The Francis Crick Institute, Visual Circuit Assembly Laboratory, 1 Midland Road, London, NW1 1AT, UK.
Nat Commun. 2018 Jun 12;9(1):2295. doi: 10.1038/s41467-018-04592-z.
Visual motion detection in sighted animals is essential to guide behavioral actions ensuring their survival. In Drosophila, motion direction is first detected by T4/T5 neurons. Their axons innervate one of the four lobula plate layers. How T4/T5 neurons with layer-specific representation of motion-direction preferences are specified during development is unknown. We show that diffusible Wingless (Wg) between adjacent neuroepithelia induces its own expression to form secondary signaling centers. These activate Decapentaplegic (Dpp) signaling in adjacent lateral tertiary neuroepithelial domains dedicated to producing layer 3/4-specific T4/T5 neurons. T4/T5 neurons derived from the core domain devoid of Dpp signaling adopt the default layer 1/2 fate. Dpp signaling induces the expression of the T-box transcription factor Optomotor-blind (Omb), serving as a relay to postmitotic neurons. Omb-mediated repression of Dachshund transforms layer 1/2- into layer 3/4-specific neurons. Hence, spatio-temporal relay mechanisms, bridging the distances between neuroepithelial domains and their postmitotic progeny, implement T4/T5 neuron-subtype identity.
在有视力的动物中，视觉运动检测对于指导行为动作以确保其生存至关重要。在果蝇中，T4/T5 神经元首先检测到运动方向。它们的轴突支配四个小叶板层中的一个。在发育过程中，如何特异性地指定具有特定运动方向偏好的 T4/T5 神经元尚不清楚。我们发现，相邻神经上皮之间的可扩散 Wingless (Wg) 诱导其自身表达形成次级信号中心。这些中心激活专门产生第 3/4 层特异性 T4/T5 神经元的相邻侧三级神经上皮区域中的 Decapentaplegic (Dpp) 信号。源自缺乏 Dpp 信号核心域的 T4/T5 神经元采用默认的第 1/2 层命运。Dpp 信号诱导 T 盒转录因子 Optomotor-blind (Omb) 的表达，作为向有丝分裂后神经元的中继。Omb 介导的 Dachshund 抑制将第 1/2 层转化为第 3/4 层特异性神经元。因此，时空中继机制在神经上皮区域与其有丝分裂后后代之间架起桥梁，实现 T4/T5 神经元亚型身份。
