Role of hindbrain in inner ear morphogenesis: Analysis of Noggin knockout mice

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2007.08.013 Byline: Jinwoong Bok (a), Lisa J. Brunet (b), Omar Howard (a), Quianna Burton (a), Doris K. Wu (a) Keywords: Noggin; BMP; Inner ear; Rhombomere; Hindbrain; Chondrogenesis Abstract: Signaling from rhombomeres 5 and 6 of the hindbrain is thought to be important for inner ear patterning. In Noggin -/- embryos, the gross anatomy of the inner ear is distorted and malformed, with cochlear duct outgrowth and coiling most affected. We attributed these defects to a caudal shift of the rhombomeres caused by the shortened body axis and the kink in the neural tube. To test the hypothesis that a caudal shift of the rhombomeres affects inner ear development, we surgically generated chicken embryos in which rhombomeres 5 and 6 were similarly shifted relative to the position of the inner ears, as in Noggin mutants. All chicken embryos with shifted rhombomeres showed defects in cochlear duct formation indicating that signaling from rhombomeres 5 and 6 is important for cochlear duct patterning in both chicken and mice. In addition, the size of the otic capsule is increased in Noggin -/- mutants, which most likely is due to unopposed BMP signaling for chondrogenesis in the peri-otic mesenchyme. Author Affiliation: (a) National Institute on Deafness and Other Communication Disorders, 5 Research Ct., Rm 2B34, Rockville, MD 20850, USA (b) Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA Article History: Received 15 August 2006; Revised 2 August 2007; Accepted 6 August 2007