Spatial mapping of directionality and speed of WT and Krt6a/Krt6b-null keratinocytes migrating on type I collagen by PIV analysis. The motion directionality is shown by cos(θ) of the velocity vectors, and speed is the absolute value of velocities. As indicated by color, directionality (top) was largely similar across either WT (left) or Krt6a/Krt6b-null (right) cell sheets, indicating that the motion was mostly collective and that keratinocytes migrated as a sheet instead of groups of cells. Compared with Krt6a/Krt6b-null cells, WT cells were less coordinated in the first half time (before 8 h), but their coordination improved in the later times. Krt6a/Krt6b-null cells migrated faster ( Fig. 1 F) than WT cells, resulting in increased migration area as illustrated in Fig. 1 E.
