The same genes could hold the key to regenerating cells in the ear and eye, according to a new mouse study from the USC Stem Cell laboratory of Ksenia Gnedeva, Ph.D. Researchers focused on a group of interacting genes called the Hippo pathway, which serve as a “stop growing” signal that the lab has shown to inhibit cell proliferation in the ear during embryonic development. The scientists demonstrated that the Hippo pathway also suppresses the regeneration of damaged sensory receptors in the ear and eye of adult mice. Researchers applied an experimental compound developed by the lab to inhibit a key protein in the Hippo pathway known as Lats1/2 and found that progenitor cells known as supporting cells responded by proliferating in the utricle, which is a sensory organ in the inner ear that helps with balance. However, the same cells did not respond in the organ of Corti, which is the hearing sensory organ. The scientists then identified a gene encoding a protein called p27^Kip1 which was blocking this step towards sensory cell regeneration in the organ of Corti and discovered this inhibitory protein was also high in the retina. They created a transgenic mouse in which the level of p27^Kip1 could be reduced in the inner ear and the retina and found that inhibiting the Hippo pathway in these mice effectively caused supporting cells to proliferate in the organ of Corti. In the retina, inhibiting the Hippo pathway induced the proliferation of progenitor cells known as Müller glia. Surprisingly, the researchers discovered that some of the Müller glia progeny, without further manipulation, converted to sensory photoreceptors and other neuronal cell types in the retina.