Atomic force microscopic investigation on the potential early intermediate stages of fibrillogenesis of fibronectin within fibrils

To date, a large number of literature have focused on the mechanisms of fibronectin (FN) fibril initiation and elongation, discovering many binding sites on FN molecules that are required for FN fibril growth. However, it is still poorly understood how FN fibrils widen while elongating. Here, single molecules and polymers, FN fibrillogenesis, and FN fibril bundles around cells have all been investigated visually using atomic force microscopy. We found that the formation of ring-shaped and beaded-filament-like FN aggregates may be two early intermediate stages of FN fibrillogenesis within the fibrils away from cells, perhaps involving in the FN fibril widening/bundling.