Bmi1 represses Ink4a/Arf and Hox genes to regulate stem cells in the rodent incisor

The polycomb protein BMI1 has been linked to maintenance of adult stem cells. Klein and colleagues find that BMI1 is also required for the maintenance of stem cells in the continuously growing mouse incisor, through repression of the Ink4a/Arf locus to modulate the proliferation of stem cells and repression of Hox genes to prevent inappropriate lineage decisions in stem cell progeny.