Holoprosencephaly: the Power of the Sonic Hedgehog Gene Essay
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Holoprosencephaly (HPE) is a rare structural irregularity that occurs when the forebrain is not successful in dividing into 2 separate hemispheres and ventricles. There are different ways in which the forebrain can divide. Alobar HPE is when 1 ventricle separates, but the hemispheres remain attached. Semi lobar and lobar are when either the lobes dissipates but the hemispheres are still attached or the lobes are halfway divided but the lobes are fused ventrally. This defect is visible with the naked eyes due to this failure to divide. The brain forms a different shape causing the skull to conform and take shape of this abnormality. Visible symptoms include a cleft lip or the development of only 1 eye. This defect is caused by a mutation on the Sonic Hedge Hog (shh) gene. This gene’s main purpose is to regulate many features of embryonic development, which includes growth of fingers and toes and the organization of brain neurons. It also controls cell division of the adult stem cells and has also been found in some cases of cancer. If the shh protein drops below 50 in the developmental phase, the fetus is most likely to develop Holoprosencephaly. Since the shh gene controls most of the embryonic development, it is the most commonly mutated gene it can also cause mutations in other genes closely associate with it such as the PAFAH1B1 gene Defection of this malformation is fund through MRI imaging and CT scans. However, an MRI has proven to be more accurate and efficient in perceiving Holoprosencephaly. The images produced by the MRI imaging shows the parts of the brain that was not separated, and the shape and form it undertook when the division was not possible. Most babies with this mutated gene are usually born, however, depending on which type of Holoprosencephaly they have, life expectancy ranges to about 3 months to 12 years.
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