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. Author manuscript; available in PMC: 2020 Nov 27.
Published in final edited form as: Cell. 2019 Nov 27;179(6):1409–1423.e17. doi: 10.1016/j.cell.2019.11.008

Figure 3. Molecular Pathways Regulating Cortex and Medulla Organization during Rachis Development.

Figure 3.

(A) Internal structure and keratin expression in developing chicken flight feather rachides. Increasing maturity, bottom. First column, H&E staining. Second to fourth columns, K75, chr25-FK12, and K13A in situ hybridization. Red, green, and blue arrows indicate the expression of K75, chr25-FK12, and K13A, respectively.

(B–C′) Comparison of chicken (B and B′) and mallard duck (C and C′) rachis development. (B and C) Immunostaining of β-cat, K17, and desmoglein 1 (DSG1). Samples are pseudocolored red (β-cat) and purple (K17) using Photoshop. DSG1 stained images kept the original green color. (B′ and C′) Schematic drawings of different rachis architectures.

(D) Functional test of BMP and TGF-β pathways with RCAS-BMP4 and RCAS-Ski perturb rachis morphology. White arrows indicate reduced medulla cells. Green arrows indicate disrupted feather keratin expression. Levels evaluated are similar to (A) (bottom level). chr25-FK12, chromosome 25-feather keratin 12; dc, dorsal cortex; DSG1, desmoglein 1; K13A, keratin 13A; K75, keratin 75; m, medulla; RCAS, replication competent avian sarcoma virus; vc, ventral cortex.

See also Figure S4.