ASYMMETRIC EXPRESSION OF NOTCH DELTA/SERRATE IS ASSOCIATED WITH THE ANTERIOR-POSTERIOR AXIS OF FEATHER BUDS/

We studied the roles of Notch, Delta, and Serrate in vertebrate epithe lial appendage morphogenesis using feather as a model and found the fo llowing. (1) C-Notch-1, C-Delta-1, and C-Serrate-1 are not expressed a t the early placode stage and are therefore not involved in the determ ination of bud versus interbud compartments. (2) From symmetric short buds to asymmetric long buds, C-Delta-1 and C-Serrate-1 are expressed in the posterior bud mesenchyme in a nested fashion, while C-Notch-l i s expressed as a stripe perpendicular to the anterior-posterior (A-P) axis and positioned posterior to the midpoint. (3) Epithelial-mesenchy mal recombination with rotation led to the disappearance of these gene s followed by their reappearance with new positions appearing to predi ct their new morphological orientation. (4) Conditions leading to bran ched buds (e.g., recombination of later buds) show polarized staining patterns before branching occurs. (5) Conditions leading to symmetrica l round buds (e.g., treated with the protein kinase A agonist forskoli n) suppress expression of all three genes. These results lead us to hy pothesize that Notch, Delta, and Serrate are involved in establishing the A-P asymmetry of feather buds. (C) 1997 Academic Press.