Development of the scleral ossicles, a ring of bony elements within the sclera, is directed by a series of papillae that arise from placodes in the conjunctival epithelium over a 1.5-day induction period in the chicken embryo. The regular spacing of the papillae around the corneal-scleral limbus suggests that their induction may be regulated by a reaction-diffusion mechanism, similar to other epithelial appendages. Some key placode signalling molecules, including β-catenin, are known to be expressed throughout the induction period. However, others have been studied only at certain stages or have not been successfully detected. Here we use qPCR to study the gene expression patterns of the wingless integration (WNT)/β-catenin, bone morphogenetic protein (BMP), ectodysplasin (EDA), fibroblast growth factor (FGF) and hedgehog (HH) signalling families in discrete regions of the eye throughout the complete conjunctival placode and papillae induction period. This comprehensive analysis revealed a variable level of gene expression within specific eye regions, with some genes exhibiting high, moderate or low changes. Most genes exhibited an initial increase in gene expression, followed by a decrease or plateau as development proceeded, suggesting that some genes are important for a brief initial period whilst the sustained elevated expression level of other genes is needed for developmental progression. The timing or magnitude of these changes, and/or the overall gene expression trend differed in the temporal, nasal and/or dorsal eye regions for some, but not all genes, demonstrating that gene expression may vary across different eye regions. Temporal and nasal EDA receptor (EDAR) had the greatest number of strong correlations (r > 0.700) with other genes and β-catenin had the greatest number of moderate correlations (r = 0.400–0.700), while EDA had the greatest range in correlation strengths. Among the strongly correlated genes, two distinct signalling modules were identified, connected by some intermediate genes. The dynamic gene expression patterns of the five signalling pathways studied here from conjunctival placode formation through to papillae development is consistent with other epithelial appendages and confirms the presence of a conserved induction and patterning signalling network. Two unique gene expression patterns and corresponding gene interaction modules suggest functionally distinct roles throughout placode development. Furthermore, spatial differences in gene expression patterns among the temporal, nasal and dorsal regions of the eye may indicate that the expression of certain genes is influenced by mechanical forces exerted throughout development. Therefore, this study identifies key placode signalling factors and their interactions, as well as some potential region-specific features of gene expression in the scleral ossicle system and provides a basis for further exploration of the spatial expression of these genes and the patterning mechanism(s) active throughout conjunctival placode and papillae formation.

巩膜小骨（巩膜内的一圈骨性元素）的发育由一系列乳头引导，这些乳头在鸡胚胎的 1.5 天诱导期内由结膜上皮中的基板产生。角膜 - 巩膜缘周围乳头的规则间距表明它们的诱导可能受反应扩散机制的调节，类似于其他上皮附属物。一些关键的基板信号分子，包括β-catenin, 已知在整个诱导期表达。但是，其他一些仅在某些阶段进行了研究或尚未成功检测到。在这里，我们使用 qPCR 来研究离散区域中无翼整合 (WNT)/β-连环蛋白、骨形态发生蛋白 (BMP)、外胚层增生蛋白 (EDA)、成纤维细胞生长因子 (FGF) 和刺猬 (HH) 信号家族的基因表达模式整个结膜基板和乳头诱导期的眼睛。这种综合分析揭示了特定眼部区域内基因表达水平的变化，一些基因表现出高、中或低的变化。大多数基因表现出基因表达的初始增加，然后随着发育的进行而减少或趋于平稳，这表明某些基因在短暂的初始阶段很重要，而其他基因的持续升高的表达水平是发育进程所必需的。这些变化的时间或幅度，和/或整体基因表达趋势在颞部、鼻部和/或背眼区域对于一些但不是所有基因不同，表明基因表达可能在不同的眼部区域有所不同。颞部和鼻部 EDA 受体（EDAR ) 与其他基因的强相关 (r > 0.700) 最多，而β-catenin的中相关 (r = 0.400–0.700) 最多，而EDA具有最大的相关强度范围。在强相关的基因中，确定了两个不同的信号模块，通过一些中间基因连接。这里研究的从结膜基板形成到乳头发育的五种信号通路的动态基因表达模式与其他上皮附属物一致，并证实了保守的诱导和模式信号网络的存在。两种独特的基因表达模式和相应的基因相互作用模块表明在整个基板开发过程中具有不同的功能。此外，眼睛颞部、鼻部和背部区域基因表达模式的空间差异可能表明某些基因的表达受整个发育过程中施加的机械力的影响。所以，