FOCAL POINT  (Left to right) Mateusz Trylinski, Lydie Couturier, Khallil Mazouni, François Schweisguth, and (not pictured) Léa Darnet reveal that the endocytic regulator Numb down-regulates Notch signaling by sorting the Notch receptor and its binding partner Sanpodo to late endosomes/lysosomes during Drosophila sensory bristle morphogenesis. The researchers uncovered this pathway by dual tagging Notch and Sanpodo with both green and red fluorescent proteins after realizing that individually tagged Notch-GFP (middle) and Notch-mCherry (right) showed different fluorescence patterns representing two distinct populations of the Notch receptor. This dual-tagging approach could be useful for following the endocytic sorting of many other membrane proteins.

PHOTO COURTESY OF STEPHANIE PONTIER