Fluorescence visualization of branchial collagen columns embraced by pillar cells.

A collagen column is a structure of the extracellular matrix that helps to maintain the flatness and width of gill lamella. Collagen columns are unique in that they are enfolded by plasma membrane of pillar cells that form two-dimensional vascular networks between parallel sheets of respiratory epithelia. Despite their unique structure and fundamental importance in the physiology of aquatic animals, little is known about their properties and molecular components, owing to the lack of detection methods. In this study we demonstrated that collagen columns can be visualized by staining with fluorescence-labeled concanavalin A (ConA), a lectin that specifically recognizes the trimannoside core of N-glycosylated proteins and histidine-tagged green fluorescent protein (His(6)-Xpress-GFP), a fluorescent substrate for transglutaminase. We constructed a three-dimensional image of a pillar cell and visualized the spatial relationship between collagen columns and contractile apparatuses within the pillar cell body. This manuscript contains online supplemental material at (www.jhc.org). Please visit this article online to view these materials.