Chen Shanduo, Gildor Tsvia, Tewari Prashant, Ben-Tabou de-Leon Smadar
Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel.
J Exp Zool B Mol Dev Evol. 2025 Aug 25. doi: 10.1002/jez.b.23326.
Biomineralization, the formation of mineralized tissues like skeletons and shells, is an essential developmental process in diverged phyla. Vertebrates' biomineralization involves the secretion of specialized extracellular matrix (ECM) proteins and the formation of Integrin-based focal adhesions, yet less is known about the role of such factors in invertebrates. A recent study has shown that focal adhesions form around the calcite spicule of the sea urchin larva, however, the skeletogenic expression and role of adhesion related proteins in this system are understudied. Here, we identified a set of ECM and adhesion genes that show enriched expression in the sea urchin skeletogenic cells and studied the role of the ECM protein, Npnt, in Paracentrotus lividus. The integrin alpha proteins, Pl-Ahi, Pl-Aji, Pl-Api, and the Pl-Talin protein are highly conserved between sea urchin and humans and the expression of these genes is enriched in the skeletogenic cells during early skeletogenesis. Pl-npnt is expressed specifically in skeletogenic cells throughout skeletogenesis and requires Vascular Endothelial Growth Factor (VEGF) signaling for its maintenance. Genetic perturbations of Pl-npnt result in skeletal defects, including reduced length of skeletal rods, ectopic spicule formation and branching, while skeletogenic cell migration remained unaffected. The activation of focal adhesion kinase (FAK) around the spicules is independent of Pl-Npnt activity in agreement with the loss of Integrin binding site in the sea urchin Npnt protein. Our findings set the stage for further analyses of ECM and adhesion-mediated mechanisms that drive sea urchin biomineralization, and most likely participate in skeletal development across metazoans.
生物矿化，即骨骼和贝壳等矿化组织的形成，是不同门动物中一个重要的发育过程。脊椎动物的生物矿化涉及特殊细胞外基质（ECM）蛋白的分泌以及基于整合素的粘着斑的形成，但对于这些因素在无脊椎动物中的作用了解较少。最近的一项研究表明，粘着斑在海胆幼虫的方解石骨针周围形成，然而，该系统中与粘着相关蛋白的骨骼生成表达和作用尚未得到充分研究。在这里，我们鉴定了一组在海胆骨骼生成细胞中表达丰富的ECM和粘着基因，并研究了ECM蛋白Npnt在紫球海胆中的作用。整合素α蛋白Pl-Ahi、Pl-Aji、Pl-Api和Pl-Talin蛋白在海胆和人类之间高度保守，并且这些基因的表达在早期骨骼生成过程中在骨骼生成细胞中富集。Pl-npnt在整个骨骼生成过程中特异性地在骨骼生成细胞中表达，并且其维持需要血管内皮生长因子（VEGF）信号传导。Pl-npnt的基因扰动会导致骨骼缺陷，包括骨骼杆长度缩短、异位骨针形成和分支，而骨骼生成细胞迁移不受影响。骨针周围粘着斑激酶（FAK）的激活独立于Pl-Npnt活性，这与海胆Npnt蛋白中整合素结合位点的缺失一致。我们的研究结果为进一步分析驱动海胆生物矿化的ECM和粘着介导机制奠定了基础，并且很可能参与后生动物的骨骼发育。
