Department of Biological Structure, University of Washington, Seattle, Washington 98195, USA.
J Neurosci. 2012 Jul 25;32(30):10306-17. doi: 10.1523/JNEUROSCI.1581-12.2012.
Sensory circuits use common strategies, such as convergence and divergence, typically at different synapses, to pool or distribute inputs. Inputs from different presynaptic cell types converge onto a common postsynaptic cell, acting together to shape neuronal output (Klausberger and Somogyi, 2008). Also, individual presynaptic cells contact several postsynaptic cell types, generating divergence of signals. Attaining such complex wiring patterns relies on the orchestration of many events across development, including axonal and dendritic growth and synapse formation and elimination (reviewed by Waites et al., 2005; Sanes and Yamagata, 2009). Recent work has focused on how distinct presynaptic cell types form stereotypic connections with an individual postsynaptic cell (Morgan et al., 2011; Williams et al., 2011), but how a single presynaptic cell type diverges to form distinct wiring patterns with multiple postsynaptic cell types during development remains unexplored. Here we take advantage of the compactness of the visual system's first synapse to observe development of such a circuit in mouse retina. By imaging three types of postsynaptic bipolar cells and their common photoreceptor targets across development, we found that distinct bipolar cell types engage in disparate dendritic growth behaviors, exhibit targeted or exploratory approaches to contact photoreceptors, and adhere differently to the synaptotropic model of establishing synaptic territories. Furthermore each type establishes its final connectivity patterns with the same afferents on separate time scales. We propose that such differences in strategy and timeline could facilitate the division of common inputs among multiple postsynaptic cell types to create parallel circuits with diverse function.
感觉回路使用共同的策略，如汇聚和发散，通常在不同的突触处，将输入汇集或分配。来自不同突触前细胞类型的输入汇聚到共同的突触后细胞上，共同作用以塑造神经元输出（Klausberger 和 Somogyi，2008）。此外，单个突触前细胞接触几种突触后细胞类型，产生信号发散。实现这种复杂的布线模式依赖于许多事件在发育过程中的协调，包括轴突和树突生长以及突触形成和消除（Waites 等人，2005 年；Sanes 和 Yamagata，2009 年）。最近的工作集中在不同的突触前细胞类型如何与单个突触后细胞形成定型连接（Morgan 等人，2011 年；Williams 等人，2011 年），但在发育过程中，单个突触前细胞类型如何发散形成与多个突触后细胞类型的不同连接模式仍未得到探索。在这里，我们利用视觉系统第一个突触的紧凑性来观察老鼠视网膜中这种回路的发育情况。通过对三种类型的突触后双极细胞及其共同的光感受器靶标进行成像，我们发现不同的双极细胞类型表现出不同的树突生长行为，表现出有针对性或探索性的接触光感受器的方式，并以不同的方式依附于建立突触领地的突触趋同模型。此外，每种类型都以不同的时间尺度与相同的传入神经建立其最终的连接模式。我们提出，这种策略和时间线上的差异可以促进共同输入在多个突触后细胞类型之间的分配，从而形成具有不同功能的并行回路。
