| The neural circuit processes and integrates all kinds of information obtained by peripheral nerve system to avoid danger or to survive.The brain is comprised of modules,which contains lots of layers and columns as repeated smaller units or local neural circuits.A set of columns involved in similar stimulations or movements is arranged into one module,which preserves the high-fidelity transmission and intergration of information to central nerve system.So far,however,the underlying molecular mechanism of column restriction and proper synaptic connection in a narrow and tight space is still not clear.Neurexins are an important cell adhesion molecule,which bind to Neuroligins involved in synaptogenesis and synapse transmission.In our research,we take the visual system of Drosophila as model and utilize genetics,molecular biology and biochemistry,cell biology,and developmental biology to elucidate the molecular mechanism of Drosophila homolog of ?-Neurexin(DNrx)restricting a L4 axonal terminal in one column.First,we find that loss of DNrx in L4 neurons results in L4 axonal terminals projecting into neighborhood columns.Then,we identify that DNrx binds to Ephrin by its C-terminal and deleption of DNrx leads to decreased expression and diffused distribution of Ephrin.Furthermore,we find that knock-down of Ephrin in L4 neurons are enough to cause defective column restriction of L4 axons.We conduct experiment studies of cell and verified that DNrx promotes Ephrin clustering on the membrane by binding with Ephrin,which mediates column restriction of L4 axonal terminals.At last,we illustrate that knock-down of Drosophila Neuroligin 4(DNlg4)in Tm2 neurons,downstream of L4 neurons,lead to L4 axonal terminals projecting into neighborhood columns.Our research reveales that Eph/Ephrin signaling functions in column restriction and the processes of axon guidance and synaptogenesis are consecutive and associated.We also propose a novel function of Neurexin in axon guidance. |
PDF Full Text Request