Fig. 7

Collagen fibrils can grow along or co-aligned with existing fibrils. (A) Frames from an mNG-Col1α2 fibril deposition movie showing growth of collagen fibrils along existing fibrils with potential bundling and increase in signal intensity. Blue, green and red arrows indicate the end of a growing fibril as it passes along an existing fibril observed as a progressive increase in intensity. Scale = 5 μm. (B) Three frames taken from movie in A demonstrating three events of “on fibril” or coaligned fibril growth and bundling. Line plots of red line show the intensity and width of the fibril increasing over time (red selected early frame, green selected mid frame and blue selected late frame). (C) Time intensity plot of the red box zone in A shows the three events when a fibril travels along the underlying existing fibril. Events marked with a black arrow. (D) The direction increase in fibril intensity as a second fibril growth along another is illustrated with the use of colour coding (intensity based Look Up Table). (E) Frames from an mNG-Col1α2 fibril deposition movie showing a bifurcation event. Site of bifurcation highlighted by black arrow. The bifurcation event occurs within the black box. Images were acquired at 5 min intervals 12 frames per hour. Time stamps are included on each frame. Scale = 2 μm. (F) Selected frames from an mNG-Col1α2 fibril deposition movie showing a zippering event. The zippering occurs within the black box. Black arrow shows the direction of movement/zippering where two separate fibrils start to bundle/zipper from the bottom of the frame snapping together in the direction of the arrow.