Cells read their environment to trigger an appropriate response for tissue homeostasis. Work now shows that intestinal progenitor cells use the RNA-binding protein Lin-28 to detect such a change and trigger insulin signaling as well as promote symmetric cell division to make full use of increased nutrient availability. Progenitor cells in the embryo and adult maintain their cell number by symmetric division but also generate specific cell types through asymmetric division. Lin-28 functions in early development to ramp up cell number, but an adult role is less clear. Work by Chen et al. identifies Lin-28 in the fly adult intestine as a factor controlling adult stem cell division, and it does so via the insulin-like receptor InR and independently of its well-known target Let-7.
