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The Hedgehog signaling pathway (or signalling pathway; see spelling differences) is a signaling pathway that transmits information to embryonic cells required for proper development. Different parts of the embryo have different concentrations of hedgehog signaling proteins. The pathway also has roles in the adult. Diseases associated with the malfunction of this pathway include basal cell carcinoma.〔(Kimball's Biology Pages ), The Hedgehog Signaling Pathway〕 The Hedgehog signaling pathway 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 intercellular signaling molecule called Hedgehog (''Hh'') found in fruit flies of the genus Drosophila. ''Hh'' is one of Drosophila's segment polarity gene products, involved in establishing the basis of the fly body plan. The molecule remains important during later stages of embryogenesis and metamorphosis. Mammals have three Hedgehog homologues, DHH, IHH, and SHH, of which Sonic (SHH) is the best studied. The pathway is equally important during vertebrate embryonic development. 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 Hedgehog 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 Hedgehog signaling to fight this disease are being actively developed by a number of pharmaceutical companies. ==Discovery== In the 1970s, a fundamental problem in developmental biology was to understand how a relatively simple egg can give rise to a complex segmented body plan. In the late 1970s Christiane Nüsslein-Volhard and Eric Wieschaus isolated mutations in genes that control development of the segmented anterior-posterior body axis of the fly; their "saturation mutagenesis" technique resulted in the discovery of a group of genes involved in the development of body segmentation. In 1995, they shared the Nobel Prize with Edward B. Lewis for their work studying genetic mutations in Drosophila embryogenesis.〔1995 Nobel Prize for discovery of (the genetic control of early embryonic development )〕 The ''Drosophila'' hedgehog (''hh'') gene was identified as one of several genes important for creating the differences between the anterior and posterior parts of individual body segments. The fly ''hh'' gene was independently cloned in 1992 by the labs of Jym Mohler, Philip Beachy, and Thomas B. Kornberg. Some hedgehog mutants result in abnormally-shaped embryos that are unusually short and stubby compared to wild type embryos. The function of the hedgehog segment polarity gene has been studied in terms of its influence on the normally polarized distribution of larval cuticular denticles as well as features on adult appendages such as legs and antennae. Rather than the normal pattern of denticles, hedgehog mutant larvae tend to have "solid lawns" of denticles (Figure 1). The appearance of the stubby and "hairy" larvae inspired the name 'hedgehog'. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「hedgehog signaling pathway」の詳細全文を読む スポンサード リンク
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