Theory 24/Organelle contacts/Correlative microscopy
Contacts Are the Functional Unit
The claim
Whether an organelle contact site signals is set by the ratio of membrane apposition to diffusion distance, so a contact that looks structural may be functionally silent.
01Mechanism
Signalling requires molecules to cross the gap; the ratio determines whether the contact is close enough to matter.
02Prediction
Signalling should occur only below a gap threshold.
03Refutation
Signalling independent of gap distance would remove the apposition argument.
04What makes it checkable
Correlative light and electron microscopy now measures the gap at identified contacts, which light microscopy could only suggest.
05Why it was not testable before
Diffraction-limited imaging could not resolve the gap.