Expression of Delta1 and Serrate1 (Jagged1) in the mouse inner ear

The Notch signalling pathway is thought to play a key part in controlling t he production of sensory hair cells in the vertebrate inner ear via lateral inhibition; but there is disagreement as to which Notch ligands are expres sed in hair cells as they develop. We show, using a mouse Delta1:LacZ knock -in as a reporter, that nascent hair cells, but nut their neighbours, expre ss Delta1. Expression of Serrate1 (Jagged1). meanwhile becomes restricted t o the supporting cells of each sensory patch. Delta is also expressed: (a) at early stages, at the site of otic neurogenesis; and (b) in scattered cel ls of the endolymphatic sac, as is Serrate1. (C) 1999 Elsevier Science Irel and Ltd. All rights reserved.