Genes - Circuits - Behavior, Max Planck Institute of Neurobiology, 82152 Martinsried near Munich, Germany; email:
Annu Rev Cell Dev Biol. 2013;29:385-416. doi: 10.1146/annurev-cellbio-101011-155748.
Synaptic connections between neurons form the basis for perception and behavior. Synapses are often clustered in space, forming stereotyped layers. In the retina and optic tectum, multiple such synaptic laminae are stacked on top of each other, giving rise to stratified neuropil regions in which each layer combines synapses responsive to a particular sensory feature. Recently, several cellular and molecular mechanisms that underlie the development of multilaminar arrays of synapses have been discovered. These mechanisms include neurite guidance and cell-cell recognition. Molecules of the Slit, Semaphorin, Netrin, and Hedgehog families, binding to their matching receptors, bring axons and dendrites into spatial register. These guidance cues may diffuse over short distances or bind to sheets of extracellular matrix, thus conditioning the local extracellular milieu, or are presented on the surface of cells bordering the future neuropil. In addition, mutual recognition of axons and dendrites through adhesion molecules with immunoglobulin domains ensures cell type-specific connections within a given layer. Thus, an elaborate genetic program assembles the parallel processing channels that underlie visual perception.
神经元之间的突触连接构成了感知和行为的基础。突触通常在空间中聚集，形成刻板的层状结构。在视网膜和视顶盖中，多个这样的突触层相互堆叠，形成分层的神经胶质区域，其中每一层结合对特定感觉特征有反应的突触。最近，发现了几种支持多层突触排列发育的细胞和分子机制。这些机制包括神经突导向和细胞-细胞识别。Slit、Semaphorin、Netrin 和 Hedgehog 家族的分子与它们匹配的受体结合，将轴突和树突带入空间登记。这些导向线索可以在短距离内扩散，或者结合到细胞外基质的薄片上，从而调节局部细胞外环境，或者呈现在未来神经胶质边界的细胞表面。此外，通过具有免疫球蛋白结构域的粘附分子进行轴突和树突的相互识别，确保了特定层内的细胞类型特异性连接。因此，一个精心设计的遗传程序组装了构成视觉感知基础的并行处理通道。
