Golgi stabilization, not its front-rear bias, is associated with EMT-enhanced fibrillar migration

Abstract

Epithelial-to-mesenchymal transition (EMT) and maturation of collagen fibrils in the tumor microenvironment play a significant role in cancer cell invasion and metastasis. Confinement along fiber-like tracks enhances cell migration. To what extent and in what manner EMT further promotes migration in a microenvironment already conducive to migration is poorly understood. Here, we show that TGF{beta}-mediated EMT significantly enhances migration on fiber-like micropatterned tracks of collagen, doubling migration speed and quadrupling persistence relative to untreated mammary epithelial cells. Thus, cell-intrinsic EMT and extrinsic fibrillar tracks have non-redundant effects on motility. To better understand EMT-enhanced fibrillar migration, we investigated the regulation of Golgi positioning, which is involved in front-rear polarization and persistent cell migration. Confinement along fiber-like tracks has been reported to favor posterior Golgi positioning, whereas anterior positioning is observed during 2d wound healing. While EMT also regulates cell polarity, little is known about its effect on Golgi positioning. Here, we show that EMT induces a 2:1 rearward bias in Golgi positioning; however, positional bias explains less than 5% of single-cell variability in migration speed and persistence. Meanwhile, EMT significantly stabilizes Golgi positioning. Cells that enhance migration in response to TGF{beta} maintain Golgi position for 3-4 fold longer than untreated counterparts, irrespective of whether the Golgi is ahead or behind the nucleus. In fact, 35% of cells that respond to TGF{beta} exhibit a fully-committed Golgi phenotype with the organelle either in the anterior or posterior position for over 90% of the time. Furthermore, single-cell differences in Golgi stability capture up to 30% of variations in migration speed and persistence. These results lead us to propose that the Golgi is part of a core physical scaffold that distributes cell-generated forces necessary for migration. A stable scaffold more consistently, and therefore more productively, distributes forces over time, leading to efficient migration.