Principles of developmental signaling

Question 1

Explain the Notch/Delta signaling pathway.

Answer 1

• Delta ligand binds to Notch in the receiving cell
• Endocytosis of Delta by the signaling cell stretches Notch extracellular domain, exposing cryptic binding sites, such that Notch is cleaved by some protease that recognize the cryptic binding sites at its extracellular domain
• The cleaved extracellular domain remains bound to Delta is internalized by the signaling cell and is degraded in lysosomes
• Protease cleaves Notch, releasing the Notch intracellular domain
• Notch intracellular domain moves to the nucleus where it interacts with transcription factors, and regulate gene expression

Question 2

In neuronal and epidermal cells, is the notch signaling pathway on or off, respectively?

Answer 2

Neuronal - off
Epidermal - on