The different steps of skin formation in vertebrates.

Abstract

Skin morphogenesis occurs following a continuous series of cell-cell interactions which can be subdivided into three main stages: 1-the formation of a dense dermis and its overlying epidermis in the future appendage fields (macropattern); 2-the organization of these primary homogeneous fields into heterogeneous ones by the appearance of cutaneous appendage primordia (micropattern) and 3-cutaneous appendage organogenesis itself. In this review, we will first show, by synthesizing novel and previously published data from our laboratory, how heterogenetic and heterospecific dermal/epidermal recombinations have allowed us to distinguish between the respective roles of the dermis and the epidermis. We will then summarize what is known from the work of many different research groups about the molecular signaling which mediates these interactions in order to introduce the following articles of this Special Issue and to highlight what remains to done.

Transdifferentiation of corneal epithelium into epidermis occurs by means of a multistep process triggered by dermal developmental signals

“…They are subsequently reformed, and this delay seems to correspond to the time required by the cells of the basal layer of the corneal epithelium to dedifferentiate and express a factor required for condensation induction and maintenance. Our results thus support a model of epidermal appendage differentiation whereby a competent dermis provides a general signal to instruct the epidermis to start appendage formation (57). In turn, the epidermis self-organizes into placodes, by means of an activator-inhibitor model (58), which then induce the formation of dermal condensations.…”

The Development of the Integumentary System in Dogs

“…Similar to all embryogenesis, hair follicle development requires an interaction between the two main tissues. The morphology of hair follicle formation as described herein is only possible because of the cell signaling between epidermal and mesenchymal cells, which have an inductive role on one another through the production and release of messenger molecules [9,10].…”

“…The skin and its appendages were studied in pigs by Meyer and Görgen [5], by Bragulla [6] in horses, by Bragulla et al [7] in cats and by Sengel [8] in mice. In general, this system has also been studied in mammals by Hardy [9] and in other vertebrates by OliveiraMartinez et al [10], who have focused on the molecular events that surround tissue differentiation.…”

Epidermal transient down‐regulation of retinol‐binding protein 4 and mirror expression of apolipoprotein Eb and estrogen receptor 2a during zebrafish fin and scale development

“…The molecular mechanisms responsible for epidermal specification and epithelial-mesenchymal signaling during epithelial appendage development are likely to be conserved in vertebrate species (Pispa and Thesleff, 2003;Olivera-Martinez et al, 2004). Functions of zebrafish genes, such as ⌬Np63 (Bakkers et al, 2002;Lee and Kimelman, 2002), perp (Nowak et al, 2005), and lgl2 (Sonawane et al, 2005), required in epithelium-forming tissues, seems to be conserved from fish to mammals.…”