Starving for more: Nutrient sensing by LIN-28 in adult intestinal progenitor cells.

In this Extra View, we extend our recent work on the protein LIN-28 and its role in adult stem cell divisions. LIN-28 is an mRNA- and microRNA-binding protein that is conserved from worms to humans. When expressed ectopically, it promotes the reprogramming of differentiated vertebrate cells into pluripotent stem cells as well as the regeneration of vertebrate tissues after injury. However, its endogenous function in stem cell populations is less clear. We recently reported that LIN-28 is specifically expressed in progenitor cells in the adult Drosophila intestine and enhances insulin signaling within this population. Loss of lin-28 alters the division patterns of these progenitor cells, limiting the growth of the intestinal epithelium that is ordinarily caused by feeding. Thus, LIN-28 is part of an uncharacterized circuit used to remodel a tissue in response to environmental cues like nutrition. Here, we extend this analysis by reporting that the levels of LIN-28 in progenitor cells are sensitive to nutrient availability. In addition, we speculate about the role of LIN-28 in the translational control of target mRNAs such as Insulin Receptor (InR) and how such translational control may be an important mechanism that underlies the stem cell dynamics needed for tissue homeostasis and growth.