Differential expression patterns of the tight junction-associated proteins occludin and claudins in secretory and mature ameloblasts in mouse incisor

Abstract

Tight junctions (TJs) function primarily as a barrier against paracellular transport between epithelial cells and are composed mainly of occludin (OLD) and claudins (CLDs). The CLD family consists of 24 members that show tissue- or cell-specific expression. Ameloblasts, which originate from the oral epithelium, form enamel, and enamel proteins and minerals are transported across the ameloblastic layer during amelogenesis. We immunohistochemically examined the distribution patterns of TJs in ameloblasts by observing the expression patterns of OLD and CLDs (CLD-1 to CLD-10). Secretory ameloblasts contained OLD and CLD-1, -8, and -9 at the distal end of the cell. In mature ameloblasts, OLD and CLD-1, -6, -7, -8, -9, and -10 were present mainly at both the distal and proximal ends of the cell, regardless of whether the ameloblasts were ruffle-ended or smooth-ended. Mature ameloblasts in which only the proximal ends were stained for OLD and CLDs were also found. These results indicate that the expression patterns of CLDs and the distribution patterns of TJs change drastically between the secretory and mature ameloblast stages, suggesting that these patterns reflect the different functions of these cells, specifically in the transport of proteins and ions for enamel formation.

Klf5 Mediates Odontoblastic Differentiation through Regulating Dentin-Specific Extracellular Matrix Gene Expression during Mouse Tooth Development

“…The similar results were observed by other groups2728293031. However, difference of the spatial and temporal distributions may be due to the animals used and tissue preparations as well as antibody concentrations and resources39. These data indicated that Klf5, Dspp and Dmp1 are involved in the odontoblastic differentiation and dentin formation.…”

Amelogenesis imperfecta in familial hypomagnesaemia and hypercalciuria with nephrocalcinosis caused byCLDN19gene mutations

“…At the secretory stage, ameloblasts become postmitotic, polarise and develop secretory machinery. They are organised as a single-cell layer with well-defined proximal and distal cell-cell junctions 4. They secrete a set of mineral-binding peptides, forming an extracellular compartment of organic matrix (mainly amelogenins, enamelin and ameloblastin) 5.…”

“…TJ core components are claudins, a family of proteins that includes more than 24 peptides. To date, nine claudins have been identified in the dental epithelium of various animal species and humans 4 22–27…”

Dentin sialoprotein facilitates dental mesenchymal cell differentiation and dentin formation

“…Expression of the TJ-associated proteins was clearly detected in odontoblasts, however, temporal and spatial distributions of these proteins such as Ocln in differentiating odontoblasts are different 48, 49, 55–58 . The cause of the differences is still uncertain, and it may be due to the animals used and the methods for specimen preparation as well as antibody concentrations in each study 59 . Lee et al observed that Ocln and ZO-1 proteins are strongly expressed in odontoblasts at PNs from 7 to 18 examined in the wild type mouse teeth whereas expression of Ocln and ZO-1 is hardly detected in odontoblasts of Nfic-deficient mice at the same ages.…”