Ivanina Anna V, Falfushynska Halina I, Beniash Elia, Piontkivska Helen, Sokolova Inna M
Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.
Department of Human Health, I.Ya. Horbachevsky Ternopil State Medical University, Ternopil 46000, Ukraine.
J Exp Biol. 2017 Sep 15;220(Pt 18):3209-3221. doi: 10.1242/jeb.160861. Epub 2017 Jun 30.
The molluscan exoskeleton (shell) plays multiple important roles including structural support, protection from predators and stressors, and physiological homeostasis. Shell formation is a tightly regulated biological process that allows molluscs to build their shells even in environments unfavorable for mineral precipitation. Outer mantle edge epithelial cells (OME) and hemocytes were implicated in this process; however, the exact functions of these cell types in biomineralization are not clear. Pacific oysters () were used to study differences in the expression profiles of selected biomineralization-related genes in hemocytes and mantle cells, and the functional characteristics of hemocytes such as adhesion, motility and phagocytosis. The specialized role of OME in shell formation was supported by high expression levels of the extracellular matrix (ECM) related and cell-cell interaction genes. Density gradient separation of hemocytes revealed distinct phenotypes based on the cell morphology, gene expression patterns, motility and adhesion characteristics. These hemocyte fractions can be categorized into two functional groups, i.e. biomineralization and immune response cells. Gene expression profiles of the putative biomineralizing hemocytes indicate that in addition to their proposed role in mineral transport, hemocytes also contribute to the formation of the ECM, thus challenging the current paradigm of the mantle as the sole source of the ECM for shell formation. Our findings corroborate the specialized roles of hemocytes and the OME in biomineralization and emphasize complexity of the biological controls over shell formation in bivalves.
软体动物的外骨骼（贝壳）发挥着多种重要作用，包括结构支撑、抵御捕食者和应激源以及生理稳态维持。贝壳形成是一个受到严格调控的生物学过程，使软体动物即使在不利于矿物质沉淀的环境中也能构建其贝壳。外套膜边缘上皮细胞（OME）和血细胞参与了这一过程；然而，这些细胞类型在生物矿化过程中的确切功能尚不清楚。本研究使用太平洋牡蛎（）来探究血细胞和外套膜细胞中选定的生物矿化相关基因的表达谱差异，以及血细胞的黏附、运动和吞噬等功能特性。细胞外基质（ECM）相关基因和细胞间相互作用基因的高表达水平支持了OME在贝壳形成中的特殊作用。通过密度梯度分离血细胞，根据细胞形态、基因表达模式、运动和黏附特性揭示了不同的表型。这些血细胞组分可分为两个功能组，即生物矿化细胞和免疫反应细胞。推测的参与生物矿化的血细胞的基因表达谱表明，血细胞除了在矿物质运输中发挥作用外，还参与ECM的形成，从而挑战了目前认为外套膜是贝壳形成过程中ECM唯一来源的范式。我们的研究结果证实了血细胞和OME在生物矿化中的特殊作用，并强调了双壳贝类贝壳形成过程中生物调控的复杂性。
