Patterned by adhesion

Elaborate tissue patterns are formed by two cell types with complementary adhesion molecules, as revealed by Sujin Bao and Ross Cagan (Washington University, St. Louis, MO). Favored heterophilic attractions between the two adhesion molecules, they show, pattern the fly eye.

Patterning has often taken a back seat to fate determination in cell biology studies. “We've spent buckets of time,” says Cagan, “finding all sorts of signaling molecules that explain cell fate, but not patterning. We can make kidney cells [in vitro], but how do you sort them into a glomerulus? What we really want to know is not what makes a lung cell, but what makes a lung.”

A hint came when others found that mutation of the Ig family member Roughest caused disorganized ommatidia in flies but did not affect cell...