Vertebrate skin appendage early development is mediated by conserved molecular signalling composing a dynamical reaction-diffusion-like system. Variations to such systems contribute to the remarkable diversity of skin appendage forms within and among species. Here, we demonstrate that stage-specific transient agonism of sonic hedgehog (Shh) pathway signalling in chicken triggers a complete and permanent transition from reticulate scales to feathers on the ventral surfaces of the foot and digits. Resulting ectopic feathers are developmentally comparable to feathers adorning the body, with down-type feathers transitioning into regenerative, bilaterally symmetric contour feathers in adult chickens. Crucially, this spectacular transition of skin appendage fate (from nodular reticulate scales to bona-fide adult feathers) does not require sustained treatment. Our RNA-sequencing analyses confirm that SAG treatment specifically promotes the expression of key Shh pathway-associated genes. These results indicate that variations in Shh pathway signalling likely contribute to the natural diversity and regionalisation of avian integumentary appendages.

Chicken embryos were injected with either SAG or DMSO as a control at embryonic day 11 (E11). Digits from samples were then dissected at E11+5 hours, E12, E14 and E16. By E16, abundant ectopic feather buds are observed, resulting from SAG treatment. Furthermore, both ventral and dorsal tissue was dissected separately from additional samples at E16, as the strongest SAG effect is observable on the ventral digit surface. Tissue samples were stored in Trizol, prior to RNA extraction, library preparation and Illumina sequencing. This dataset contains the raw sequencing reads. Please see the supplementary information of the published article to download the aligned reads, and see the methods section for further details regarding both experimentation and sequencing of these samples.  

Any RNA-sequencing alignment and analysis software can be used to open these data files, including both R and CLC Genomics Workbench.