Adult brain neurons are actively maintained in a postmitotic state by the cyclin-dependent kinase inhibitors (CKIs) p19Ink4d (Ink4d) and p27Kip1 (Kip1). However, the roles of these CKIs in other terminally differentiated populations, such as the organ of Corti — the auditory sensory epithelium of mammals — have been unclear. In the April 28 Nature Cell Biology, Ping Chen and colleagues from the House Ear Institute, Los Angeles, show that mice lacking the CKI Ink4d display progressive hearing loss (Nature Cell Biology, DOI:10.1038/ncb976, April 28, 2003).

Chen et al. observed that targeted deletion of Ink4d alone is sufficient to disrupt the maintenance of the postmitotic state of sensory hair cells in postnatal mice. They showed that in Ink4d−/− animals, hair cells aberrantly re-entered the cell cycle and subsequently underwent apoptosis, resulting in progressive hearing loss.

This is "a novel mechanism underlying a non-syndromic form of progressive hearing...

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