果蝇Neuroligin 4以非依赖于Neurexin方式调控突触的发育

Neuroligin 4 is independent of neurexin in regulating synaptic development in Drosophila

目的探究果蝇突触黏附分子神经连接蛋白-4(Drosophila neuroligin 4,DNlg4)对幼虫神经肌肉突触发育的调控是否依赖于经典的neuroligin(Nlg)突触前配体分子轴突蛋白(Drosophila neurexin,DNrx)。方法主要利用免疫荧光染色和激光共聚焦显微观测技术,对包括野生型、dnlg4突变体、dnrx突变体和dnlg4,dnrx双突变体等不同基因型果蝇三龄幼虫的神经肌肉接头(neuromuscular junction,NMJ)的形态进行观察,测量其突触分枝总长度并计数突触终扣(bouton)数目。以此作为NMJ发育状态参数,通过比较不同基因型果蝇的NMJ发育缺陷程度,确定DNlg4和DNrx在调控神经肌肉突触发育中的关系。结果DNrx缺失会导致较DNlg4缺失更严重的NMJ发育缺陷;缺失DNlg4会进一步加重因DNrx缺失而导致的NMJ发育缺陷;运动神经元表达外源的DNlg4可部分挽救DNrx缺失造成的NMJ发育缺陷;未检测到两类分子存在在体的相互结合。结论DNlg4与DNrx对果蝇幼虫神经肌肉突触发育的正向调控具有协同效应,DNlg4以非依赖于DNrx的方式调控神经肌肉突触的发育。

Objective To determine if the Drosophila synaptic adhesion molecule neuroligin 4(DNlg4)regulates the development of the larval neuromuscular synapse by interacting with the classic neuroligin(Nlg)-presynaptic ligand molecule Drosophila neurexin(DNrx).Methods Immunofluorescence staining and confocal microscopy were used to examine the morphology of the neuromuscular junction(NMJ)in Thrid-instar larvae in wild-type(WT),dnlg4 mutant,dnrx mutant,and dnlg4,dnrx double-mutant Drosophila.The length of the synaptic branches and number of synaptic boutons were used as parameters to assess the developmental status of the NMJ in the different genotypes.We determined the relationship between DNlg4 and DNrx in regulating the development of the NMJ by comparing the developmental defects in the different genotypes.Results Deletion of DNrx result ed in more severe developmental defects in NMJs than DNlg4 deletion,characterized by shorter synaptic branches and fewer boutons.Loss of DNlg4 further aggravated the NMJ defects caused by DNrx deletion.The expression of exogenous DNlg4 in motoneurons partially rescued the developmental defects of NMJs caused by loss of DNrx.No in vivo physical interaction between DNlg4 and DNrx was detected.Conclusions DNlg4 and DNrx have synergistic effects on the positive regulation of synaptic development in Drosophila larvae,and DNlg4 regulates synaptic development in a DNrx-independent manner.