Spatiotemporal reconstruction of axolotl brain development and regeneration at single-nuclei resolution

Brain regeneration upon injury requires a precise coordination of complex cellular and molecular responses in a time- and region-specific manner. Identifying key types of cells directing specific brain regeneration processes and underlying mechanisms hold great promise for the advance of regenerative medicine. However, progress in the field has been hampered largely due to lack of injury recovery capacity of mammal brain models and appropriate tools to comprehensively dissect the regeneration process at molecular level. Here, using the brain injury model of axolotl that can almost fully regenerate the injured tissue, and the high-resolution Stereo-seq (Spatio-Temporal Enhanced REsolution Omics-sequencing), we present the first in situ transcriptomic atlas at single-nuclei resolution that enables spatial characterization of cells combined with global gene expression information throughout brain development and regeneration. Excitingly, we discovered a marked heterogeneity of radial glial cell (RGC) types with distinct behaviors. Particularly, one subtype of RGCs is immediately activated at early stages of telencephalon regeneration and start to proliferate while other RGCs remain dormant. Such RGC subtype appears to be the major cell type gradually covering the injured area before potentially transformed into the lost neurons of exactly the same cellular identity. Altogether, our study provides a systematic dissection of the molecular events underlying neural cell plasticity in the amphibian brain, laying the foundation for further mechanistic studies in this and other species.

损伤后的脑再生需要复杂细胞和分子反应在时间与区域特异性层面的精确协调。识别指导特定脑再生过程的关键细胞类型及其潜在机制，对再生医学的发展具有重要意义。然而，该领域的进展在很大程度上受到阻碍——一方面是哺乳动物脑模型缺乏损伤恢复能力，另一方面是缺乏能在分子水平全面解析再生过程的合适工具。在此，我们利用可近乎完全再生受损组织的美西螈（axolotl）脑损伤模型，结合高分辨率的Stereo-seq（时空增强分辨率组学测序，Spatio-Temporal Enhanced REsolution Omics-sequencing）技术，首次构建了单细胞核分辨率的原位转录组图谱，该图谱可在脑发育与再生全过程中，将细胞的空间特征与全局基因表达信息相结合。令人兴奋的是，我们发现放射状胶质细胞（radial glial cell, RGC）类型存在显著异质性，且各亚型行为特征截然不同。特别地，在端脑再生早期，一种RGC亚型会立即被激活并开始增殖，而其他亚型则保持休眠状态。这种激活的RGC亚型似乎是逐渐覆盖损伤区域的主要细胞类型，随后可能转化为具有完全相同细胞身份的丢失神经元。总之，本研究系统解析了两栖动物脑内神经细胞可塑性背后的分子事件，为该物种及其他物种的进一步机制研究奠定了基础。