on a single ddaC resulted in a reduction of the length of axon terminals and contralateral branches(P<0.01).2.In the behavioral experiment,compared with the control group,overexpression of Robo2 on all C4 da neurons could shorten the incubation period for ultraviolet stimulation(P<0.001),significantly increase the times of rolling and curling(P<0.001),and quickly escape from the harmful stimulus;while Robo2 mutation could cause the delay of escape response of Drosophila larva to ultraviolet stimulation,reduce the times of rolling(P<0.001).3.Overexpression of Robo2 in all neurons,5-HT neurons and mushroom body(equivalent to mammalian hippocampus)neurons can lead to similar escape behavior changes with C4 da neurons.The overexpression of Robo2 in glial cells can result from the opposite behavior changes of C4 da overexpression of Robo2.The latency of stress is prolonged(P<0.01),and the curling times of larvae is decreased(P<0.05)?4.Overexpression of Robo2 in 5-HT neurons can reduce the length of axon/dendrite trunk(P<0.01),simplify the structure of neurons,and similar phenotypes can be found in overexpression of Robo2 in dopaminergic neurons.5.Overexpression of Robo3 in all C4 da neurons resulted in a decrease in the length of axon terminals,such as ddaC neurons(P<0.001)and v'ada neurons(P<0.001).Conclusion: When all C4 da neurons overexpress Robo2,it can lead to overgrowth of axonal terminals.On the wild-type background,single C4 da neuron overexpresses Robo2 can lead to the reduction of axonal terminal.2.Overexpression of Robo2 in neurons can increase the sensitivity of Drosophila larvae to external stimulation,while overexpression of Robo2 in glial cells can reduce the sensitivity of Drosophila larvae to external stimulus.The regulation of Robo family members on the morphological development of nociceptor in Drosophila is different.