Regulated cellular aggregation is an essential process for development and healing in many animal tissues. In some animals and a few distantly related unicellular species, cellular aggregation is regulated by diffusible chemical cues. However, it is unclear whether regulated cellular aggregation was part of the life cycles of the first multicellular animals and/or their unicellular ancestors. To fill this gap, we investigated the triggers of cellular aggregation in one of animals' closest unicellular living relatives--the filasterean Capsaspora owczarzaki. We discovered that Capsaspora aggregation is induced by chemical cues, as observed in some of the earliest branching animals and other unicellular species. Specifically, we found that calcium ions and lipids present in lipoproteins function together to induce aggregation of viable Capsaspora cells. We also found that this multicellular stage is reversible, as depletion of the cues triggers disaggregation, which can be overcome upon re-induction. Our finding demonstrates that chemically regulated aggregation is important across diverse members of the holozoan clade. Therefore, this phenotype was plausibly integral to the life cycles of the unicellular ancestors of animals.

中文翻译：

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化学因素在动物的近亲单细胞中诱导聚集多细胞性

受调节的细胞聚集是许多动物组织发育和愈合的重要过程。在一些动物和一些远缘单细胞物种中，细胞聚集受可扩散化学信号的调节。然而，尚不清楚受调节的细胞聚集是否是第一批多细胞动物和/或其单细胞祖先生命周期的一部分。为了填补这一空白，我们研究了动物最亲近的单细胞活体亲属之一——丝状菌 Capsaspora owczarzaki 中细胞聚集的触发因素。正如在一些最早的分支动物和其他单细胞物种中观察到的那样，我们发现荚膜聚集是由化学信号诱导的。具体来说，我们发现存在于脂蛋白中的钙离子和脂质共同作用以诱导活荚膜细胞的聚集。我们还发现这个多细胞阶段是可逆的，因为线索的耗尽会触发解聚，这可以在重新诱导时克服。我们的发现表明，化学调节聚集在全息动物进化枝的不同成员中很重要。因此，这种表型可能是动物单细胞祖先生命周期中不可或缺的一部分。