University of California-Berkeley, Departments of Molecular and Cell Biology, Integrative Biology, Center for Integrative Genomics, and HHMI, 3060 VLSB # 3140, Berkeley, CA 94720-3140, USA.
Dev Biol. 2010 May 1;341(1):256-66. doi: 10.1016/j.ydbio.2009.12.006. Epub 2009 Dec 21.
In Parhyale hawaiensis, the first three divisions are holoblastic and asymmetric, resulting in an embryo comprised of eight cells-four macromeres and four micromeres. Lineage studies performed at this stage demonstrate that the progeny of each cell contribute to specific portions of different germ layers. However, it is not known if this lineage pattern means a given blastomere is committed to its specific fate, indicative of mosaic development, or if regulation can occur between blastomere progeny so that the loss of a blastomere could be compensated for during development. Furthermore, if compensation occurs, what would be the source of such replacement? To investigate these possibilities, we performed ablation experiments at the eight-cell stage. We find that loss of blastomeres results in compensation. To determine the compensation pattern, we combined ablation and cell lineage tracing to reveal that progeny of mesoderm and ectoderm producing blastomeres display intra-germ layer compensation. Furthermore, by ablating lineages later in development, we identify a key interval between gastrulation and germband elongation after which compensation no longer occurs. Our results suggest that Parhyale possesses a mechanism to assess the status of mesoderm and ectoderm formation and alter development to replace the missing portions of these lineages.
在 Parhyale hawaiensis 中，前三个分裂是全裂的和不对称的，导致胚胎由八个细胞组成——四个大卵裂球和四个小卵裂球。在这个阶段进行的谱系研究表明，每个细胞的后代都有助于不同胚层的特定部分。然而，目前还不清楚这种谱系模式是否意味着一个特定的卵裂球被指定了特定的命运，是否表明是镶嵌发育，或者是否可以在卵裂球后代之间发生调节，以便在发育过程中可以补偿卵裂球的损失。此外，如果发生补偿，替代的来源是什么？为了研究这些可能性，我们在八细胞阶段进行了消融实验。我们发现，卵裂球的损失会导致补偿。为了确定补偿模式，我们将消融和细胞谱系追踪相结合，揭示了产生中胚层和外胚层的卵裂球的后代表现出胚层内补偿。此外，通过在发育后期消融谱系，我们确定了一个关键的间隔，即原肠胚形成和原肠胚伸长之后，补偿不再发生。我们的结果表明，Parhyale 拥有一种评估中胚层和外胚层形成状态的机制，并改变发育以替代这些谱系缺失的部分。
