Shimoda Marine Research Center, University of Tsukuba, 5-10-1, Shimoda, Shizuoka, 415-0025, Japan.
Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
Dev Biol. 2023 Jun;498:26-34. doi: 10.1016/j.ydbio.2023.03.005. Epub 2023 Mar 23.
The control of cell numbers and the establishment of cell types are two processes that are essential in early embryonic development. We have a reasonable understanding of how these processes occur individually, but we have considerably less sophisticated understanding of how these processes are linked. Tunicates have fixed cell lineages with predictable cell cycles, making them well suited to investigate these processes. In the ascidian Ciona, we show that the transcription factor Zic-r.b, known to be involved in establishing several cell types in early development also activates the expression of the cell cycle inhibitor CDKN1B. Zic-r.b is a major missing component of the cell division clock establishing specific cell numbers. We also show that a larvacean homolog of Zic-r.b is expressed one cell cycle earlier than its Ciona counterpart. The early expression in larvaceans may explain why they have half as many notochord cells as ascidians and may illustrate a general mechanism to evolve changes in morphology.
细胞数量的控制和细胞类型的建立是早期胚胎发育中两个必不可少的过程。我们对这些过程如何单独发生有一定的了解，但对这些过程是如何联系起来的了解甚少。被囊动物具有固定的细胞谱系和可预测的细胞周期，使它们非常适合研究这些过程。在尾海鞘 Ciona 中，我们发现转录因子 Zic-r.b，已知其参与早期发育中几种细胞类型的建立，也激活细胞周期抑制剂 CDKN1B 的表达。Zic-r.b 是建立特定细胞数量的细胞分裂时钟的主要缺失成分。我们还表明，Zic-r.b 的尾海鞘同源物的表达比其 Ciona 对应物早一个细胞周期。在尾海鞘中的早期表达可能解释了为什么它们的脊索细胞数量只有尾索动物的一半，并可能说明了一种用于进化形态变化的一般机制。
