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.
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.
Simonneau
Lionel
L
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
Gallego
Mireille
M
Pujol
Remy
R
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
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