Theory 20/Developmental self-organisation/Organoids
Pattern Needs a Size Window
The claim
An organoid self-organises into patterned tissue only within a window of the ratio of its size to the length scale of its signalling, so too small and too large both fail.
01Mechanism
Morphogen gradients set pattern; the tissue must be large enough to resolve a gradient but small enough to be supplied by diffusion.
02Prediction
Patterning should appear only within a size window.
03Refutation
Patterning across all sizes would remove the gradient argument.
04What makes it checkable
Organoids now allow the same genetic programme to be observed at controlled sizes, which embryos could not provide.
05Why it was not testable before
Human development could not be manipulated experimentally; organoids made size a variable.