Fate trafficking

Asymmetric cell fates can be defined by creating an endocytic compartment in one incipient daughter but not the other, say Gregory Emery, Juergen Knoblich (IMB, Vienna, Austria), and colleagues. Only the daughter with a functioning recycling endosome can direct Delta back to the plasma membrane so that it can activate Notch on the other daughter.

Knoblich studies fly sensory organ precursor (SOP) cells, which divide to form two cells—pIIa and pIIb—with different fates. Those fates are decided largely by Notch and its binding partner Delta. In pIIb, the asymmetry determinants Numb and Neuralized turn off Notch and increase the endocytosis that somehow activates Delta activity.

The Austrian team found that only in pIIb did Delta travel to a compartment resembling a recycling endosome. From here it could be sent back to...