Essay --

Alvin Samarnmitr December 9, 2013 Bio 441 CS3219 Hedgehog Signaling Pathways Shh is a gene that plays a significant role in regulating the development of organogenesis in vertebrates. This is a recently discovered gene and over the span of only 20 years, it has become a greatly studied ligand. Not only does it function as a chemical signal necessary for development in early embryogenesis, but also continue to remain important throughout the entire life of adulthood. The signaling pathways of Shh is very intricate and due to many research reviews over the last decade, researchers have elaborated the details of this particular pathway. Some major roles that Shh contributes to are development of the brain, spinal cord, nervous system, eyes, limbs of the body, cell growth and many other important parts of the body. Because Shh signaling pathway is essential for normal embryonic development, any mutation or absence of Shh ligand will cause serious health conditions such as holoprosencephaly, cyclopia, and many other defects. Recent research shows that geneticists were able to map out the specific location of the gene in order to further understand the relationship between other genes. As research continue to progress in the growing field of developmental biology, more information about Shh will soon be discovered. Hedgehog Gene The Hedgehog gene (Hh) was first discovered by German biologist Christiane NÃ ¼sslein-Volhard, American Biologist Eric Wieschaus, and Edward B. Lewis. They were experimenting with Drosophila melanogaster fruit fly and successfully identified the crucial genes that controlled the segmentation pattern of the Drosophila embryo. Their research was published in 1980 and this won them a Nobel Prize in Physiology or ... ... requires a certain amount of both Gli activators and Gli repressors, a disruption in the balance of these proteins usually lead to exncephaly. There are many other mutants that causes the cilia to function improperly and many of these mutant leads to exencephaly, which is a cephalic disorder where the brain is formed on the exterior of the skull. Mutation or absence of hedghog will cause major health problems and defects in embryonic development. Holoprosencephaly (HPE) is one of the most common developmental defect and is caused by nonsense mutation and cytogenicc deletion. This loss of function mutation is the main cause and the symptoms can range from mild to severe cyclopia. It is a cephalic disorder in which the forebrain of the embryo fails to develop and split into two hemispheres. Resulting in abmornal brain development and deformation of the facial area.