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Calcium transport from the environment to the final site of mineral deposition involves uptake from the water or the food into cells. Within the cells calcium ions are translocated to various organelles and vesicles where they accumulate, in such a way as to not raise the very low calcium concentrations in the cytosol. In various biomineralizing systems, the calcium is stored in vesicles as a highly disordered hence relatively soluble solid phase. The concentrated calcium phase is then translocated out of the cell to the site of mineralization. Additional pathways may involve transport through the vasculature as ions and possibly mineral from distant sites. Understanding calcium pathways is the foundation for not only better understanding biomineralization processes but also for better understanding calcium and its fundamental role in cell signaling.

In barnacle shell, the calcified shell layer is laid on top of the epicuticle. Here, we report our strategy and some preliminary results on the identification of potential shell proteins of the barnacle . At first, proteins from acid-soluble and acid-insoluble shell extracts were subjected to proteomic analysis and searched against complete transcriptome. Then using the information that the calcified shell is formed just after the larval-adult molt, juvenile differentially expressed genes against larval stages were screened. Sixty secretory protein sequences were identified as primary candidates of shell proteins, among which 37 are novel proteins.

The characteristics of a cultured pearl are influenced by two kinds of pearl oysters. One is the donor pearl oyster, which provides a small piece of mantle to be transplanted, and the other is the recipient pearl oyster, in which the pearl nucleus and a small piece of mantle are transplanted. Generally, the brightness, luster, and color of pearls are affected by the donor oyster, while the thickness of nacre is affected by the recipient oyster. Previously, we have indicated that the sex of recipient pearl oyster directly affects the quality of pearl, and the optical characteristics measured by FT-IR (Fourier transform infrared spectroscopy) of pearl produced from male and female pearl oysters significantly differ (Iwai et al. Aquaculture 437:333–338, 2015). Moreover, using the various strains of Akoya pearl oyster as recipient and the same donor oyster, the produced Akoya pearl had different spectra for each strain. Also, besides the culture of the Akoya pearl oyster, the transplantation also produced different optically characterized pearls by breeding them in various environments. These results suggested that the optical characteristics underlying pearl quality are not only the influence by donor oyster but also the sex, the strain, and the breeding conditions of recipient oyster.

Minerals and vitamins affect bone formation, genetics, nutrition, and hormones. Studies mainly focus on the elucidation of the metabolic pathways during biomineralization to get an idea of how to promote the process of biomineralization in vivo and in vitro. One qualified approach to reach this is to investigate the influence of different substances on the proliferation and differentiation of osteoblastic cell cultures in vitro. The aim of this study was to investigate the effects of different types of single B vitamins (B, B, and B) and a vitamin B complex (B, B, B, B, B, B, and B) on proliferation and differentiation of primary bovine osteoblastic cells in vitro. The proliferation of osteoblastic cells during the experiments was evaluated by cell number analysis while cultivating. The expression of marking proteins of the osteogenic differentiation was evaluated by immunohistochemistry. Previous experiments with seven different B vitamins in different concentrations revealed a positive effect on cell proliferation with increasing concentration caused by three B vitamins: pyridoxal (B), folic acid (B), and cobalamine (B). The use of vitamin B, B, and B in different concentrations resulted in a significant increase of cell proliferation But neither the B vitamins nor the B vitamin complexes stimulated the expression of the typical bone cell proteins.

Biologically formed amorphous silica (biosilica) is widely found in diatoms, marine sponges, terrestrial plants, and bacteria, some of which have been well characterized. Although rice plants produce large amounts of biosilica (plant opal) in their leaf blades and rice husks, the molecular mechanism of biomineralization is still poorly understood. In the present study, we investigated the fundamental properties of plant opal in leaf blades of the rice plants () by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy. The number of fan-shaped plant opal increases in the motor cells (bubble-shaped epidermal cells) during heading time. High-resolution SEM analysis revealed that the plant opals are composed of nanoparticles, as is the case with diatom silica and siliceous spicule of sponge. Organic matrices in biominerals have been considered to control mineralization. Biosilicas in diatom and marine sponge are formed under ambient conditions using organic matrices, unique proteins, and long-chain polyamines. In this study, we report the establishment of purification method of plant opals from rice leaf blades. Finally, we succeeded in extracting organic matrices from the purified plant opal.

