Hiesinger P R, Reiter C, Schau H, Fischbach K F
University of Freiburg, Institute of Biology III, D-79104 Freiburg, Germany.
J Neurosci. 1999 Sep 1;19(17):7548-56. doi: 10.1523/JNEUROSCI.19-17-07548.1999.
To investigate a possible involvement of synaptic machinery in Drosophila visual system development, we studied the effects of a loss of function of neuronal synaptobrevin, a protein required for synaptic vesicle release. Expression of tetanus toxin light chain (which cleaves neuronal synaptobrevin) and genetic mosaics were used to analyze neuropil pattern formation and levels of selected neural adhesion molecules in the optic lobe. We show that targeted toxin expression in the developing optic lobe results in disturbances of the columnar organization of visual neuropils and of photoreceptor terminal morphology. IrreC-rst immunoreactivity in neuropils is increased after widespread expression of toxin. In photoreceptors, targeted toxin expression results in increased Fasciclin II and chaoptin but not IrreC-rst immunoreactivity. Axonal pathfinding and programmed cell death are not affected. In genetic mosaics, patches of photoreceptors that lack neuronal synaptobrevin exhibit the same phenotypes observed after photoreceptor-specific toxin expression. Our results demonstrate the requirement of neuronal synaptobrevin for regulation of cell adhesion molecules and development of the fine structure of the optic lobe. A possible causal link to fine-tuning processes that may include synaptic plasticity in the development of the Drosophila CNS is discussed.
为了研究突触机制在果蝇视觉系统发育中可能的作用，我们研究了神经元突触小泡蛋白功能丧失的影响，该蛋白是突触小泡释放所必需的。利用破伤风毒素轻链（可切割神经元突触小泡蛋白）的表达和基因嵌合体来分析视叶中神经毡模式的形成以及所选神经粘附分子的水平。我们发现，在发育中的视叶中靶向毒素表达会导致视觉神经毡的柱状组织和光感受器末端形态出现紊乱。毒素广泛表达后，神经毡中的IrreC-rst免疫反应性增强。在光感受器中，靶向毒素表达会导致Fasciclin II和chaoptin免疫反应性增加，但不会导致IrreC-rst免疫反应性增加。轴突导向和程序性细胞死亡不受影响。在基因嵌合体中，缺乏神经元突触小泡蛋白的光感受器斑块表现出与光感受器特异性毒素表达后观察到的相同表型。我们的结果证明了神经元突触小泡蛋白对于调节细胞粘附分子和视叶精细结构发育的必要性。本文还讨论了与微调过程可能存在的因果联系，这些过程可能包括果蝇中枢神经系统发育中的突触可塑性。
