EXPRESSION AND REGULATION OF CEK-8 A CELL-TO-CELL SIGNALING RECEPTOR IN DEVELOPING CHICK LIMB BUDS

The Eph-related receptor tyrosine kinase gene, Cek-8, is expressed in mesenchyme at the tip of chick limb buds, with high levels of transcri pts posteriorly and apically but fading out anteriorly, Expression of Cek-8 in distal mesenchyme is regulated by apical ridge- and FGF-polar ising signals and retinoic acid, and is uniform across the anteroposte rior axis in talpid(3) mutants, These data indicate that Cek-8 express ion responds to regulatory signals during limb patterning and suggest that this receptor tyrosine kinase may have a role in coordinating res ponses to signals in the progress zone of early buds. Later on in limb development, Cek-8 expression is associated with cell condensations t hat form tendons and their attachments to cartilage rudiments and then in developing feather buds.