PDF(Pubmed)
Abstract：
A primary cilium is a membrane-bound extension from the cell surface that contains receptors for perceiving and transmitting signals that modulate cell state and activity. Primary cilia in the brain are less accessible than cilia on cultured cells or epithelial tissues because in the brain they protrude into a deep, dense network of glial and neuronal processes. Here, we investigated cilia frequency, internal structure, shape, and position in large, high-resolution transmission electron microscopy volumes of mouse primary visual cortex. Cilia extended from the cell bodies of nearly all excitatory and inhibitory neurons, astrocytes, and oligodendrocyte precursor cells (OPCs) but were absent from oligodendrocytes and microglia. Ultrastructural comparisons revealed that the base of the cilium and the microtubule organization differed between neurons and glia. Investigating cilia-proximal features revealed that many cilia were directly adjacent to synapses, suggesting that cilia are poised to encounter locally released signaling molecules. Our analysis indicated that synapse proximity is likely due to random encounters in the neuropil, with no evidence that cilia modulate synapse activity as would be expected in tetrapartite synapses. The observed cell class differences in proximity to synapses were largely due to differences in external cilia length. Many key structural features that differed between neuronal and glial cilia influenced both cilium placement and shape and, thus, exposure to processes and synapses outside the cilium. Together, the ultrastructure both within and around neuronal and glial cilia suggest differences in cilia formation and function across cell types in the brain.
摘要：
初级纤毛是来自细胞表面的膜结合延伸,其含有用于感知和传递调节细胞状态和活性的信号的受体。大脑中的初级纤毛比培养细胞或上皮组织上的纤毛更难以接近，因为它们在大脑中突出到深处，神经胶质和神经元过程的密集网络。这里,我们调查了纤毛频率,内部结构,形状,和大的位置，小鼠初级视觉皮层的高分辨率透射电子显微镜体积。纤毛从几乎所有兴奋性和抑制性神经元的细胞体中延伸出来，星形胶质细胞,和少突胶质细胞前体细胞（OPCs），但少突胶质细胞和小胶质细胞不存在。超微结构比较显示，神经元和神经胶质之间的纤毛和微管组织的基部不同。调查纤毛近端特征显示，许多纤毛与突触直接相邻，表明纤毛准备遇到局部释放的信号分子。我们的分析表明，突触接近可能是由于神经纤维中的随机相遇，没有证据表明纤毛会调节突触活动，正如在四部门突触中所预期的那样。在突触附近观察到的细胞类别差异很大程度上是由于外部纤毛长度的差异。神经元和神经胶质纤毛之间的许多关键结构特征不同，影响纤毛的位置和形状，因此，暴露于纤毛外的过程和突触。一起,神经元和神经胶质纤毛内部和周围的超微结构表明，大脑中不同细胞类型的纤毛形成和功能存在差异。
