Molecular mechanisms regulating subventricular zone progenitor migration

我们的大部分神经细胞是在胎儿发育过程中产生的。然而，大脑的两个区域含有干细胞，并在一生中不断产生数十万个新的神经细胞。我的实验室已经积极研究这些干细胞和它们产生的神经细胞超过20年了。其中一个区域，室管膜下区（SEZ），使神经细胞长距离迁移。他们从经济特区转移到大脑中一个叫做嗅球的区域，这个区域与嗅觉有关。当我们实验性地抑制迁移时，新生的神经细胞会死亡，嗅觉也会减弱。有许多未解决的问题，围绕经济特区神经细胞迁移。答案是至关重要的，因为正确的迁移是大脑功能的基础。当迁移出现问题时，胚胎中可能会出现大脑畸形，并导致精神发育迟滞和癫痫等神经问题。迁移是一个动态的过程，最好是实时可视化和理解;我们开发了一种功能强大的双光子延时显微镜，可以检测组织深处的神经细胞迁移，而不会对其造成损伤。我们的显微镜采用激光，脉冲非常快，可以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，从而生成丰富而详细的细胞运动信息。我们最近发现，一种称为半乳糖凝集素-3（Gal-3）的蛋白质特异性地调节SEZ神经细胞迁移。我们的新发现很吸引人，因为Gal-3已知会影响癌症和炎症，但不会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也在健康的大脑中起作用。事实上，Gal-3只在经济特区被发现，而没有其他大脑区域。Gal-3经常“多任务”：除了迁移，它还可以调节细胞分裂和存活。我们发现Gal-3的这种作用在经济特区不会发生;它只对迁移很重要。虽然我们表明Gal-3调节迁移，但其具体方式尚不清楚。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)我们将测试它在多大程度上促进SEZ细胞的粘附。我们认为Gal-3与其他蛋白质相互作用，以维持细胞之间正确的粘附水平。太多的粘附导致细胞被卡住而不能移动;太少的粘附，它们将没有运动所需的牵引力。我们还将测试多少Gal-3介导的粘附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是否调节运动纤毛和这些路线图的建立。Gal-3在具有活动纤毛的SEZ细胞上表达，所述活动纤毛是引起脑液（脑脊液）流动的小鞭状突起。液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)我们接下来将测试Gal-3是否通过与另一种称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对于SEZ神经细胞迁移是重要的，并且它由Gal-3控制。4)最后，我们将测试Gal-3的表亲Gal-1是否与它相互作用以调节神经细胞迁移。最后一个实验很重要，因为Gal-1调节SEZ增殖，但其在迁移中的功能尚未得到验证。通过定义神经细胞迁移的分子调节，该项目将填补对成体神经细胞产生的整个过程的理解的巨大空白。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有关。因此，从这些研究中收集到的见解预计将具有多重利益，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.