Kawamura Kaz, Satoh Noriyuki
Department of Applied Science, Kochi University, Kochi 780-8520, Japan,
Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan,
Zoolog Sci. 2024 Dec;41(6):496-508. doi: 10.2108/zs240032.
Due to limited spawning seasons, embryogenesis of corals has not fully been studied and the embryonic origin of gastrodermis remains uncertain in . We herein examined how embryonic endodermal cells develop into the gastrodermis and mesentery of polyps in . In juvenile polyps, the gastrodermis invaginates to form mesenteries, both of which were stained with rhodamine-phalloidin, an anti-myocyte-specific enhancer factor 2 (anti-AtMef2) antibody, and an anti-lipoxygenase homology domain-containing protein 1 (anti-AtLoxhd1) antibody. Rhoda-mine-phalloidin staining was traced back to the endodermal cells of 60-85 hpf 'pear'-stage embryos through the larval stage. AtMef2 appeared in the blastomeres of a 12-hpf 'prawnchip'-stage embryo that was a variant U-shaped blastula with a narrow blastocoel. AtMef2 temporarily disappeared from the nuclei of 28-hpf 'donut'-stage embryos and reappeared in the endodermal cells of 40-hpf early 'pear'-stage embryos, suggesting a transition from maternal to zygotic expression of Mef2. The blastopore closed without the invagination of blastomeres. The gastrocoel collapsed and the Mef2-positive endoderm was dissociated into single cells in the well-developed blastocoel filled with yolk cells. The mesoglea appeared in the yolk cell layer. AtLoxhd1 was traced back to the endodermal cells of 'pear'-stage embryos. In 11-dpf larvae, Loxhd1-positive endodermal cells elongated in the vicinity of the mesoglea to adhere to each other and form the gastroderm epithelium in larvae. Therefore, in this coral, the inner wall of U-shaped early embryos is the cellular origin of the gastrodermis. Inner wall-derived endodermal cells move independently toward the mesoglea, where cell-cell adhesion occurs to establish the gastrodermis.
由于珊瑚的繁殖季节有限，其胚胎发育尚未得到充分研究，并且珊瑚胃层的胚胎起源仍不明确。我们在此研究了珊瑚胚胎内胚层细胞如何发育成水螅体的胃层和隔膜。在幼年水螅体中，胃层内陷形成隔膜，二者均被罗丹明 - 鬼笔环肽、抗肌细胞特异性增强子因子2（抗AtMef2）抗体和抗含脂氧合酶同源结构域蛋白1（抗AtLoxhd1）抗体染色。罗丹明 - 鬼笔环肽染色通过幼虫阶段追溯到60 - 85小时胚胎期“梨形”胚胎的内胚层细胞。AtMef2出现在12小时胚胎期“虾片”阶段胚胎的卵裂球中，该胚胎是具有狭窄囊胚腔的变异U形囊胚。AtMef2在28小时胚胎期“甜甜圈”阶段胚胎的细胞核中暂时消失，并在40小时早期“梨形”阶段胚胎的内胚层细胞中重新出现，这表明Mef2从母源表达向合子表达的转变。胚孔闭合时没有卵裂球内陷。原肠腔塌陷，Mef2阳性内胚层在充满卵黄细胞的发育良好的囊胚腔中解离成单个细胞。中胶层出现在卵黄细胞层中。AtLoxhd1追溯到“梨形”阶段胚胎的内胚层细胞。在11日龄幼虫中，Loxhd1阳性内胚层细胞在中胶层附近伸长并相互粘附，形成幼虫的胃层上皮。因此，在这种珊瑚中，U形早期胚胎的内壁是胃层的细胞起源。内壁来源的内胚层细胞独立地向中胶层移动，在那里发生细胞间粘附以形成胃层。
