Requirement for Shh and Fox family genes at different stages in sweat gland development (E15.5)

Sweat glands play a fundamental role in thermal regulation in man, but the molecular mechanism of their development remains unknown. To initiate analyses, we compared the model of Eda mutant Tabby mice, in which sweat glands were not formed, to wild-type mice. We inferred developmental stages and critical genes based on observations at 7 time points spanning embryonic, postnatal and adult life. In wild-type footpads, sweat gland germs were detected at E17.5. The coiling of secretory portions started at postnatal day 1 (P1), and sweat gland formation was essentially complete by P5. Consistent with a controlled morphological progression, expression profiling revealed stage-specific gene expression changes. Similar to the development of hair follicles the other major skin appendage controlled by EDA sweat gland induction and initial progression was accompanied by Eda-dependent up-regulation of the Shh pathway. During the further development of sweat gland secretory portions, Foxa1 and Foxi1, not at all expressed in hair follicles, were progressively up-regulated in wild-type but not in Tabby footpads. Upon completion of wild-type development, Shh declined to Tabby levels, but Fox family genes remained at elevated levels in mature sweat glands. The results provide a framework for the further analysis of phased downstream regulation of gene action, possibly by a signaling cascade, in response to Eda. Keywords: cell type comparison design,development or differentiation design To define target genes of Eda during sweat gland development, we carried out microarray experiments with mouse footpads that from 7 developmental time points including E15.5, E16.5, E17.5, P1, P3, P5 and 8 weeks of wild-type and Tabby mice. This dataset is E15.5.汗腺在人类体温调节中发挥核心作用，但其发育的分子机制仍不明朗。为开展相关分析，我们将无法形成汗腺的Eda突变Tabby小鼠模型与野生型小鼠进行了对比。我们基于涵盖胚胎期、出生后及成年阶段的7个时间节点的观测结果，推导出发育阶段与关键基因。在野生型小鼠足垫中，于胚胎第17.5天（E17.5）可检测到汗腺原基；分泌段的卷曲始于出生后第1天（P1），至出生后第5天（P5）时汗腺形成基本完成。与受控的形态发生进程一致，表达谱分析揭示了阶段特异性的基因表达变化。与受EDA调控的另一主要皮肤附属器——毛囊的发育类似，汗腺的诱导与初始发育进程伴随有Eda依赖的Shh通路上调。在汗腺分泌段的进一步发育过程中，在毛囊中完全不表达的Foxa1与Foxi1基因，在野生型小鼠足垫中呈渐进式上调，而在Tabby小鼠足垫中则无此现象。当野生型汗腺发育完成后，Shh的表达水平回落至Tabby小鼠的水平，但Fox家族基因在成熟汗腺中仍维持高表达状态。本研究结果为后续分析Eda响应下的基因功能阶段性下游调控（可能通过信号级联反应实现）提供了研究框架。关键词：细胞类型对比设计、发育与分化设计。为明确汗腺发育过程中Eda的靶基因，我们针对野生型与Tabby小鼠的7个发育时间点（包括E15.5、E16.5、E17.5、P1、P3、P5以及8周龄）的足垫样本开展了微阵列实验。本数据集对应E15.5时间点。