A gradient of Bmp7 specifies the tonotopic axis in the developing inner ear.
The auditory systems of animals that perceive sounds in air are organized to separate sound stimuli into their component frequencies. Individual tones then stimulate mechanosensory hair cells located at different positions on an elongated frequency (tonotopic) axis. During development, immature hair cells located along the axis must determine their tonotopic position in order to generate frequency-specific characteristics. Expression profiling along the developing tonotopic axis of the chick basilar papilla (BP) identified a gradient of Bmp7. Disruption of that gradient in vitro or in ovo induces changes in hair cell morphologies consistent with a loss of tonotopic organization and the formation of an organ with uniform frequency characteristics. Further, the effects of Bmp7 in determination of positional identity are shown to be mediated through activation of the Mapk, Tak1. These results indicate that graded, Bmp7-dependent, activation of Tak1 signalling controls the determination of frequency-specific hair cell characteristics along the tonotopic axis.
Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 35A Convent Drive, Bethesda, Maryland 20892-3729, USA.
Zoë F
ZF
Mann
Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
Benjamin R
BR
Thiede
Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 35A Convent Drive, Bethesda, Maryland 20892-3729, USA.
Weise
W
Chang
Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
Jung-Bum
JB
Shin
Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 35A Convent Drive, Bethesda, Maryland 20892-3729, USA.
Helen L
HL
May-Simera
National Heart and Lung Institute, Imperial College, Guy Scadding Building, Dovehouse Street, London SW3 6LY, UK.
Michael
M
Lovett
Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
Jeffrey T
JT
Corwin
Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 35A Convent Drive, Bethesda, Maryland 20892-3729, USA.
Matthew W
MW
Kelley
D000818:Animals; D055419:Bone Morphogenetic Protein 7 / Q000235:genetics* / Q000378:metabolism; D002642:Chick Embryo; D007758:Ear, Inner / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006198:Hair Cells, Auditory / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000235:genetics* / Q000378:metabolism; D009925:Organ of Corti / Q000196:embryology / Q000378:metabolism*; D038081:Organogenesis / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism*; D015398:Signal Transduction; D000099151:MAP Kinase Kinase Kinase 7
D055419:Bone Morphogenetic Protein 7; D020930:MAP Kinase Kinase Kinases; D012333:RNA, Messenger; D000099151:MAP Kinase Kinase Kinase 7