Developmental gene expression profiling along the tonotopic axis of the mouse cochlea.
The mammalian cochlear duct is tonotopically organized such that the basal cochlea is tuned to high frequency sounds and the apical cochlea to low frequency sounds. In an effort to understand how this tonotopic organization is established, we searched for genes that are differentially expressed along the tonotopic axis during neonatal development. Cochlear tissues dissected from P0 and P8 mice were divided into three equal pieces, representing the base, middle and apex, and gene expression profiles were determined using the microarray technique. The gene expression profiles were grouped according to changes in expression levels along the tonotopic axis as well as changes during neonatal development. The classified groups were further analyzed by functional annotation clustering analysis to determine whether genes associated with specific biological function or processes are particularly enriched in each group. These analyses identified several candidate genes that may be involved in cochlear development and acquisition of tonotopy. We examined the expression domains for a few candidate genes in the developing mouse cochlea. Tnc (tenacin C) and Nov (nephroblastoma overexpressed gene) are expressed in the basilar membrane, with increased expression toward the apex, which may contribute to graded changes in the structure of the basilar membrane along the tonotopic axis. In addition, Fst (Follistatin), an antagonist of TGF-β/BMP signaling, is expressed in the lesser epithelial ridge and at gradually higher levels towards the apex. The graded expression pattern of Fst is established at the time of cochlear specification and maintained throughout embryonic and postnatal development, suggesting its possible role in the organization of tonotopy. Our data will provide a good resource for investigating the developmental mechanisms of the mammalian cochlea including the acquisition of tonotopy.
Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Korea. bokj@yuhs.ac
Eun Jin
EJ
Son
Ling
L
Wu
Heejei
H
Yoon
Sunhee
S
Kim
Jae Young
JY
Choi
Jinwoong
J
Bok
D000818:Animals; D000831:Animals, Newborn; D001307:Auditory Perception / Q000235:genetics*; D002454:Cell Differentiation; D016000:Cluster Analysis; D003051:Cochlea / Q000166:cytology / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism*; D047108:Embryonic Development / Q000235:genetics; D038681:Follistatin / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D006198:Hair Cells, Auditory / Q000166:cytology / Q000378:metabolism; D017403:In Situ Hybridization; D051379:Mice; D058977:Molecular Sequence Annotation; D055514:Nephroblastoma Overexpressed Protein / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
C526320:Ccn3 protein, mouse; D038681:Follistatin; D055514:Nephroblastoma Overexpressed Protein