Cooper & Milinkovitch shows that intravenous injection of Sonidegib, a potent SHH pathway inhibitor, on embryonic day 9 (E9), temporarily generates a striped domain of skin SHH expression, halting morphogenesis and lies in unclogged plumage buds – eng feathers in to proto feathers in to proto feathers. Image credits: Fabrice Berger & Michel Milinkovitch.
Bird feathers are complex appendages that vary widely in morphology between boys and adults, in species and body regions.
Understanding both the developmental and evolutionary mechanisms that underpin this morphological diversity has long fascinated biologists.
The morphological complexity of bird feathers makes them an ideal model for investigating embryonic patterning.
In particular, the SHH pathway is an important mediator of feather growth and divergence.
However, it is functional in vivo Evidence regarding its role during feather development remains limited.
To bridge this knowledge gap, University of Geneva researchers Rory Cooper and Michel Millinkovich studied the normal patterning of embryo wings and their shape development using light sheet fluorescence microscopy imaging.
They also pharmacologically inhibited SHH pathway signaling during embryo developmental wing development prior to wing feather development using Sonidegib’s precise intravenous injection.
This treatment temporarily corrected SHH expression to generate striped domains instead of skin spots, temporarily halted feather development, and resulted in non-branched, nonabsorbable feather buds that resemble unpredicted primitive feathers until day 14.
Feather development partially recovered during development, but hatched Sonidegib treated chickens showed naked areas on the skin surface with perturbed follicles.
Surprisingly, these follicles were subsequently re-activated by 7 weeks after hatching, highlighting the robustness of the feather pattern as a developmental process.
Overall, this study provides comprehensive functional evidence for the role of the SHH pathway in mediating chicken feather development, supporting the idea that modified SHH signaling contributes to the evolutionary diversification of other skin appendages, such as feather and foot measures.
This study also shows the importance of in vivo Experiments to gain a comprehensive understanding of developmental systems.
“Because the SHH pathway plays an important role in feather development, we wanted to observe what happens when it is blocked,” Dr. Cooper said.
“We observed the formation of non-branched, non-absorbable buds similar to the putative early stages of protofeathers by injecting molecules that block the SHH signaling pathway just before fetal buds appeared on the wings.”
“However, from day 14 of embryonic development, feather morphogenesis has partially resolved.”
“In addition, although the chicks were hatched with patches of naked skin, the dormant subcutaneous follicles were autonomously re-activated, eventually producing chickens with normal feathers.”
“Our experiments show that temporary disruptions in footscale development can be permanently transformed into feathers, but it is much more difficult to permanently disrupt feather development itself,” added Dr. Mirinkovich.
“Obviously, over the course of evolution, the network of interacting genes has become very robust and ensures proper development even under substantial genetic or environmental perturbations.”
“The big challenge right now is how genetic interactions evolve to allow for the emergence of morphological novelty, such as primitive wings.”
study It was published online today in the journal PLOS Biology.
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RL Cooper & MC Milinkovitch. 2025. in vivo Antagonism of the Sonic Hedgehog pathway temporarily results in atom-like structures of chicken ancestors. Plos Biol 23(3): E3003061; doi: 10.1371/journal.pbio.3003061
Source: www.sci.news
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