Ventral vs. dorsal chick dermal progenitor specification.

Abstract

The dorsal and the ventral trunk integuments of the chick differ in their dermal cell lineage (originating from the somatic and somatopleural mesoderm respectively) and in the distribution of their feather fields. The dorsal macropattern has a large spinal pteryla surrounded by semi-apteria, whereas the ventral skin has a true medial apterium surrounded by the ventral pterylae. Comparison of the results of heterotopic transplantations of distal somatopleure in place of somatic mesoderm (Mauger 1972) or in place of proximal somatopleure (our data), leads to two conclusions. These are that the fate of the midventral apterium is not committed at day 2 of incubation and that the signals from the environment which specify the ventral and dorsal featherforming dermal progenitors are different. Effectively, Shh, but not Wnt -1 signalling can induce the formation of feather forming dermis from the embryonic somatopleure. Shh is not able, however, to trigger the formation of a feather forming dermis from the extra embryonic somatopleure. This brief report constitutes the first attempt, by comparing old and new preliminary results, to understand whether dermal progenitors at different sites are specified by different signalling pathways.

Skin field formation: morphogenetic events.

“…In contrast to the previous interpretation, we know at present that the somatopleure, even at its more distal part, is still malleable at E2/ E3 (Fliniaux et al, 2004). However, when this piece of somatopleure is transplanted close to the neural tube, it does not received the required signals in the correct time.…”

“…Forty years ago it was noticed the occurrence of merging between the somatopleure and the splanchnopleure in all positive cases. Recent results from my laboratory (Fliniaux et al, 2004) show that the molecular signal which arises from the splanchnopleure is not in fact irrelevant for the increase in mesodermal cell density. This fact was already noted, but previously explained only by a mechanical point of view.…”

Reprogramming adult dermis to a neonatal state through epidermal activation of β-catenin

“…Driskell et al, 2009), reflecting, at least in part, different embryonic origins (Fliniaux et al, 2004) and body sites (Rinn et al, 2006). However, whether dermal fibroblasts are organised within a differentiation hierarchy, in which some cells have greater intrinsic proliferative and differentiation potential than others (Biernaskie et al, 2009) or whether proliferative heterogeneity is primarily determined through signals from the local microenvironment, remains to be investigated.…”

The different steps of skin formation in vertebrates.

“…Indeed, before skin morphogenesis, various cellular interactions occur, which specify first the formation of dermal progenitors (OliveraMartinez et al; Fliniaux et al, 2004) …”