Sonic Hedgehog Morphology

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Sonic hedgehog signalling function during nervous system development
13354626 Katie O’Byrne words including references

Sonic hedgehog (Shh) is a glycoprotein that is secreted by and diffuses through the developing nervous system. It is a member of the hedgehog family of signaling molecules. The Sonic hedgehog signaling cascade is an integral trafficking system that influences the pattering and growth processes involved in the development of multicellular organisms. Shh is particularly important in the dorsoventral axis of the neural tube which will be examined in detail in this essay. The mechanisms of this pathway, the impact of Shh on cell fate and the genetic regulation events that occur as a result will be explored. . . . . . . . . . .
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These determinants are influenced by the distance between the notochord and the neural tube cells.14 One of the key properties of Shh is that it functions in a dose dependent manner, it performs as a morphogen.14 It causes varying cell fates depending on its local concentration. Motor neurons are induced when the concentration is high. When the concentration is very elevated, floor plate cells are induced and when it is low central neurons are induced.14 When an early neural plate that has not yet been exposed to Shh is grown in vitro and exposed to different concentrations of SHH, different cell types are formed, showing the effect of Shh concentration on cell fate.14 Shh induces many types of ventral interneuron progenitors when it is produced ventrally in the floor plate, and notochord cells in spinal chord formation. Five different classes of neurons result from Shh selecting the identity of motor neuron progenitors. Differentiation is ended by the inhibition of Shh signaling. …show more content…
There are many complex and diverse events that take place throughout the Shh pathway, having varied but all essential effects on the development of the nervous system. Shh can signal in both short and long ranges to induce other molecules in its pathway. The processes it influences are as varied as cell survival, differentiation, proliferation and axial patterning. The molecular basis of Shh is one of the best understood of neural signaling molecules, particularly due to its homolog in Drosophila. Long distance Shh events require Shh’s auto proteolysis, lipid modification, palmitoylation and cholesteroylation.14 Cell to cell movement of Shh is via Tout-velu. Current and future research is primarily focused on developing a greater knowledge of the intricacies of this complex pathway and then beyond the developing nervous system into the adult brain where there have been found to be further Shh signaling which is also applicable to tumor

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