Parallels in signaling between development and regeneration in ectodermal organs.

Ectodermal organs originate from the outermost germ layer of the developing embryo and include the skin, hair, tooth, nails, and exocrine glands. These organs develop through tightly regulated, sequential and reciprocal epithelial-mesenchymal crosstalk, and they eventually assume various morphologies and functions while retaining the ability to regenerate. As with many other tissues in the body, the development and morphogenesis of these organs are regulated by a set of common signaling pathways, such as Shh, Wnt, Bmp, Notch, Tgfβ, and Eda. However, subtle differences in the temporal activation, the multiple possible combinations of ligand-receptor activation, the various cofactors, as well as the underlying epigenetic modulation determine how each organ develops into its adult form. Although each organ has been studied separately in considerable detail, the mechanisms underlying the parallels and differences in signaling that regulate their development have rarely been investigated. First, we will use the tooth, the hair follicle, and the mammary gland as representative ectodermal organs to explore how the development of signaling centers and establishment of stem cell populations influence overall growth and morphogenesis. Then we will compare how some of the major signaling pathways (Shh, Wnt, Notch and Yap/Taz) differentially regulate developmental events. Finally, we will discuss how signaling regulates regenerative processes in all three.

外胚层器官起源于发育中胚胎的最外层胚层，包括皮肤、毛发、牙齿、指甲和外分泌腺。这些器官通过严格调控的、顺序性的和相互的上皮 - 间充质相互作用而发育，并且它们最终呈现出各种形态和功能，同时保留再生能力。与身体的许多其他组织一样，这些器官的发育和形态发生受一系列常见的信号通路调控，例如音猬因子（Shh）、Wnt、骨形态发生蛋白（Bmp）、Notch、转化生长因子β（Tgfβ）和外胚层发育不良蛋白（Eda）。然而，时间激活上的细微差异、配体 - 受体激活的多种可能组合、各种辅因子以及潜在的表观遗传调控决定了每个器官如何发育成其成年形态。尽管每个器官都已被相当详细地单独研究，但调节其发育的信号传导中的相似性和差异所依据的机制却很少被探究。首先，我们将以牙齿、毛囊和乳腺作为代表性的外胚层器官，来探究信号中心的发育和干细胞群的建立如何影响整体生长和形态发生。然后我们将比较一些主要的信号通路（Shh、Wnt、Notch和Yap/Taz）如何差异性地调控发育事件。最后，我们将讨论信号如何调控这三者中的再生过程。