The<unk>  is a signaling pathway that transmits information to embryonic cells required for proper cell differentiation. Different parts of the embryo have different concentrations of<unk>  signaling proteins. The pathway also has roles in the adult. Diseases associated with the malfunction of this pathway include cancer. The<unk>  is one of the key regulators of animal development and is present in all bilaterians. The pathway takes its name from its polypeptide ligand, an intracellular signaling molecule called<unk>  (Hh) found in fruit flies of the genus Drosophila; fruit fly larva lacking the Hh gene are said to resemble<unk> s. Hh is one of Drosophila's segment polarity gene products, involved in establishing the basis of the fly body plan. Larvae without Hh are short and spiny, resembling the<unk>  animal. The molecule remains important during later stages of embryogenesis and metamorphosis. Mammals have three<unk>  homologues, Desert (DHH), Indian (IHH), and Sonic (SHH), of which Sonic is the best studied. The pathway is equally important during vertebrate embryonic development and is therefore of interest in evolutionary developmental biology. In knockout mice lacking components of the pathway, the brain, skeleton, musculature, gastrointestinal tract and lungs fail to develop correctly. Recent studies point to the role of<unk>  signaling in regulating adult stem cells involved in maintenance and regeneration of adult tissues. The pathway has also been implicated in the development of some cancers. Drugs that specifically target<unk>  signaling to fight this disease are being actively developed by a number of pharmaceutical companies.
Hedgehog signaling pathway
JAK-STAT signaling pathway
Insulin signal transduction pathway
Winged-helix transcription factors
Purinergic signalling
Pyrimidine metabolism
TP53-inducible glycolysis and apoptosis regulator
Endocannabinoid system