Background

Cell migration plays a key role in many physiological (morphogenesis, tissue repair, regeneration) and pathological (tumor metastasis, atherosclerosis) processes. It is a highly orchestrated multistep process, which requires dynamic interactions between cells and the extracellular cues such as chemokines and signals from the extracellular matrix. In response to the extracellular cues, cells acquire a polarized morphology. Cell polarization requires delicate regulation of microtubule and actin polymerization for asymmetrical distribution of signaling molecules, cytoskeletal proteins, and directional vesicle trafficking. At the leading edge, actin polymerization drives the extension of membrane protrusions, such as lamellipodia (facilitating focal adhesion formation to anchor the protrusion) and filopodia (sensing the environment). In order to move forward, cells have to disassemble adhesions on the trailing edge and retract the trailing end, which require coordination of microtubule and actin networks (Palazzo and Gundersen, 2002; Wehrle-Haller and Imhof, 2003; Etienne-Manneville, 2004). Disruption of cell migration and polarization would affect the process of neurogenesis, and may lead to neurodevelopmental disorders or brain tumor progression (Rakic, 2003; Götz and Huttner, 2005; Taylor et al., 2005; Wang et al., 2016).

Neural and glial progenitor cells are the major proliferating and migrating cells in the CNS, and are crucial for the development of neurological functions of an organism. Neural and glial progenitor cells have also been implicated as the cell origin of gliomas. Indeed, glioma migration and infiltration recapitulate key aspects of glial progenitor cell migration during development. Specifically, glioma cells, similar to glial progenitors in the developing CNS, bear a unipolar or a bipolar morphology with a leading process and migrate along white matter tracts and blood vessels (Cayre et al., 2009).

In this report, we will introduce a live-cell migration assay and the analytical methods which allow us to study cell motility in the presence of inhibitors or different environmental cues. We will first demonstrate how to isolate and culture neural and glial progenitor cells. Next, we will demonstrate our approach to capturing time-lapse images, and to tracking migrating cells for quantification. The live-cell migration assay can be applied to neural and glial progenitor cells as well as to tumor spheres. This assay can also be used to study cell motility in response to inhibitors, different extracellular substrates and stiffness, attractive or repulsive cues, as well as changes in the electrical field (Li et al., 2015) without optimizing the duration of migration and final detection.