BOA, INRA, Université de Tours, 37380 Nouzilly, France.
Department of Innovation in Medical Education, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa K1H 8M5, Canada.
J Biol Chem. 2019 Oct 4;294(40):14526-14545. doi: 10.1074/jbc.RA119.009799. Epub 2019 Jul 29.
The avian eggshell is a critical physical barrier, which permits extra-uterine development of the embryo. Its formation involves the fastest known biomineralization process in vertebrates. The eggshell consists of proteins and proteoglycans that interact with the mineral phase to impart its specific microstructure and mechanical properties. In this study, we investigated the role of epidermal growth factor (GF)-like repeats and scoidin-ike domains 3 (EDIL3) and ilk at lobule-GF factor 8 (MFGE8), two glycoproteins that are consistently detected in eggshell proteomes. We verified their common evolutionary history and identified the timing of the duplication event giving rise to these two distinct proteins. / chromosomal locations revealed a nested syntenous relationship with other genes ( and ) that are also involved in vertebrate calcification. EDIL3 and MFGE8 proteins possess EGF-like and coagulation factor 5/8 (F5/8C) domains, and their 3D structures predicted that they bind calcium and extracellular vesicles. In chicken, we confirmed the presence of EDIL3 and MFGE8 proteins in eggshell, uterine fluid, and uterus. We observed that only is overexpressed in tissues in which eggshell mineralization takes place and that this overexpression occurs only at the onset of shell calcification. We therefore propose a model in which EDIL3 and, to a lesser extent, MFGE8 proteins guide vesicles containing amorphous calcium carbonate to the mineralization site. This model was supported by the observation that extracellular vesicles accumulate in uterine fluid during eggshell calcification and that they contain high levels of calcium, carbon, and oxygen that correspond to calcium carbonate.
禽蛋壳是一种至关重要的物理屏障，允许胚胎在子宫外发育。其形成涉及脊椎动物中已知最快的生物矿化过程。蛋壳由蛋白质和蛋白聚糖组成，它们与矿物质相互作用，赋予蛋壳特定的微观结构和机械性能。在这项研究中，我们研究了表皮生长因子 (EGF)-样重复和 scoidin-样结构域 3 (EDIL3)以及ilk at lobule-GF factor 8 (MFGE8)这两种糖蛋白在蛋壳蛋白质组中一直被检测到的作用。我们验证了它们共同的进化历史，并确定了导致这两种不同蛋白质产生的复制事件的时间。/染色体定位揭示了与其他参与脊椎动物钙化的基因（和）的嵌套同线性关系。EDIL3 和 MFGE8 蛋白具有 EGF 样和凝血因子 5/8 (F5/8C) 结构域，其 3D 结构预测它们可以结合钙和细胞外囊泡。在鸡中，我们证实了 EDIL3 和 MFGE8 蛋白存在于蛋壳、子宫液和子宫中。我们观察到仅在发生蛋壳矿化的组织中过度表达，并且这种过度表达仅在壳钙化开始时发生。因此，我们提出了一个模型，即 EDIL3 和在较小程度上 MFGE8 蛋白引导含有无定形碳酸钙的囊泡到达矿化部位。这一模型得到了如下观察结果的支持：在蛋壳钙化过程中，细胞外囊泡在子宫液中积累，并且它们含有高水平的钙、碳和氧，与碳酸钙相对应。
