Division of Neurogenetics, National Institute of Genetics, Mishima 411-8540, Japan; Department of Genetics, SOKENDAI, Mishima 411-8540, Japan.
Division of Developmental Neurophysiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
Neuron. 2014 Apr 16;82(2):365-79. doi: 10.1016/j.neuron.2014.02.026. Epub 2014 Mar 27.
Thalamocortical (TC) connectivity is reorganized by thalamic inputs during postnatal development; however, the dynamic characteristics of TC reorganization and the underlying mechanisms remain unexplored. We addressed this question using dendritic refinement of layer 4 (L4) stellate neurons in mouse barrel cortex (barrel cells) as a model; dendritic refinement of L4 neurons is a critical component of TC reorganization through which postsynaptic L4 neurons acquire their dendritic orientation toward presynaptic TC axon termini. Simultaneous labeling of TC axons and individual barrel cell dendrites allowed in vivo time-lapse imaging of dendritic refinement in the neonatal cortex. The barrel cells reinforced the dendritic orientation toward TC axons by dynamically moving their branches. In N-methyl-D-aspartate receptor (NMDAR)-deficient barrel cells, this dendritic motility was enhanced, and the orientation bias was not reinforced. Our data suggest that L4 neurons have "fluctuating" dendrites during TC reorganization and that NMDARs cell autonomously regulate these dynamics to establish fine-tuned circuits.
丘脑皮质 (TC) 连接在出生后发育过程中通过丘脑输入进行重组；然而，TC 重组的动态特征和潜在机制仍未被探索。我们使用小鼠桶状皮层 (桶状细胞) 中 L4 星状神经元的树突细化作为模型来解决这个问题；L4 神经元的树突细化是 TC 重组的关键组成部分，通过这种方式，突触后 L4 神经元获得了它们的树突朝向突触前 TC 轴突末端的方向。通过同时标记 TC 轴突和单个桶状细胞树突，我们可以对新生皮层中的树突细化进行活体延时成像。桶状细胞通过动态移动它们的分支来加强树突对 TC 轴突的取向。在 N-甲基-D-天冬氨酸受体 (NMDAR) 缺陷的桶状细胞中，这种树突运动性增强，而取向偏差没有得到加强。我们的数据表明，在 TC 重组过程中，L4 神经元的树突具有“波动”，并且 NMDARs 自主调节这些动力学以建立微调的电路。
