Macropinocytosis Generates New Microridge Patterns in Fish Epidermis Cells

ABSTRACT Actin‐based microridges are fingerprint‐like patterned protrusions located on the apical surface of fish epidermal cells. Originally believed to be static structures microridges are now known to be dynamic entities that form from individual substructures, actin puncta, or from annealing of smaller established ridges into larger ones. Conversely, larger ridges can fragment into smaller segments or even be reduced to puncta. Cellular processes such as cytokinesis can physically alter microridge patterns, reducing these structures to individual puncta which then reassemble into microridges upon completion of cell division. Apical Rings are circular macropinocytotic structures constitutively active at the surface of fish epidermis, causing local disruption of the microridge pattern. The present study demonstrates that after macropinocytosis, different patterns are generated upon assembly of new microridges. Microridge patterns remain relatively stable in the absence of macropinocytotic activity. The results suggest that constitutive macropinocytotic activity has the potential to create entirely new microridge patterns.