title: Comparative expression patterns of T-, N-, E-cadherins, beta-catenin, and polysialic acid neural cell adhesion molecule in rat cochlea during development: implications for the nature of Kölliker's organ.
abstract: We investigated the expression patterns of several cell adhesion molecules (CAMs) during rat cochlea ontogeny, from embryo day 16 to adulthood, with the use of immunohistochemistry: neural cadherin (N-cad) and polysialic acid neural CAM (PSA-NCAM) as two different neural CAM paradigms; epithelial cadherin (E-cad), which was restricted to the epitheloid phenotype; and the cytoplasmic domain-free truncated-cadherin (T-cad). We made the following observations. (1) T-cad was present in all types of fibrocyte and in subdomains within the pillar cells. (2) E- and N-cad were expressed with mutually exclusive patterns and did not overlap with T-cad. All cochlear epithelial cells, including the sensory outer hair cells (OHCs), were E-cad-positive, except for the negative inner hair cells (IHCs) and the nonsensory Kölliker's organ domain close to the IHCs. N-cad expression appeared first in the developing IHCs and then in the neighboring Kölliker's organ in an increasingly mediolateral gradient in opposition to the E-cad gradient. The OHCs, which are never N-cad positive, intensively expressed E-cad, as did the Hensen cells at the beginning of their differentiation. (3) The cadherin-linked molecule beta-catenin, absent in fibrocytes, was detected in all epithelial cell membranes and was prominent in the E-cad-rich modiolar extremity of Kölliker's organ. (4) Gradual PSA-NCAM expression was observed in the lateral portion of Kölliker's organ, and the intense PSA-NCAM expression was seen surrounding the IHCs. As development proceeded, PSA-NCAM immunoreactivity progressively became restricted to the basal poles of the IHCs, where it remained in the adult rat cochlea, suggesting a synaptic plasticity. Synaptic plasticity in rat cochlea and hypotheses about T-cad functions and neosensory features of the Kölliker's organ are discussed.
authors.affiliation: Laboratoire de Neurobiologie de l'Audition-Plasticité Synaptique, Institut National de la Santé et de la Recherche Médicale U254, Université Montpellier I, 34090 Montpellier, France. simoneau@montp.inserm.fr
authors.forename: Lionel
authors.initials: L
authors.lastname: Simonneau
authors.forename: Mireille
authors.initials: M
authors.lastname: Gallego
authors.forename: Remy
authors.initials: R
authors.lastname: Pujol
mesh_terms: D000818:Animals; D015820:Cadherins / Q000032:analysis / Q000096:biosynthesis*; D003051:Cochlea / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000096:biosynthesis*; D005786:Gene Expression Regulation / Q000502:physiology; D051379:Mice; D039842:Neural Cell Adhesion Molecule L1 / Q000032:analysis / Q000096:biosynthesis*; D009925:Organ of Corti / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012794:Sialic Acids / Q000032:analysis / Q000096:biosynthesis*; D015534:Trans-Activators / Q000032:analysis / Q000096:biosynthesis*; D051176:beta Catenin
chemical_list: C495267:CTNNB1 protein, mouse; D015820:Cadherins; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; C099972:H-cadherin; D039842:Neural Cell Adhesion Molecule L1; D012794:Sialic Acids; D015534:Trans-Activators; D051176:beta Catenin; C103469:polysialyl neural cell adhesion molecule