Dorsal dermis development depends on a signal from the dorsal neural tube,which can be substituted by Wnt-1

To investigate the origin and nature of the signals responsible for specifi cation of the dermatomal lineage, excised axial organs in 2-day-old chick e mbryos were replaced by grafts of the dorsal neural tube, or the ventral ne ural tube plus the notochord, or aggegates of cells engineered to produce S onic hedgehog (Shh), Noggin, BMP-2, Wnt-1, or Wnt-3a. By E10, grafts of the ventral neural tube plus notochord or of cells producing Shh led to differ entiation of cartilage and muscles, and an impaired dermis derived from alr eady segmented somites. In contrast, grafts of the dorsal neural tube, or o f cells producing Wnt-1, triggered the formation of a feather-inducing derm is. These results show that the dermatome inducer is produced by the dorsal neural tube. The signal can be Wnt-1 itself, or can be mediated, or at lea st mimicked by Wnt-1. (C) 2001 Elsevier Science Ireland Ltd. All rights res erved.