Apextrin, a novel extracellular protein associated with larval ectoderm evolution in Heliocidaris erythrogramma
Apextrin, a novel extracellular protein associated with larval ectoderm evolution in Heliocidaris erythrogramma
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DOI：
10.1006/dbio.1999.9283
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发表时间：
1999-07-01
影响因子：
2.7
通讯作者：
Raff, RA
中科院分区：
文献类型：
--
作者：
Haag, ES;Sly, BJ;Raff, RA
在海胆直接发育的进化过程中，主要的修饰发生了，这使得成体特异性结构的早熟形成，并导致新的幼虫体围绕这些结构。HeET-1基因是在红眼病早期胚胎中富集转录本的差异筛选中分离出来的，相对于间接发育的同系物结核。HeET-1在三个基因中是独一无二的，因为在结核总胚胎RNA印迹中没有检测到同源转录物。为了验证HeET-1基因在Heliocidaris中的这种明显的极端差异表达，我们从结核菌基因组DNA中分离出HeET-1同源物，并用它来探测从结核菌胚胎中制备的poly(a)(+) RNA的印迹。它在结核胚胎中的表达水平是这种技术无法检测到的。预测的HeET-1氨基酸序列表明它编码一种新的分泌蛋白。为了评估HeET-1的功能，我们建立了HeET-1编码蛋白的多克隆抗血清。我们发现它以一种分泌囊泡的形式存在于卵子中，并且这种母体池在受精后逐渐分泌。当细胞在囊胚中获得顶基极性时，该蛋白定位于顶细胞外基质，因此我们将其命名为apextrin。apex蛋白的顶端细胞外定位在幼虫外胚层的柱状细胞中保持，直到它们在变态时内化。进入的间质细胞在离开植物板后迅速内吞胞外蛋白。与纤维蛋白III（一种根尖层成分）的比较表明，纤维蛋白是一种细胞外蛋白，与质膜的联系比透明质层或根尖层紧密。我们认为apextrin参与了根尖细胞的粘附，其高水平的表达可能代表了一种适应性的选择，这是加强大红细胞膜胚胎所必需的。(C) 1999学术出版社。
During the evolution of direct development in the sea urchin Heliocidaris erythrogramma major modifications occurred, which allowed the precocious formation of adult-specific structures and led to a novel larval body that surrounds these structures. The HeET-1 gene was isolated in a differential screen for transcripts enriched in the early embryos of a erythrogramma relative to those of its indirect-developing congener, a tuberculata. HeET-1 was unique among the three genes found in that no homologous transcript was detected in a tuberculata total embryonic RNA blots. To verify this apparently extreme differential expression of the HeET-1 genes in Heliocidaris, we isolated the HeET-1 homologue from a tuberculata genomic DNA and used it to probe blots of poly(A)(+) RNA prepared from a tuberculata embryos. It is expressed in a tuberculata embryos at levels undetectable by this technique. The predicted amino acid sequence of HeET-1 suggested that it encodes a novel secreted protein. To assess the function of HeET-1, we raised polyclonal antisera to the HeET-1-encoded protein. We find that it is present in eggs in a type of secretory vesicle and that this maternal pool is gradually secreted after fertilization. As cells acquire apical-basal polarity in the blastula the protein becomes localized to the apical extracellular matrix, leading us to name the protein apextrin. The apical extracellular localization of apextrin is maintained in the columnar cells of the larval ectoderm until their internalization at metamorphosis. Ingressing mesenchyme cells rapidly endocytose apextrin upon leaving the vegetal plate. Comparison with fibropellin III, an apical lamina component, suggests that apextrin is an extracellular protein that is in tighter association with the plasma membrane than is the hyalin layer or apical lamina. We propose that apextrin is involved in apical cell adhesion and that its high level of expression may represent an adaptive cooption necessary for strengthening the large a erythrogramma embryo. (C) 1999 Academic Press.