The oenocytes went 3 by 3

A specialized cell type in flies leaves its specifying hub in groups of 3 cells, according to Véronique Brodu, Philip Elstob, and Alex (NIMR, Mill Hill, London, UK). Each group gets stimulation of its EGF receptor (EGFR) in a controlled pulse, which may ensure reliable differentiation.

Gould studies oenocytes—a large, secretory cell type in flies that may generate or respond to hormone signals during embryonic moults. Looking at oenocyte specification in real time, Gould's group noticed that cells clustered around a C1 cell—the source of EGFR ligand—in groups of 3, and departed in the same cohorts. Normal animals went through two such pulses of 3 cells arriving and leaving, although overexpression of an EGFR ligand resulted in up to 7 or 8 pulses.

Several downstream targets of EGFR signaling were expressed in...