Abstract：
The echinoderm nervous system has been studied as a model for understanding the evolution of the chordate nervous system. Neuronal cells are essential groups that release a \'cocktail\' of messenger molecules providing a spectrum of biological actions in the nervous system. Among echinoderms, most evidence on neuronal cell types has been obtained from starfish and sea urchin. In sea cucumbers, most research has focused on the location of neuronal cells, whereas their transcriptional features have rarely been investigated. Here, we observed the ultrastructure of neuronal cells in the sea cucumber, Apostichopus japonicus. The transcriptional profile of neuronal cells from the circumoral nerve ring (CNR) was investigated using single-cell RNA sequencing (scRNA-seq), and a total of six neuronal cell types were identified. 26 neuropeptide precursor genes (NPPs) and 28 G-protein-coupled receptors (GPCR) were expressed in the six neuronal cell types, comprising five NPP/NP-GPCR pairs. Unsupervised pseudotime analysis of neuronal cells showed their different differentiation status. We also located the neuronal cells in the CNR by immunofluorescence (IF) and identified the potential hub genes of key cell populations. This broad resource serves as a valuable support in the development of cell-specific markers for accurate cell-type identification in sea cucumbers. It also contributes to facilitating comparison across species, providing a deeper understanding of the evolutionary processes of neuronal cells.
摘要：
已经研究了棘皮动物神经系统作为理解脊索神经系统进化的模型。神经元细胞是必不可少的群体，它们释放出信使分子的“混合物”，在神经系统中提供一系列生物作用。在棘皮动物中，关于神经元细胞类型的大多数证据都来自海星和海胆。在海参中，大多数研究都集中在神经元细胞的位置，而它们的转录特征很少被研究。这里,我们观察了海参神经细胞的超微结构，刺参。使用单细胞RNA测序（scRNA-seq）研究了来自周围神经环（CNR）的神经元细胞的转录谱，共鉴定出六种神经元细胞类型。26个神经肽前体基因（NPPs）和28个G蛋白偶联受体（GPCR）在六种神经元细胞类型中表达，包含五个NPP/NP-GPCR对。神经元细胞的无监督假时间分析显示其不同的分化状态。我们还通过免疫荧光（IF）定位了CNR中的神经元细胞，并鉴定了关键细胞群的潜在枢纽基因。这种广泛的资源为开发用于海参中准确细胞类型鉴定的细胞特异性标记提供了宝贵的支持。它还有助于促进跨物种的比较，对神经元细胞的进化过程有更深入的了解。
