Molecular mechanisms controlling dorsal dermis generation from the somitic dermomyotome.

The initiation of the development of skin appendages (hair/feathers/scales) requires a signal from the competent dense dermis to the epidermis (Dhouailly, 1977). It is therefore essential to understand how to make a competent dermis. In recent years, a few studies have focused on the development of the dorsal dermis from the somitic dermomyotome. Our first aim in this review is to attempt to reconcile the available data on the origin of the dorsal dermis and summarize the present knowledge on the molecular mechanisms implicated in dermal lineage induction. Secondly, we open the discussion on the formation of a loose pre-dermal mesenchyme and more importantly of a dense dermis capable of participating in appendage development. To go further we draw a comparison between the chick and mouse systems to gain a new insight into how to initiate appendage morphogenesis and regulate the extent of hair/feather fields.