carbocyanines and cyclopamine

Dorsal commissural axons in the developing spinal cord cross the floor plate, then turn rostrally and grow along the longitudinal axis, close to the floor plate. We used a subtractive hybridization approach to identify guidance cues responsible for the rostral turn in chicken embryos. One of the candidates was the morphogen Sonic hedgehog (Shh). Silencing of the gene SHH (which encodes Shh) by in ovo RNAi during commissural axon navigation demonstrated a repulsive role in post-commissural axon guidance. This effect of Shh was not mediated by Patched (Ptc) and Smoothened (Smo), the receptors that mediate effects of Shh in morphogenesis and commissural axon growth toward the floor plate. Rather, functional in vivo studies showed that the repulsive effect of Shh on postcommissural axons was mediated by Hedgehog interacting protein (Hip).

Topics: Age Factors; Animals; Axons; Body Patterning; Carbocyanines; Cell Adhesion Molecules, Neuronal; Cell Line; Chick Embryo; Cloning, Molecular; Diagnostic Imaging; Embryo, Mammalian; Embryo, Nonmammalian; Embryonic Induction; Gene Expression Regulation, Developmental; Hedgehog Proteins; Hybridomas; In Situ Hybridization; In Vitro Techniques; Membrane Proteins; RNA, Antisense; RNA, Small Interfering; Spinal Cord; Trans-Activators; Veratrum Alkaloids

Feathers are formed following a series of reciprocal signals between the epithelium and the mesenchyme. Initially, the formation of a dense dermis leads to the induction of a placode in the overlying ectoderm. The ectoderm subsequently signals back to the dermis to promote cell division. Sonic Hedgehog (Shh) is a secreted protein expressed in the ectoderm that has previously been implicated in mitogenic and morphogenetic processes throughout feather bud development. We therefore interfered with Shh signaling during early feather bud development and observed a dramatic change in feather form and prominence. Surprisingly, outgrowth did occur and was manifest as irregular, fused, and ectopic feather domains at both molecular and morphological levels. Experiments with Di-I and BrdU indicated that this effect was at least in part caused by the dispersal of previously aggregated proliferating dermal cells. We propose that Shh maintains bud development by localizing the dermal feather progenitors.

Topics: Animals; Biomarkers; Bone Morphogenetic Protein 2; Bone Morphogenetic Protein 4; Bone Morphogenetic Proteins; Bromodeoxyuridine; Carbocyanines; Cell Division; Chick Embryo; Feathers; Hedgehog Proteins; In Vitro Techniques; Limb Buds; Signal Transduction; Skin; Trans-Activators; Transforming Growth Factor beta; Veratrum Alkaloids