Calcineurin subunit B is involved in shell regeneration inHaliotis diversicolor

Abstract

Abalone shells are mainly composed of two major polymorphs of CaCO3 that are distributed in different layers of the shell. The process of shell biomineralization is controlled by genes and proteins expressed within the mantle epithelium. In this present paper, we conducted a shell regeneration experiment to study the role of HcCNA and HcCNB (individual subunits of calcineurin) in shell biomineralization in H. diversicolor. The results of qPCR showed that HcCNB is upregulated to a greater extent than HcCNA in the mantle after shell notching. In vivo study of the effects of rHcCNB injection showed a significantly higher percentage of regenerated shell length, but not area, in the injected group compared to the control group. In addition, SEM observation of the inner surface of the regenerated shells revealed three different zones including prismatic, nacreous, and a distinct transition zone. Changes in the crystal organization and ultrastructure are clearly evident in these three zones, particularly after 3 weeks of rHcCNB administration. We hypothesize that this is due to faster biomineralization rates in the rHcCNB treated group. Taken together, our results demonstrate that HcCNB participates in shell regeneration in H. diversicolor. As calcineurin subunits have also been implicated in shell formation in bivalves, these findings suggest that calcineurin subunits may play important roles in biomineralization in all conchiferans.

The Mineralization of Molluscan Shells: Some Unsolved Problems and Special Considerations

“…Similarly, EP28, the most abundant EPF protein (account for half of the total EPF proteins) in Mytilus edulis is absent in the mussel shell, although it has calcium binding affinity and is supposed to participate in shell mineralization (Hattan et al, 2001). Very likely, these components, together with other biomineralization-related proteins such as Calmodulin (Li et al, 2005), Calcineurin (Buddawong et al, 2021) and ferritin (Varney et al, 2021) are involved in the metabolism of calcium and/or other ions. Alternatively, EPF proteins ACCBP and EP28 may inhibit undesired mineralization in the hemolymph and other body fluids considering their broad tissue distributions (Hattan et al, 2001;Ma et al, 2007).…”