McHedlishvili Levan, Epperlein Hans H, Telzerow Anja, Tanaka Elly M
Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307 Dresden, Germany.
Development. 2007 Jun;134(11):2083-93. doi: 10.1242/dev.02852.
Complete regeneration of the spinal cord occurs after tail regeneration in urodele amphibians such as the axolotl. Little is known about how neural progenitor cells are recruited from the mature tail, how they populate the regenerating spinal cord, and whether the neural progenitor cells are multipotent. To address these issues we used three types of cell fate mapping. By grafting green fluorescent protein-positive (GFP(+)) spinal cord we show that a 500 microm region adjacent to the amputation plane generates the neural progenitors for regeneration. We further tracked single nuclear-GFP-labeled cells as they proliferated during regeneration, observing their spatial distribution, and ultimately their expression of the progenitor markers PAX7 and PAX6. Most progenitors generate descendents that expand along the anterior/posterior (A/P) axis, but remain close to the dorsal/ventral (D/V) location of the parent. A minority of clones spanned multiple D/V domains, taking up differing molecular identities, indicating that cells can execute multipotency in vivo. In parallel experiments, bulk labeling of dorsally or ventrally restricted progenitor cells revealed that ventral cells at the distal end of the regenerating spinal cord switch to dorsal cell fates. Analysis of PAX7 and PAX6 expression along the regenerating spinal cord indicated that these markers are expressed in dorsal and lateral domains all along the spinal cord except at the distal terminus. These results suggest that neural progenitor identity is destabilized or altered in the terminal vesicle region, from which clear migration of cells into the surrounding blastema is also observed.
在蝾螈等有尾两栖动物的尾巴再生后，脊髓会完全再生。关于神经祖细胞如何从成熟尾巴中募集、如何在再生脊髓中聚集以及神经祖细胞是否具有多能性，人们了解甚少。为了解决这些问题，我们使用了三种细胞命运图谱方法。通过移植绿色荧光蛋白阳性（GFP(+)）脊髓，我们发现截肢平面附近500微米的区域产生了用于再生的神经祖细胞。我们进一步追踪了单核GFP标记的细胞在再生过程中的增殖情况，观察它们的空间分布，以及最终它们对祖细胞标志物PAX7和PAX6的表达。大多数祖细胞产生的后代沿着前后（A/P）轴扩展，但仍靠近亲代细胞的背腹（D/V）位置。少数克隆跨越多个D/V区域，具有不同的分子特征，表明细胞在体内可以执行多能性。在平行实验中，对背侧或腹侧受限祖细胞进行整体标记显示，再生脊髓远端的腹侧细胞会转变为背侧细胞命运。对再生脊髓中PAX7和PAX6表达的分析表明，除了在远端末端外，这些标志物在整个脊髓的背侧和外侧区域均有表达。这些结果表明，神经祖细胞的身份在终末泡区域不稳定或发生改变，在该区域还观察到细胞明显迁移到周围的芽基中。
