Fine structural and immunohistochemical detection of collar enamel in the teeth of Polypterus senegalus, an actinopterygian fish

Abstract

This is the first detailed report about the collar enamel of the teeth of Polypterus senegalus. We have examined the fine structure of the collar enamel and enamel organ of Polypterus during amelogenesis by light and transmission electron microscopy. An immunohistochemical analysis with an antibody against bovine amelogenin, an antiserum against porcine amelogenin and region-specific antibodies or antiserum against the C-terminus, middle region and N-terminus of porcine amelogenin has also been performed to examine the collar enamel matrix present in these teeth. Their ameloblasts contain fully developed Golgi apparatus, rough endoplasmic reticulum and secretory granules. During collar enamel formation, an amorphous fine enamel matrix containing no collagen fibrils is found between the dentin and ameloblast layers. In non-demineralized sections, the collar enamel (500 nm to 1 μm thick) is distinguishable from dentin, because of its higher density and differences in the arrangement of its crystals. The fine structural features of collar enamel in Polypterus are similar to those of tooth enamel in Lepisosteus (gars), coelacanths, lungfish and amphibians. The enamel matrix shows intense immunoreactivity to the antibody and antiserum against mammalian amelogenins and to the middleregion- and C-terminal-specific anti-amelogenin antibodies. These findings suggest that the proteins in the enamel of Polypterus contain domains that closely resemble those of bovine and porcine amelogenins. The enamel matrix, which exhibits positive immunoreactivity to mammalian amelogenins, extends to the cap enameloid surface, implying that amelogenin-like proteins are secreted by ameloblasts as a thin matrix layer that covers the cap enameloid after enameloid maturation.

Immunohistochemical and Western blot analyses of collar enamel in the jaw teeth of gars,Lepisosteus oculatus, an actinopterygian fish

“…In Lepisosteus, immunolabeling by antibodies against mammalian amelogenin was detected in the granules of ameloblasts, but not in the enameloid matrix, during the enameloid mineralization stage prior to enameloid maturation and collar enamel formation, which implied that the ameloblasts were able to produce amelogenin-like proteins throughout odontogenesis, but only released these proteins during the collar enamel formation stage (7,30). In Polypterus, a basic actinopterygian, a thin film-like covering that exhibited immunoreactivity to anti-mammalian amelogenin antibodies was found on the surface of enameloid during the collar enamel formation stage, suggesting that ameloblasts secrete amelogenin-like proteins onto the surface of mature enameloid during the final stage of odontogenesis (5). No such covering was seen in the present study.…”

“…After the rabbits had been inoculated, their blood was harvested, and their serum was isolated by centrifugation. Antibodies against synthetic peptides containing the C-terminal segment (residues 158-173) or the middle segment (residues 63-75) of porcine amelogenin ( Figure 1) were raised in rabbits by intradermally injecting them with the synthesized antigen peptides coupled with bovine serum albumin (BSA), as described previously (5,23). After the rabbits had been injected with the above molecules, their blood was harvested, and their serum was isolated by centrifugation.…”

“…The members of Lepisosteus, a genus of living actinopterygian fish, which are commonly referred to as gars or garpikes, are reported to possess collar enamel (3,4). As few extant actinopterygian fish species possess collar enamel (5) and no marked enamel layer is found in the teeth of modern chondrichthyes, Lepisosteus is probably one of the most suitable genera for studying primitive enamel. However, there have been only a few studies of collar enamel in Lepisosteus (3,4), although a number of studies have examined tooth development in this genus (6)(7)(8).…”

Histological Observation of the Jaws and Teeth of the Green Spotted Pufferfish<i> (Tetraodon Nigroviridis)</i>

“…The dermal tooth (placoid scale) covering the body surface of sharks, cartilaginous fish, is considered to be the origin of the teeth of mammals including humans 1) , and many reports on the evolutionary process connecting sharks and humans have been published [2][3][4][5][6] . The crown surface of mammalian teeth contains epithelial enamel, whereas the teeth of most fish contain enameloid, which is structurally different from enamel, and studies to investigate fish teeth to clarify the evolution of enamel are considered necessary [7][8][9][10] . On the other hand, fish are used for genetic and embryological studies because they are easy to maintain compared to mammals, the time to reach sexual maturity is short, they are prolific and many samples can be collected at one time, and embryos are transparent throughout the course from eggs to hatching, making observation and experiments easy.…”

Immunohistochemical and Western Blotting Analyses of Ganoine in the Ganoid Scales of Lepisosteus oculatus: an Actinopterygian Fish

“…In polypterids, these scales mainly consist of three layers, a bony plate, dentin, and ganoine, whereas living lepisosteids lack the dentin layer (Sire, , ). Lepisosteus and Polypterus also have typical teeth composed of dental hard tissues, that is, dentin constituting the body of the tooth, and two kinds of well‐mineralized covering, cap enameloid and collar enamel (Ishiyama et al., ; Sasagawa et al., , ). Therefore, these species might be a suitable model for examining the relationship between teeth and ganoid scales.…”