Shell matrix proteins have important roles in the biomineralization of shells. In this study, we isolated and identified a novel shell matrix protein gene, hic7, from the mussel Hyriopsis cumingii. The cDNA of hic7 was 459 bp long, including a 240-bp open reading frame. It encoded a 79 amino acid-long protein, with amino acids 1–19 constituting the signal peptide. The resulting hic7 is rich in cysteine (16.5%). After removing the signal peptide, the molecular weight was 8.85 kDa and the theoretical isoelectric point was 6.34, indicating that hic7 is a weakly acidic shell matrix protein. Hic7 is mainly expressed in the mantle tissue of H. cumingii. In situ hybridization showed hic7 signals at the edge and dorsal region of the mantle outer fold, indicating that it is related to the formation of the prismatic and nacreous layer of the shell. RNA interference indicated that when hic7 was inhibited by 80%, the crystal morphology of the prism and nacre layers of the shell were irregular and disordered. In addition, the expression of hic7 during the early development of the pearl sac indicated that it has an important role in the transformation of calcium carbonate crystals from a disordered to an orderly deposition pattern. These results suggest that matrix protein hic7 take part in constructing the framework of crystal nucleation and regulating the calcium carbonate crystal morphology of the nacreous and prismatic layers of shells and pearls.

壳基质蛋白在壳的生物矿化中具有重要作用。在这项研究中，我们从贻贝Hyriopsis cumingii 中分离并鉴定了一个新的壳基质蛋白基因hic7。hic7的 cDNA长 459 bp，包括一个 240 bp 的开放阅读框。它编码一个 79 个氨基酸长的蛋白质，其中氨基酸 1-19 构成信号肽。由此产生的 hic7 富含半胱氨酸 (16.5%)。去除信号肽后，分子量为8.85 kDa，理论等电点为6.34，说明hic7是弱酸性壳基质蛋白。Hic7主要在H. cumingii的地幔组织中表达。原位杂交显示hic7在地幔外褶皱的边缘和背侧区域发出信号，表明它与壳棱柱状和珠光层的形成有关。RNA干扰表明，当hic7被抑制80%时，壳棱柱和珍珠层的晶体形态不规则、无序。此外，hic7在珠囊发育早期的表达表明它在碳酸钙晶体从无序到有序沉积模式的转变中具有重要作用。这些结果表明，基质蛋白 hic7 参与构建了晶体成核框架并调节了贝壳和珍珠的珠光层和棱柱层的碳酸钙晶体形态。