Molecular mechanisms regulating subventricular zone progenitor migration

我们的神经细胞绝大多数是在胎儿发育过程中产生的。然而，大脑的两个区域包含干细胞，并在一生中不断产生数十万个新的神经细胞。二十多年来，我的实验室一直在积极研究这些干细胞和它们制造的神经细胞。其中一个区域是室管膜下区(SEZ)，负责制造长距离迁移的神经细胞。它们从经济特区转移到一个名为嗅球的大脑区域，该区域与嗅觉有关。当我们通过实验抑制迁移时，新生的神经细胞死亡和嗅觉减弱.围绕经济特区神经细胞迁移还有许多悬而未决的问题。答案是至关重要的，因为正确的迁移是大脑功能的基础。当迁移出错时，胚胎可能会出现大脑畸形，并导致精神发育迟缓和癫痫等神经问题。迁移是一个动态的过程，最好地实时可视化和理解；我们开发了一种强大的双光子延时显微镜，它可以检测组织深处的神经细胞迁移，而不会损坏它。我们的显微镜使用脉冲速度令人难以置信的激光来生成荧光标记细胞的三维图像，然后我们将其重建成电影。使用先进的软件，我们跟踪细胞的位置，从而产生丰富和详细的细胞运动信息。我们最近发现，一种名为Galectin-3(Gal-3)的蛋白质专门调节SEZ神经细胞的迁移。我们的新发现令人着迷，因为已知Gal-3影响癌症和炎症，但不影响正常的大脑过程。虽然Gal-3在脑损伤中是已知的，但我们的工作证明它在健康的大脑中也有效。事实上，Gal-3只在经济特区被发现，而不是在其他大脑区域。GAL-3多任务频发：除了迁移外，还能调节细胞分裂和存活。我们发现Gal-3的这种影响不会发生在经济特区；它只对迁徙很重要。虽然我们展示了Gal-3调节迁移，但它具体是如何做到这一点还不清楚。在这个项目中，我们试图发现Gal-3调节神经细胞运动的方式。1)检测其对SEZ细胞黏附的促进作用。我们相信Gal-3可以与其他蛋白质相互作用，以维持细胞间的适当水平的黏附。太多的黏附会导致细胞被粘住而不能移动；太少的黏附会导致细胞无法获得运动所需的牵引力。我们还将测试Gal-3介导的黏附在多大程度上导致从单个细胞迁移到群体迁移的转变。2)我们将测试Gal-3是否调节运动纤毛以及这些路线图的建立。GAL-3在SEZ细胞上表达，具有可移动的纤毛，小的鞭状突起导致脑液(脑脊液)流动。流体流动产生分子梯度，形成神经细胞向正确方向迁移的路线图。3)接下来，我们将测试Gal-3是否通过与另一种名为表皮生长因子受体(EGFR)的蛋白质相互作用来调节迁移。我们发现EGFR在SEZ神经细胞迁移中起重要作用，并且受Gal-3调控。4)最后，我们将测试Gal-3‘S表亲Gal-1是否与其相互作用来调节神经细胞迁移。最后一个实验很重要，因为Gal-1调控SEZ的增殖，但其在迁移中的功能仍未得到测试。通过定义神经细胞迁移的分子调控，该项目将填补对成年神经细胞产生整个过程的理解的一大空白。细胞迁移是胚胎发育的一般特征，也与成人免疫系统的正常功能和癌症相关。因此，从这些研究中收集到的见解预计将具有多种兴趣，并适用于研究中的生物学家和实践中的临床医生。

The large majority of our nerve cells are generated during fetal development. However, two regions of the brain contain stem cells and continuously make hundreds of thousands of new nerve cells throughout life. My laboratory has actively studied these stem cells and the nerve cells they make for over twenty years. One of the regions, the subependymal zone (SEZ), makes nerve cells that migrate long distances. They move from the SEZ to a brain region called the olfactory bulb which has to do with the sense of smell. When we experimentally inhibit the migration, the newborn nerve cells whither and die and olfaction diminshes. There are many unsolved questions surrounding SEZ nerve cell migration. The answers are vital to discover as proper migration is fundamental for brain function. When migration goes wrong, brain malformations can arise in the embryo and lead to neurological problems such as mental retardation and epilepsy. Migration is a dynamic process best visualized and understood in real-time; we developed a powerful 2-photon time-lapse microscope that detects nerve cell migration deep in tissue without damaging it. Our microscope employs lasers that pulse incredibly rapidly to generate three-dimensional images of fluorescently labeled cells, which we then reconstruct into movies. Using advanced software, we track cell positions and thus generate rich and detailed information on cell movement. We recently discovered that a protein called galectin-3 (Gal-3) specifically regulates SEZ nerve cell migration. Our novel finding was fascinating because Gal-3 was known to affect cancer and inflammation but not normal brain processes. Although Gal-3 was known in brain injury, our work proved that it also works in the healthy brain. In fact, Gal-3 was found only in the SEZ, and no other brain region. Gal-3 frequently "multi-tasks": in addition to migration, it can also regulate cell division and survival. We found such effects of Gal-3 do not occur in the SEZ; it was only important for migration. Although we showed Gal-3 regulates migration, the specific way in which it does so is unclear. In this project we seek to discover the ways Gal-3 regulates nerve cell movement. 1) We will test how much it promotes adhesion of SEZ cells. We believe Gal-3 interacts with other proteins to maintain the right level of adhesion between cells. Too much adhesion causes cells to get stuck and not move; too little adhesion and they will not have the traction needed for motility. We will also test how much Gal-3 mediated adhesion causes shifts from individual cell migration to group migration. 2) We will test whether Gal-3 regulates motile cilia and the establishment of these road maps. Gal-3 was expressed on SEZ cells with motile cilia, small whip-like protrusions that cause brain fluid (cerebrospinal fluid) flow. The fluid flow creates molecular gradients, which form a road map for nerve cells to migrate in the right direction. 3) We will next test if Gal-3 regulates migration by interacting with another protein called epidermal growth factor receptor (EGFr). We showed EGFr is important for SEZ nerve cell migration and that it is controlled by Gal-3. 4) Finally, we will test if Gal-3's cousin, Gal-1, interacts with it to regulate nerve cell migration. This last experiment is important since Gal-1 regulates SEZ proliferation but its function in migration remains untested.By defining the molecular regulation of nerve cell migration, this project will fill a big gap in the understanding of the overall process of adult nerve cell production. Cell migration is a general feature of embryonic development and is also relevant for the adult immune system's normal function and in cancer. Therefore the insights gleaned from these studies are predicted to be of multiple interest and applicable to biologists in research and clinicians in practice.