Limber Cody, Wagner Günter P, Prum Richard O
Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA.
Department of Evolutionary Biology, University of Vienna, Vienna, Austria.
Evol Dev. 2025 Sep;27(3):e70016. doi: 10.1111/ede.70016.
Feathers are the most complex and diverse epidermal appendages found in vertebrates. Their unique hierarchical organization and development is based on a diversity of cell types and morphologies. Despite these presumptive feather cell types being well characterized morphologically, little is known about how gene regulation contributes to their development. Here, we use single cell and single nuclear RNA sequencing with in situ hybridization to identify and characterize cells types in embryonic chicken feathers. We show that the distinct cell morphologies correspond to feather cell types with distinct gene expression profiles. We also describe a previously unidentified cell type, the barb ridge basal epithelium, which appears to play a role alongside the marginal plate in barb ridge differentiation. A cell-cell signaling analysis provides evidence of important roles for the barb ridge basal epithelium and marginal plate signaling to the barb ridge. Furthermore, we analyze RNA velocity trajectories of developing feather cells and find distinct developmental trajectories for epidermal cells that constitute the mature feather and those that function only in feather development. Finally, we produce an evolutionary tree of feather cell types based on transcription factor expression as a test of the prior developmental hypotheses about feather evolution. Our tree is consistent with the developmental model of feather evolution, and sheds light on the influence of ancestral epidermal stratification on feather cell evolution. This transcriptomic approach to studying feather cell types helps lay the ground work for understanding the developmental evolutionary complexity and diversity of feathers.
羽毛是脊椎动物中发现的最复杂、最多样化的表皮附属物。它们独特的分层组织和发育基于多种细胞类型和形态。尽管这些假定的羽毛细胞类型在形态上已得到很好的表征，但关于基因调控如何促进其发育却知之甚少。在这里，我们使用单细胞和单核RNA测序以及原位杂交来识别和表征胚胎鸡羽毛中的细胞类型。我们表明，不同的细胞形态对应于具有不同基因表达谱的羽毛细胞类型。我们还描述了一种以前未被识别的细胞类型，即羽支嵴基底上皮，它似乎在羽支嵴分化中与边缘板一起发挥作用。细胞间信号分析提供了证据，表明羽支嵴基底上皮和边缘板向羽支嵴发出的信号起着重要作用。此外，我们分析了发育中的羽毛细胞的RNA速度轨迹，发现构成成熟羽毛的表皮细胞和仅在羽毛发育中起作用的表皮细胞有不同的发育轨迹。最后，我们基于转录因子表达生成了一个羽毛细胞类型的进化树，作为对先前关于羽毛进化的发育假说的检验。我们的树与羽毛进化的发育模型一致，并揭示了祖先表皮分层对羽毛细胞进化的影响。这种研究羽毛细胞类型的转录组学方法有助于为理解羽毛的发育进化复杂性和多样性奠定基础。
