The Drosophila intestine is known to undergo adaptive growth in response to feeding, and this growth is fuelled by the symmetric self-renewing divisions of intestinal stem cells (ISCs). But what controls ISC division patterns? Here, on p. , Nicholas Sokol and colleagues reveal that the RNA-binding protein Lin-28 promotes symmetric ISC divisions and hence tissue growth in the Drosophila intestine. They first show that Lin-28 is highly enriched in adult Drosophila ISCs. They further report that, although lin-28 null mutants are viable, adult mutant animals exhibit reduced numbers of ISCs. Following on from this, the researchers demonstrate that Lin-28 is required in ISCs to promote food-triggered self-renewing divisions and expansion of the ISC pool. Finally, they report that Lin-28 acts independently of its well-known target let-7 and instead interacts with mRNA encoding the insulin-like receptor (InR), suggesting that Lin-28 modulates InR levels, and thus insulin signalling, to control cell division patterns. In summary, the authors propose that Lin-28 acts as a stem cell intrinsic factor that boosts insulin signalling in ISCs and promotes their symmetric division in response to nutrients.
