Surprisingly, newborn mice have a limited ability to regenerate hair cells, although this capability disappears within the first few weeks of life. Because of this transition, we can address experimentally the failure of hair cell regeneration in mammals. Our project is investigating changes in the genetic material, the chromatin, that are responsible for orchestrating the differentiation of new hair cells within the newborn organ of Corti in the inner ear and the changes in the chromatin that lead to the failure of regeneration in the adult mammalian inner ear. This year we will focus on changes to the chromatin that occur after the loss of hair cell function and will test methods for activating hair cell regeneration by direct modification of the chromatin.