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

Riahi R, Sun J, Wang S, Long M, Zhang DD, Wong PK - Nat Commun (2015)

Bottom Line: However, the factors driving the leader cell formation as well as the mechanisms regulating leader cell density during the migration process remain to be determined.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 signalling to dynamically regulate the density of leader cells during collective cell migration.

View Article: PubMed Central - PubMed

Affiliation: Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, Arizona 85721-0119, USA.

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 the 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 modelling to show that the leader cell identity is dynamically regulated by Dll4 signalling 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 signalling to dynamically regulate the density of leader cells during collective cell migration.

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Related in: MedlinePlus

Dynamics of Dll4 expression and leader cell formation during collective migration(a) Time-lapse fluorescence images characterizing Dll4 mRNA expression. Cells were transfected with dsLNA probes targeting Dll4 mRNA. The model wound was created by scratching the monolayer with a sterilized 1000 μL pipette tip. Scale bars, 50 μm. Representative cells were labeled with numbers (1-7). (b-c) Tracing of Dll4 mRNA expression in representative cells in a illustrating the dynamic behaviors and competitive characteristics of leader cells in collective migration (n = 3). Pixel intensity data are expressed as the mean ± s.e.m.
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Figure 2: Dynamics of Dll4 expression and leader cell formation during collective migration(a) Time-lapse fluorescence images characterizing Dll4 mRNA expression. Cells were transfected with dsLNA probes targeting Dll4 mRNA. The model wound was created by scratching the monolayer with a sterilized 1000 μL pipette tip. Scale bars, 50 μm. Representative cells were labeled with numbers (1-7). (b-c) Tracing of Dll4 mRNA expression in representative cells in a illustrating the dynamic behaviors and competitive characteristics of leader cells in collective migration (n = 3). Pixel intensity data are expressed as the mean ± s.e.m.

Mentions: The dsLNA probe for Dll4 mRNA allowed us to track the initiation and evolution of leader cells. The Dll4 expression of leader cells was monitored near the boundary using time-lapse microscopy (Supplementary Movie 1). The formation of leader cells was highly dynamic. Leader cells with upregulated Dll4 mRNA and motile phenotypes were detected approximately 4 hours after wounding. Dll4 upregulation was primarily observed near the boundary (Fig. 2a). The majority of leader cells were initiated from the first row (> 80%), although they occasionally originated from the second row (n = 30 and Supplementary Fig. 3a). Tracking the Dll4 expression revealed the diverse behavior of cells. While some cells near the leading edge increased Dll4 expression after wounding, other cells decreased or maintained their level of Dll4 (Fig. 2b). The latter behaved as followers during migration. Interestingly, a portion (~10%) of cells transiently increased Dll4 expression, with the expression decreasing eventually to basal level (Fig. 2c and Supplementary Fig 3b). These results indicate leader cell formation is triggered and regulated dynamically after the creation of the cell-free region.


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

Riahi R, Sun J, Wang S, Long M, Zhang DD, Wong PK - Nat Commun (2015)

Dynamics of Dll4 expression and leader cell formation during collective migration(a) Time-lapse fluorescence images characterizing Dll4 mRNA expression. Cells were transfected with dsLNA probes targeting Dll4 mRNA. The model wound was created by scratching the monolayer with a sterilized 1000 μL pipette tip. Scale bars, 50 μm. Representative cells were labeled with numbers (1-7). (b-c) Tracing of Dll4 mRNA expression in representative cells in a illustrating the dynamic behaviors and competitive characteristics of leader cells in collective migration (n = 3). Pixel intensity data are expressed as the mean ± s.e.m.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4380165&req=5

Figure 2: Dynamics of Dll4 expression and leader cell formation during collective migration(a) Time-lapse fluorescence images characterizing Dll4 mRNA expression. Cells were transfected with dsLNA probes targeting Dll4 mRNA. The model wound was created by scratching the monolayer with a sterilized 1000 μL pipette tip. Scale bars, 50 μm. Representative cells were labeled with numbers (1-7). (b-c) Tracing of Dll4 mRNA expression in representative cells in a illustrating the dynamic behaviors and competitive characteristics of leader cells in collective migration (n = 3). Pixel intensity data are expressed as the mean ± s.e.m.
Mentions: The dsLNA probe for Dll4 mRNA allowed us to track the initiation and evolution of leader cells. The Dll4 expression of leader cells was monitored near the boundary using time-lapse microscopy (Supplementary Movie 1). The formation of leader cells was highly dynamic. Leader cells with upregulated Dll4 mRNA and motile phenotypes were detected approximately 4 hours after wounding. Dll4 upregulation was primarily observed near the boundary (Fig. 2a). The majority of leader cells were initiated from the first row (> 80%), although they occasionally originated from the second row (n = 30 and Supplementary Fig. 3a). Tracking the Dll4 expression revealed the diverse behavior of cells. While some cells near the leading edge increased Dll4 expression after wounding, other cells decreased or maintained their level of Dll4 (Fig. 2b). The latter behaved as followers during migration. Interestingly, a portion (~10%) of cells transiently increased Dll4 expression, with the expression decreasing eventually to basal level (Fig. 2c and Supplementary Fig 3b). These results indicate leader cell formation is triggered and regulated dynamically after the creation of the cell-free region.

Bottom Line: However, the factors driving the leader cell formation as well as the mechanisms regulating leader cell density during the migration process remain to be determined.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 signalling to dynamically regulate the density of leader cells during collective cell migration.

View Article: PubMed Central - PubMed

Affiliation: Department of Aerospace and Mechanical Engineering, The University of Arizona, Tucson, Arizona 85721-0119, USA.

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 the 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 modelling to show that the leader cell identity is dynamically regulated by Dll4 signalling 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 signalling to dynamically regulate the density of leader cells during collective cell migration.

Show MeSH
Related in: MedlinePlus