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Diprosopus (Greek , "two-faced", from , ', "two" and , ' (), "face", "person"; with Latin ending), also known as craniofacial duplication (cranio- from Greek , "skull", the other parts Latin), is an extremely rare congenital disorder whereby parts (accessories) or all of the face are duplicated on the head.〔(Definition of diprosopus ) at MedicineNet. Accessed 8 January 2006.〕〔('Miracle baby' is feted in India ) at (BBC News ). Accessed 10 April 2008.〕 == Development == Although classically considered conjoined twinning (which it resembles), this anomaly is not normally due to the fusion or incomplete separation of two embryos. It is the result of abnormal activity by the protein SHH (sonic hedgehog). (The name of this protein was inspired by the Sonic the Hedgehog video game character and is part of an idiosyncratic naming tradition in molecular biology research.) SHH and its corresponding gene have been found to play an important role in signaling craniofacial patterning during embryonic development. Among other things, SHH governs the width of facial features. In excess it leads to widening of facial features and to duplication of facial structures.〔 The greater the widening, the more structures are duplicated, often in a mirror image form. This has been demonstrated in the laboratory by introducing pellets of the SHH protein into chicken embryos, resulting in chickens with duplicate beaks. Inadequate amounts of that protein lead to opposite conditions such as cyclopia where facial features are insufficiently developed. Healthy brain development is also dependent on the signaling function of SHH.〔(Sonic Hedgehog shapes the brain ). (ScienceDaily ), 13 March 2001. 〕 During embryonic development, SHH directs embryonic cells to organize in specific areas that later become specialized neural tissues, thus controlling the size and shape of brain structures. 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「Diprosopus」の詳細全文を読む スポンサード リンク
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