The evolutionary origin of metazoan cell types such as neurons and muscles is not known. Using whole-body single-cell RNA sequencing in a sponge, an animal without nervous system and musculature, we identified 18 distinct cell types. These include nitric oxide–sensitive contractile pinacocytes, amoeboid phagocytes, and secretory neuroid cells that reside in close contact with digestive choanocytes that express scaffolding and receptor proteins. Visualizing neuroid cells by correlative x-ray and electron microscopy revealed secretory vesicles and cellular projections enwrapping choanocyte microvilli and cilia. Our data show a communication system that is organized around sponge digestive chambers, using conserved modules that became incorporated into the pre- and postsynapse in the nervous systems of other animals.

中文翻译：

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分析海绵中的细胞多样性为动物细胞类型和神经系统进化提供信息

神经元和肌肉等后生动物细胞类型的进化起源尚不清楚。在海绵中使用全身单细胞 RNA 测序，一种没有神经系统和肌肉组织的动物，我们确定了 18 种不同的细胞类型。这些包括一氧化氮敏感的收缩松果细胞、变形吞噬细胞和分泌神经样细胞，它们与表达支架和受体蛋白的消化软骨细胞密切接触。通过相关的 X 射线和电子显微镜对神经样细胞进行可视化显示，分泌性囊泡和细胞投射物包裹着软骨细胞微绒毛和纤毛。我们的数据显示了一个围绕海绵消化室组织的通信系统，使用的保守模块被整合到其他动物神经系统的突触前和突触后。