Stork Tobias, Engelen Daniel, Krudewig Alice, Silies Marion, Bainton Roland J, Klämbt Christian
Institut für Neurobiologie, Universität Münster, D-48149 Münster Germany.
J Neurosci. 2008 Jan 16;28(3):587-97. doi: 10.1523/JNEUROSCI.4367-07.2008.
The function of a complex nervous system depends on an intricate interplay between neuronal and glial cell types. One of the many functions of glial cells is to provide an efficient insulation of the nervous system and thereby allowing a fine tuned homeostasis of ions and other small molecules. Here, we present a detailed cellular analysis of the glial cell complement constituting the blood-brain barrier in Drosophila. Using electron microscopic analysis and single cell-labeling experiments, we characterize different glial cell layers at the surface of the nervous system, the perineurial glial layer, the subperineurial glial layer, the wrapping glial cell layer, and a thick layer of extracellular matrix, the neural lamella. To test the functional roles of these sheaths we performed a series of dye penetration experiments in the nervous systems of wild-type and mutant embryos. Comparing the kinetics of uptake of different sized fluorescently labeled dyes in different mutants allowed to conclude that most of the barrier function is mediated by the septate junctions formed by the subperineurial cells, whereas the perineurial glial cell layer and the neural lamella contribute to barrier selectivity against much larger particles (i.e., the size of proteins). We further compare the requirements of different septate junction components for the integrity of the blood-brain barrier and provide evidence that two of the six Claudin-like proteins found in Drosophila are needed for normal blood-brain barrier function.
复杂神经系统的功能取决于神经元和神经胶质细胞类型之间复杂的相互作用。神经胶质细胞的众多功能之一是为神经系统提供有效的绝缘，从而实现离子和其他小分子的精细稳态。在此，我们对构成果蝇血脑屏障的神经胶质细胞组成进行了详细的细胞分析。通过电子显微镜分析和单细胞标记实验，我们对神经系统表面的不同神经胶质细胞层进行了表征，即神经周胶质层、神经周下胶质层、包裹性胶质细胞层以及一层厚厚的细胞外基质——神经板。为了测试这些鞘的功能作用，我们在野生型和突变体胚胎的神经系统中进行了一系列染料渗透实验。比较不同突变体中不同大小荧光标记染料的摄取动力学可以得出结论，大部分屏障功能由神经周下细胞形成的紧密连接介导，而神经周胶质细胞层和神经板则有助于对更大颗粒（即蛋白质大小）的屏障选择性。我们进一步比较了不同紧密连接成分对血脑屏障完整性的要求，并提供证据表明果蝇中发现的六种Claudin样蛋白中的两种是正常血脑屏障功能所必需的。
