Notch1-Dll4 signalling and mechanical force regulate leader cell formation during collective cell migration.

Reza Riahi,Shue Wang,Donna D Zhang,Jian Sun,Pak Kin Wong,Min Long

doi:10.1038/ncomms7556

Abstract

At the onset of collective cell migration, a subset of cells within an initially homogenous population acquires a distinct “leader” phenotype with characteristic morphology and motility. However, the factors driving leader cell formation as well as the mechanisms regulating leader cell density during the migration process remain to be determined. Here, we use single cell gene expression analysis and computational modeling to show that leader cell identity is dynamically regulated by Dll4 signaling through both Notch1 and cellular stress in a migrating epithelium. Time-lapse microscopy reveals that Dll4 is induced in leader cells after the creation of the cell-free region and leader cells are regulated via Notch1-Dll4 lateral inhibition. Furthermore, mechanical stress inhibits Dll4 expression and leader cell formation in the monolayer. Collectively, our findings suggest that a reduction of mechanical force near the boundary promotes Notch1-Dll4 signaling to dynamically regulate the density of leader cells during collective cell migration.

Highlights

At the onset of collective cell migration, a subset of cells within an initially homogenous population acquires a distinct ‘leader’ phenotype with characteristic morphology and motility
Integrins a3 and a5 along with myosin light-chain activity in fibroblasts are required for force-mediated matrix remodelling; these factors are not required in the trailing carcinomas, suggesting biomechanical coupling and a leader–follower organization in the invasion process
We studied the expression of Dll[4], which is expressed in endothelial cells during angiogenesis[22,23]

Summary

Introduction

At the onset of collective cell migration, a subset of cells within an initially homogenous population acquires a distinct ‘leader’ phenotype with characteristic morphology and motility. We use single-cell gene expression analysis and computational modelling to show that the leader cell identity is dynamically regulated by Dll[4] signalling through both Notch[1] and cellular stress in a migrating epithelium. Our findings suggest that a reduction of mechanical force near the boundary promotes Notch1–Dll[4] signalling to dynamically regulate the density of leader cells during collective cell migration. Exchanging leaders in the invading front was observed in breast cancer cells in collagen gel[21] It is not known how leader cells are initiated among the initially homogeneous population, nor is it known how leader cell density is dynamically regulated during collective migration. We investigate the initiation, regulation and function of leader cells during collective cell migration using single-cell gene expression analysis in conjunction with computational modelling. Using a combined experimental and computational approach, the interplays of Notch1–Dll[4] signalling and intercellular force in the emergence of leader cells are investigated

Methods

Results

Conclusion