Abstract
The growth of molluscan shell crystals is generally thought to be initiated from the extrapallial fluid by matrix proteins, however, the cellular mechanisms of shell formation pathway remain unknown. Here, we first report amorphous calcium carbonate (ACC) precipitation by cellular biomineralization in primary mantle cell cultures of Pinctada fucata. Through real-time PCR and western blot analyses, we demonstrate that mantle cells retain the ability to synthesize and secrete ACCBP, Pif80 and nacrein in vitro. In addition, the cells also maintained high levels of alkaline phosphatase and carbonic anhydrase activity, enzymes responsible for shell formation. On the basis of polarized light microscopy and scanning electron microscopy, we observed intracellular crystals production by mantle cells in vitro. Fourier transform infrared spectroscopy and X-ray diffraction analyses revealed the crystals to be ACC, and de novo biomineralization was confirmed by following the incorporation of Sr into calcium carbonate. Our results demonstrate the ability of mantle cells to perform fundamental biomineralization processes via amorphous calcium carbonate, and these cells may be directly involved in pearl oyster shell formation.
Highlights
Biomineralization refers to the process of hard tissue formation by organisms and has been characterized as a highly controlled and functional process [1]
The enzyme activities first peaked at 7.5 days prior to nucleation and growth of Amorphous calcium carbonate (ACC) and remained at high levels after 15 days of cell culture with ACC first appearing in the mantle cell at 15 days (Figure 4B)
The primary cell cultures from the pearl oyster Pinctada fucata displayed an increase in mineralization-related enzymes activities that was followed by ACC precipitation
Summary
Biomineralization refers to the process of hard tissue formation by organisms and has been characterized as a highly controlled and functional process [1]. The pearl oyster Pinctada fucata is one of the best-studied species with regard to biomineralization due to its intriguing shell microstructure, which consists of inner aragonitic nacreous and outer calcitic prismatic layers; in addition, Pinctada fucata is of economic importance to the pearl industry [2]. Organisms can produce stable spherical ACC particles, and the colloidal nanoparticles participate as transient intermediates in the formation of crystalline aragonite or calcite, such as in mollusc shells and sea urchins. Beniash et al have shown that ACC is present in the sea urchin larval spicule, which was the first documentation of the biological transformation of ACC into calcite [8]. ACC fulfills an important function in mollusc larval shell formation, and ACC has been reported in the adult shell [6]; the mechanism of the extracellular or intracellular transformation of ACC into aragonite remains unclear
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
