1152 Ephrin-B Reverse Signaling for Palatal EMT Requires Contact

Friday, March 23, 2012: 3:30 p.m. - 4:45 p.m.
Presentation Type: Poster Session
M. GREWAL, S. WOJCIECHOWSKI, F. MOHAMED, A. SACHAR, M.J. SERRANO, M.D. BENSON, and K. SVOBODA, Biomedical Sciences, Baylor College of Dentistry, Dallas, TX
Objective: We previously demonstrated that ephrin-B reverse signaling is necessary and sufficient to cause palate EMT and fusion when palatal shelves were cultured with their medial edge epithelia (MEE) in contact.  Furthermore, this signaling was PI-3 kinase dependent.  Palatal shelves depend on a contact with apposing shelf MEE to initiate fusion.  Since Ephs and ephrins are membrane-bound molecules that control contact-mediated events in development, we asked whether they supply the contact-dependent fusion initiation signal.

Method: Embryonic day eight (E8) chicken palatal shelves were cultured on nucleopore polycarbonate membranes in isolation from each other for 24, 48, or 72 h in 37oC with 5% CO2.  Medium was replaced every 24 h with fresh TGFß3 (50 ng/ml), clustered EphB2/Fc (4 µg/ml), or control IgG Fc (also 4 µg/ml).  TGFß3 or EphB2/Fc at these concentrations normally cause complete fusion within 72 h when shelves are in contact.

Result: We predicted that clustered (bioactive) Eph/B2/Fc would cause EMT and epithelial seem degradation even in the absence of shelf-to-shelf MEE contact.  Instead, we observed an unusual hypertrophy of the epithelial layer.  The cells in this layer lacked the polarity and organization of a normal epithelium, but neither did they display the fibroblastic morphology of the underlying mesenchyme.

Conclusion: Application of clustered, soluble EphB2/Fc is not sufficient to cause palatal EMT and epithelial layer degradation without shelf-shelf contact.  Instead, ephrin signaling in the absence of the contact-mediated signal appears to initiate a growth/proliferation program in the epithelium.  We are currently characterizing the consequences of this signaling and its underlying mechanism.

Supported by Baylor Oral Health Foundation

This abstract is based on research that was funded entirely or partially by an outside source: Baylor Oral Health Foundation

Keywords: Cleft lip-palate, Embryology, Ephrins, Growth & development and Tissue or organ culture
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