Microridges in Cyprinus carpio scale epidermis

Abstract

Actin-based microridges were evaluated in koi scale epidermis in situ. The fingerprint-patterned microridges covered the dorsal face of superficial layer cells and were overall similar to that described in many fishes. Several other microridge patterns were observed, however, ranging from loose or tightly packed ridges, fragmented ridges, a honeycomb ridge pattern and the presence of actin-rich puncta.Individual F-actin-stained microridges varied greatly in length, from a few to 30 μm or more, with a few single ridges extending the entire perimeter of a cell. Branched microridges, comprised of single ridges that appeared continuous with each other, extended to over 150 μm in some cases. The actin-binding proteins α-actinin and cortactin were distributed in a dot-like pattern along the length of individual ridges, consistent with bundled actin cores described in earlier studies. Antiphosphotyrosine antibody failed to detect this signal transduction-related amino acid modification in microridges unless tyrosine phosphatases were first inhibited, after which bright phosphotyrosine-rich dots were detected along the microridges. K E Y W O R D Sactin microridges, koi, phosphotyrosine, signal transduction

Microridges are apical epithelial projections formed of F-actin networks that organize the glycan layer

“…Although, Arp2/3 complex inhibition had only a mild effect on the glycan layer, our TEM, SEM and WGA staining data as a whole suggests that glycans are enriched around microridges. WGA staining also follows the microridge pattern in the case of koi epidermal cells 39 . It is thus likely that the distance between microridges is an important factor in the organization of the glycan layer, which is corroborated by the fact that the glycan layer on the head, which has closely packed microridges, exhibits a dense and uniform organization as compared to that on the flank, where microridges are spaced apart.…”

“…Thus far, only a few actin-binding proteins are known to localize to the microridge. These include α-actinin, ezrin, myosin II, VASP and cortactin 9,11,13,34,39 . Since actin-binding proteins regulate and organize actin filaments into specific arrangements such as parallel or antiparallel bundles and branched networks 30,40 , we analyzed the localization of additional regulators of the actin cytoskeleton to microridges.…”

“…In order to visualize the glycan layer with a confocal microscope, we used a fluorescently tagged wheat germ agglutinin (WGA) lectin 39 . This approach revealed that the glycan layer was arranged around microridges (Fig.…”

Apical surface ring formation in Cyprinus carpio scale epidermis

“…Furthermore, WGA was also incorporated into the terminal bodies. WGA can bind n-acetylglucosamine residues in mucus and mucin granules (DePasquale, 2018;Hidalgo, Velasco, Sanchez Aguayo, & Amores, 1987;Leknes, 2011;Miyake, Tanaka, & McNeil, 2006), raising the likelihood that WGA-positive terminal bodies represent internalized skin mucus. The presence of ARs on the epidermal surface, coupled with the uptake of extracellular fluid and skin-adhered mucus, suggests a role for the rings in constantly sampling the surrounding water for free pathogens or toxins, or mucustrapped particulate pathogens which are then sequestered in the terminal body for eventual degradation and disposal.…”

Comparison of microridges in juvenile and adult sunfish, Lepomis gibbosus

“…A potential function frequently attributed to microridges is stabilization of the mucus layer that coats epithelia (Sperry & Wassersug, 1976), a characteristic that would likely be active in a wide range of mucosal tissue. Microridges may also provide protection from physical damage to the epidermis (Mittal et al, 2004), potentially serve as a reserve of pre-polymerized actin, that is, readily available for epidermal wound healing (Sharma, Anderson, & Muller, 2005), and have potential for signal transducing activity (DePasquale, 2018b).…”