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キーワード:
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要旨:
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 m 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.
