Regulatory Differences in Natal Down Development between Altricial Zebra Finch and Precocial Chicken

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Genomics

Background:

• Birds exhibit diverse hatchling development, classified as altricial (naked) or precocial (down-covered).
• The molecular mechanisms underlying this divergence in natal down formation remain largely unknown.
• Understanding these mechanisms offers insights into environmental adaptation and evolutionary pathways.

Purpose of the Study:

• To investigate the molecular basis for the difference in natal down growth between altricial and precocial birds.
• To identify key signaling pathways and genes involved in regulating feather development in early avian life stages.

Main Methods:

• Comparative transcriptomic analysis of anterior dorsal (AD) and posterior dorsal (PD) skin in zebra finches.
• Investigated the role of the fibroblast growth factor (FGF)/Mitogen-activated protein kinase (MAPK) signaling pathway.
• Utilized ectopic expression of FGF16 in chicken skin to validate findings.

Main Results:

• Sonic hedgehog (SHH) expression was higher in down-covered PD skin compared to naked AD skin in zebra finches.
• The FGF/MAPK pathway, particularly FGF16, was implicated in suppressing natal down growth.
• Ectopic FGF16 in chickens mimicked zebra finch AD skin by downregulating SHH and upregulating FGF10, inhibiting feather bud elongation.

Conclusions:

• FGF16 signaling acts as a suppressor of natal down elongation, leading to the naked skin phenotype in altricial bird embryos.
• This study elucidates a molecular mechanism driving the divergence in feather development between altricial and precocial birds.
• Findings contribute to understanding the genetic basis of adaptation in avian development.