Wang Kai, Suyama Ritsuko, Mizutani Nanako, Matsuo Masaki, Peng Yu, Seki Masahide, Suzuki Yutaka, Luscombe Nicholas M, Dantec Christelle, Lemaire Patrick, Toyoda Atsushi, Nishida Hiroki, Onuma Takeshi A
Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai 200031, China.
Development. 2025 Mar 15;152(6). doi: 10.1242/dev.202666. Epub 2025 Mar 18.
The larvacean Oikopleura dioica is a fast-developing chordate because of its small number of cells (∼4500 in juveniles) and rapid development to complete morphogenesis by 10 h after fertilization. Strikingly, most of its blastomeres are restricted to give rise to a single cell-type by the 32-cell stage of embryogenesis, unlike cell fate determination at the 110-cell stage in ascidians. In this study, RNA-sequencing (RNA-seq) revealed non-canonical properties of O. dioica: (1) an initial zygotic gene expression of 950 genes at the 16- to 32-cell stage; (2) 25 transcription factors (TFs) are expressed in the 32-cell stage (fewer than half of the TFs underlying gene regulatory networks in ascidian embryogenesis were lost or not expressed); (3) five maternal mRNAs localized in the vegetal-posterior blastomeres in animal and vegetal hemispheres; and (4) three maternal mRNAs localized in the small vegetal pole region of unfertilized eggs. These observations indicate that this fast-developing chordate lacks the first phase of development in ascidians: fertilization-driven ooplasmic movements that drive postplasmic RNAs toward the vegetal pole. These data have been deposited in ANISEED (https://www.aniseed.fr/) as transcriptome resources.
幼虫尾海鞘（Oikopleura dioica）是一种发育迅速的脊索动物，因为其细胞数量较少（幼体约有4500个细胞），且在受精后10小时内就能快速发育完成形态发生。引人注目的是，与海鞘在110细胞阶段的细胞命运决定不同，在胚胎发育的32细胞阶段，其大多数卵裂球就已被限制只能产生单一的细胞类型。在本研究中，RNA测序（RNA-seq）揭示了尾海鞘的非典型特性：（1）在16至32细胞阶段有950个基因开始进行合子基因表达；（2）在32细胞阶段表达了25种转录因子（TFs）（在海鞘胚胎发育中构成基因调控网络的TFs中，丢失或未表达的不到一半）；（3）5种母体mRNA定位于动物半球和植物半球的植物后极卵裂球中；（4）3种母体mRNA定位于未受精卵的小植物极区域。这些观察结果表明，这种发育迅速的脊索动物缺乏海鞘发育的第一阶段：受精驱动的卵质运动，这种运动将胞质后RNA推向植物极。这些数据已作为转录组资源存入ANISEED（https://www.aniseed.fr/）。
