Holy Holoprosencephaly!

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Holoprosencephaly (HPE) has a range of disorders from cycloptic eye to cleft palate. There are many genetic and environmental influences in the development of HPE. The sonic hedgehog (Shh) pathway has been deeply explored and has relation so HPE. The regulation of Shh and other genes involved are important for proper mid line separation. This separation is what allows two eyes to develop. When Shh is not produced, there is no mid line separation and cyclopia develops, but when Shh has reduced production there is some mid line separation. The partail mid line separation causes the eye to be not spaced correctly and be close together resulting in hypotelorism. Other factors such as prechordal plate (PCP) axial midline, and Six 3 are also needed for proper mid line separation. PCP is a source of Shh ligans, when PCP is surgically removed cyclopia forms. The same goes for loss of axial mid line. Organisms lacking Six3 cause WNTs to not be inhibited this causes the anterior structures to disappear resulting in atelencephaly.This is described in the illustration below.
It is obvious that there are many ways that proper mid line separation can be disrupted and that a multitude of genes act together to prevent HPE. HPE is not a common human disease, which makes it difficult to research and when HPE is present in other organisms, such as mice, frogs and fish, the learning do not always apply to the human population. I believe the key to understand HPE is in the Shh pathway and the different molecules that are effects and act on that pathway.

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This page contains a single entry by Lacey Bebout published on November 16, 2011 9:30 AM.

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