Cleavage pattern, gastrulation, and neurulation in the appendicularian, Oikopleura dioica
Cleavage pattern, gastrulation, and neurulation in the appendicularian, Oikopleura dioica
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DOI：
10.1007/s00427-008-0205-4
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发表时间：
2008-02-01
影响因子：
2.4
通讯作者：
Nishida, Hiroki
中科院分区：
文献类型：
--
作者：
Fujii, Setsuko;Nishio, Takaya;Nishida, Hiroki
阑尾动物 Oikopleura dioica 是脊索动物。它的生命周期极短，大约只有5天，并且终其一生都保持着蝌蚪形状和尾巴的跳动。蝌蚪在 20 摄氏度下发育 3 小时后孵化。在这里，我们描述了原肠胚形成和神经形成过程中的分裂模式和形态发生细胞运动。裂解显示出不变的模式。它基本上是双侧的，但从四细胞阶段开始也显示出各种轻微的左右不对称。我们观察到后极的后植物 B 系细胞有两轮不等的分裂。不等分裂的性质让人想起海鞘胚胎中的分裂，并表明存在中心体吸引体，这是后极的特殊亚细胞结构。本报告中细胞分裂模式的表示将有助于识别每个细胞，这是阐明早期胚胎中基因表达模式的先决条件。原肠胚形成早在32细胞阶段就开始并分三个阶段进行。到第二阶段结束时的64细胞阶段，每个植物细胞都已进入胚胎，而动物细胞则通过外延覆盖整个胚胎。没有形成弓形体。在前部区域，8 个 A 线细胞沿前后轴排列为 2x4 阵列，并在 64 细胞阶段被内化。该过程被认为对应于神经形成。 Oikopleura 的简单和加速发育，尽管产生了保守的脊索动物身体计划，有利于使用分子和遗传学方法研究发育机制，并使这种动物成为脊索动物门中最简单的模式生物。
The appendicularian, Oikopleura dioica is a chordate. Its life cycle is extremely short-approximately 5 days-and its tadpole shape with a beating tail is retained throughout entire life. The tadpole hatches after 3 h of development at 20 degrees C. Here, we describe the cleavage pattern and morphogenetic cell movements during gastrulation and neurulation. Cleavage showed an invariant pattern. It is basically bilateral but also shows various minor left-right asymmetries starting from the four-cell stage. We observed two rounds of unequal cleavage of the posterior-vegetal B-line cells at the posterior pole. The nature of the unequal cleavages is reminiscent of those in ascidian embryos and suggests the presence of a centrosome-attracting body, a special subcellular structure at the posterior pole. The representation of the cell division pattern in this report will aid the identification of each cell, a prerequisite for clarifying the gene expression patterns in early embryos. Gastrulation started as early as the 32-cell stage and progressed in three phases. By the end of the second phase at the 64-cell stage, every vegetal cell had ingressed into the embryo, and animal cells had covered the entire embryo by epiboly. There was no archenteron formation. In the anterior region, eight A-line cells were aligned as a 2x4 array along the anterior-posterior axis and become internalized during the 64-cell stage. This process was considered to correspond to neurulation. The simple and accelerated development of Oikopleura, nevertheless giving rise to a conserved chordate body plan, is advantageous for studying developmental mechanisms using molecular and genetic approaches and makes this animal the simplest model organism in the phylum Chordata.