Consensus.aiによるまとめ。

Introduction

The transplantation of the node, a critical embryonic structure, has been studied for its ability to induce ectopic body axes in both mice and chicks. This research explores the node’s role in axis formation and its potential to organize and pattern embryonic development when transplanted to non-native locations.

Key Insights

• Induction of Ectopic Neural Axis in Mice:
  • Transplanting the mouse node to a posterolateral location in a host embryo induces a second neural axis and ectopic somites. The graft predominantly forms notochord and endoderm, while the host contributes to neurectoderm and somites.
• Induction of Ectopic Axis in Chicks:
  • Hensen’s node in chick embryos can induce a complete embryonic axis, including a fully patterned central nervous system, when transplanted to an ectopic site. This includes host-derived neural tissue.
• Role of Node in Axis Formation:
  • The mouse node is crucial for the formation of the notochord, floor plate, and gut endoderm. Its ablation leads to the recruitment of surrounding tissues to restore the neural tube and paraxial mesoderm, although the body axis may be foreshortened and somite formation delayed.
• Synergistic Activity in Axis Induction:
  • In mice, the combination of the early gastrula organizer (posterior epiblast), anterior visceral endoderm, and anterior epiblast is necessary to induce anterior neural structures and form an ectopic axis. The anterior germ layer tissues alone do not act as a classical organizer5.
• Molecular Mechanisms in Chicks:
  • The protein Tsukushi (TSK) in chicks inhibits BMP signaling, which is essential for the formation of Hensen’s node and the induction of an ectopic node when combined with the middle primitive streak7.

Conclusion

The transplantation of the node in both mice and chicks can induce the formation of ectopic body axes, demonstrating its critical role in embryonic patterning. In mice, the node primarily contributes to the notochord and endoderm, while（全然対比になっていない。。） in chicks, Hensen’s node can induce a complete axis including neural tissues. The induction of anterior neural structures in mice requires a combination of specific germ layer tissues, highlighting the complexity of axis formation. Molecular mechanisms, such as BMP inhibition by Tsukushi in chicks, further elucidate the processes involved in node-induced axis formation.