小柯机器人

美国加州大学Karthik Shekhar和美国哈佛大学Joshua R. Sanes共同合作，近期取得重要工作进展。他们研究提出了脊椎动物视网膜中神经元细胞类别和类型的演化。相关研究成果2023年12月13日在线发表于《自然》杂志上。

据介绍，视网膜的基本结构在脊椎动物中是保守的，而物种在视觉需求上有着很大的差异。视网膜细胞类型可能已经演化以适应这些不同的需求，目前还没有得到系统的研究。

研究人员生成并整合了17个物种的视网膜单细胞转录组图谱：人类、两种非人灵长类动物、四种啮齿类动物、三种有蹄类动物、负鼠、雪貂、树鼩、一种鸟类、一种爬行动物、一种硬骨鱼和一种七叶树。研究人员发现了六类视网膜细胞（光感受器、水平细胞、双极细胞、无长突细胞、视网膜神经节细胞（RGC）和米勒胶质细胞）具有的高度的分子保守性，不同物种的转录组差异与演化距离有关。主要的亚类也是保守的，而类或亚类内细胞类型之间的变化更为明显。

然而，一项综合分析显示，基于可能追溯到早期祖先脊椎动物的保守基因表达程序，许多细胞类型在不同物种之间是共享的。从外视网膜（光感受器）到内视网膜（RGC），细胞类型之间的差异程度增加，这表明演化优先影响视网膜输出。最后，研究人员确定了啮齿类动物侏儒视网膜神经节细胞（midget RGC）的直系同源物，其在人类视网膜中占RGC的80%以上，有助于提高视觉灵敏度，以前被认为仅限于灵长类动物。相比之下，小鼠同源物具有较大的接受野，约占小鼠RGC的2%。灵长类动物和小鼠同源类型的投射在丘脑中都有较高的代表性，而丘脑是初级视觉皮层的供应来源。

总之，研究人员认为，侏儒RGC不是灵长类动物的创新，而是演化而来的古老类型的后代，随着灵长类动物演化，侏儒RGC的体积减少，数量增加，从而有助于提高视力灵敏度和增加皮层对视觉信息的处理。

附：英文原文

Title: Evolution of neuronal cell classes and types in the vertebrate retina

Author: Hahn, Joshua, Monavarfeshani, Aboozar, Qiao, Mu, Kao, Allison H., Klsch, Yvonne, Kumar, Ayush, Kunze, Vincent P., Rasys, Ashley M., Richardson, Rose, Wekselblatt, Joseph B., Baier, Herwig, Lucas, Robert J., Li, Wei, Meister, Markus, Trachtenberg, Joshua T., Yan, Wenjun, Peng, Yi-Rong, Sanes, Joshua R., Shekhar, Karthik

Issue&Volume: 2023-12-13

Abstract: The basic plan of the retina is conserved across vertebrates, yet species differ profoundly in their visual needs1. Retinal cell types may have evolved to accommodate these varied needs, but this has not been systematically studied. Here we generated and integrated single-cell transcriptomic atlases of the retina from 17 species: humans, two non-human primates, four rodents, three ungulates, opossum, ferret, tree shrew, a bird, a reptile, a teleost fish and a lamprey. We found high molecular conservation of the six retinal cell classes (photoreceptors, horizontal cells, bipolar cells, amacrine cells, retinal ganglion cells (RGCs) and Müller glia), with transcriptomic variation across species related to evolutionary distance. Major subclasses were also conserved, whereas variation among cell types within classes or subclasses was more pronounced. However, an integrative analysis revealed that numerous cell types are shared across species, based on conserved gene expression programmes that are likely to trace back to an early ancestral vertebrate. The degree of variation among cell types increased from the outer retina (photoreceptors) to the inner retina (RGCs), suggesting that evolution acts preferentially to shape the retinal output. Finally, we identified rodent orthologues of midget RGCs, which comprise more than 80% of RGCs in the human retina, subserve high-acuity vision, and were previously believed to be restricted to primates2. By contrast, the mouse orthologues have large receptive fields and comprise around 2% of mouse RGCs. Projections of both primate and mouse orthologous types are overrepresented in the thalamus, which supplies the primary visual cortex. We suggest that midget RGCs are not primate innovations, but are descendants of evolutionarily ancient types that decreased in size and increased in number as primates evolved, thereby facilitating high visual acuity and increased cortical processing of visual information.

DOI: 10.1038/s41586-023-06638-9

Source: https://www.nature.com/articles/s41586-023-06638-9

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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