Investigation of feather follicle morphogenesis and the expression of the Wnt/β-catenin signaling pathway in yellow-feathered broiler chick embryos

1. This study investigated the pattern of feather follicle morphogenesis and the expression of the Wnt/β-catenin signalling pathway in the skin of yellow-feathered broiler chick embryos during feather development, using haematoxylin and eosin (H&E) staining and Western blot assays, respectively. 2. The results showed that the skin displayed protrusions during embryonic days E7-E9, feather buds elongated during E10-E11 with anterior-posterior and proximal-distal asymmetries, and the epidermis invaginated to form the primary feather follicles (Pfs) at E12. At E13, the formation of the feather follicle and the epidermis at the base of the feather bud further invaginated into the dermis. By E15, Pf formation was essentially complete, and secondary feather follicles (Sfs) appeared. It was speculated that Pfs and Sfs developed independently and that Pfs occurred earlier than Sfs. 3. Quantitative measurements of Pf density reached a maximum at E15 and then decreased gradually. Sf density started to increase from E15. 4. Protein expression levels of β-catenin, TCF4, cyclin D1, and c-Myc were significantly increased during E8-E12 (P < 0.05) and then decreased from E13 to the day of hatching (DOH) (P < 0.05). The result of the β-catenin immunolocalisation signal intensity assay was consistent with the result of the Western blot assay. 5. Collectively, the results indicated that the Wnt/β-catenin signalling pathway is essential for promoting the development of feather follicles, especially during E7-E15.