Extracellular matrix of bone and dentin is highly complex and involves a dynamic process of deposition and removal. Cells are the main architect that build this designer matrix that is highly specialized to calcified tissues. Osteoblasts or odontoblasts secrete both collagen and noncollagenous proteins in a temporal and spatial manner. Type I collagen self-assembles and forms a fabric-like template onto which noncollagenous proteins and mineral bind in a well-regulated manner. Dentin matrix protein 1 (DMP1) is one such noncollagenous protein that contains several acidic groups that can bind calcium ions which in turn binds phosphate and initiates the calcification process. In this study, we demonstrate that DMP1 is localized at specific sites on the self-assembled collagen matrix of dentin. In vitro nucleation studies on demineralized and deproteinized dentin slice adsorbed with DMP1 show bundles of well-ordered needle-shaped nanohydroxyapatite deposited on the dentin matrix. The nucleated mineral structures had uniform length and width and their long axis was oriented parallel to the collagen fibril axis. Overall, the physiologically self-assembled collagen and DMP1 mediated ordered deposition of nanocrystalline HAP.

Silicatein is the first protein isolated from the silicon biominerals and characterized as constituent of the axial filament in the silica spicules of the demosponge , by significant sequence similarity with cathepsin L, an animal lysosomal protease, and as a catalyst of silica polycondensation at neutral pH and room temperature. This protein was then identified in a wide range of the class Demospongiae and in some species of the class Hexactinellida. Our attempt to isolate silicatein from the silica skeleton of was unsuccessful, but instead we discovered glassin, a protein directing acceleration of silica polycondensation and sharing no significant relationship with any proteins including silicatein. The present study aims to verify the existence of silicatein by exploring the whole genome DNA sequence database of with the sequence similarity search. Although we identified the sequences of glassin, cathepsin L and chitin synthetase, an enzyme synthesizing chitin, which has already been found in the silicon biominerals in , silicatein failed to be identified. Our result indicates that silicatein is not essential for poriferan silicon biomineralization in the presence of glassin.

Various secretory calcium-binding phosphoprotein (SCPP) genes are involved in the formation of the bone, dentin, enamel, and enameloid in bony vertebrates. By contrast, no SCPP gene is found in cartilaginous vertebrates. In order to explain this difference, I investigated the origin and early evolution of SCPP genes. First, I examined the phylogeny of -family genes that include evolutionary precursors of SCPP genes. Then, I analyzed the genomic arrangement of the SCPP genes and three -family genes, , , and . The results are consistent with our previous hypothesis that an SCPP gene-like structure arose in the 5′ half of in a common ancestor of jawed vertebrates, at about the same time as the origin of mineralized skeleton. It is possible that cartilaginous vertebrates secondarily lost early SCPP genes, while bony vertebrates gained various new SCPP genes. Some of these new SCPP genes appear to have specifically involved in scale formation; however, these scale genes were lost in tetrapods.

Tooth enameloid in bony fish is a well-mineralized tissue resembling enamel in mammals. It was assumed that the dental epithelial cells are deeply involved in the formation of enameloid. However, unlike enamel matrix which fully consists of several ectodermal enamel matrix proteins (EMPs), whether enameloid matrix contains ectodermal EMPs has been debated for a long time. In the present study, transmission electron microscopy-based immunohistochemical examinations, using the protein A-gold method with antibodies and antiserum against mammalian amelogenin, were performed in order to search for EMP-like proteins in the cap enameloid of basic actinopterygians, and gar. Positive immunoreactivity was detected in the cap enameloid matrix just before the appearance of many crystallites along collagen fibrils, indicating that the cap enameloid contains EMP-like proteins. Immunolabelling was usually found along the collagen fibrils but was not seen on the electron-dense fibrous structures. Therefore, it is conceivable that the ectodermal EMP-like proteins in cap enameloid are involved in crystallite formation along collagen fibrils.

Cyclical ontogenetic changes of shell microstructures have been observed in the subfamily Anadarinae (Mollusca: Bivalvia, Arcidae) including fossil taxa. The changes in the bloody clam are controlled by temperature, which fluctuates seasonally, and can be used to determine the age of the individuals and to reconstruct paleoenvironments. In this study, samples of from eight localities covering broad geographical regions at various latitudes in Japan, Korea, and Russia were examined to assess the utility of time series variations in microstructures for paleoenvironmental and paleoecological studies. All specimens showed cyclical changes in the relative thickness of the composite prismatic and crossed lamellar structures in the outer layer with ontogenetic progression, and thus, this feature can be used as a proxy for water temperature of their habitats. Specimens from southern latitudes showed higher annual shell growth rates than northern specimens, suggesting that low temperatures arrest shell growth in and play a key role in determining the longevity and body size in . In long-lived individuals from the four northernmost localities, the relative thickness of the composite prismatic structure tended to decrease as the individuals aged, which may be a consequence of declining physiological activity, such as organic matrix secretion.