Evolution of Synapses

Evolution of Synapses
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Evolution of Synapses
Synaptic transmission takes place in both vertebrate and invertebrate organisms. According to Ryan and Grant (2009), synaptic transmission underlies the behavior of animals. Therefore, taking time to understand the evolution of synapses is imperative in knowing human disorders. In the Brain Science Podcast, Seth Grant says that the proteomic study of molecular components in the mammalian postsynapse points to an ancient protosynapse which existed long before neurons and metazoans evolved (Campbell, 2015). This means that the evolution of synapse can be traced back to the ancient protosynapse in unicellular organisms. Therefore, in the synaptic evolution, the signaling components evolved before nerve cells, and synaptic components evolved before the big brains
Seth Grant, in the Brain Science Podcast, points out that the synapse’s molecular composition is useful in tracing the brain evolution. However, this needs one to first conduct a proteomic study of all the proteins in the synapse to have an understanding of the evolutionary origin of synapses (Campbell, 2015). According to Ryan and Grant (2009), a proteomic study on a set of proteins like postsynaptic density and their complexes provides an evolutionary understanding of synapses. This is because the postsynaptic density present in creatures with nervous system evolved from an ancestral protosynaptic core found in both multicellular and unicellular organisms that lack a nervous system.

Comparative proteomics also shows that excitatory synapses in vertebrates have significantly evolved and become more complex than in invertebrates (Grant, 2005).
In the Brain Science Podcast, Seth Grant asserts that brain origin appears to be in an ancient set of proteins or a protosynapse present in unicellular organisms. This indicates that the evolution of single-cell organisms into metazoans or multicellular organisms was marked by the addition of a new set of proteins onto the ancestral or ancient protosynapse (Campbell, 2015). Subsequesntly, this enhancement of protosynapse co-opted and embellished the ancient protosynaptic architecture as new set of proteins or molecular compositions were inserted into the synapse between the initial neurons to form simple invertebrate organisms Pincus et al, 2008).
Additionally, Seth Grant states that a further enhancement of synaptic molecules occurred about a billion years ago as invertebrates evolved into vertebrates. This additional enhancement of molecular components in synapses between neurons has been well-maintained throughout the evolution of vertebrate organisms (Campbell, 2015). As a result, the numbers of synaptic molecular components in some vertebrates are much higher than others. Seth Grant also opines high complexity of the synaptic architecture is greatly related to the evolution of mammals’ large complex brains (Campbell, 2015). This, therefore, suggests that the evolution of highly complex synapses occurred before the big anatomically complex brains.
In conclusion, the ancestral set of proteins found in unicellular organisms are the same protein present in synapses of different vertebrates but with a more complex architecture. The most recently evolved synapses in the brain of vertebrate organisms are the most complex and diverse. However, the complexity and diversity of synaptic proteins vary from one region of the brain to another. In a nutshell, the evolution of synapses in vertebrates can be traced back to the ancient synapse which evolved before the big brains. This suggests that brains of vertebrates grew bigger and evolved further as the big synapse exploited the evolutionary new proteins to make new neurons in the brains. The evolution of synapse has, therefore, allowed the specialization and regionalization of the brain.
References
Campbell, G. (2015). “Brain Science Podcast: The Evolution of the Synapse.” moodle.esc.edu. Retrieved 1 September 2018, from https://moodle.esc.edu/mod/page/view.php?id=2030124&forceview=1.
Grant, S. G., Marshall, M. C., Page, K. L., Cumiskey, M. A., & Armstrong, J. D. (2005). Synapse proteomics of multiprotein complexes: en route from genes to nervous system diseases. Human molecular genetics, 14(suppl_2), R225-R234.
Pincus, D., Letunic, I., Bork, P., & Lim, W. A. (2008). Evolution of the phospho-tyrosine signaling machinery in premetazoan lineages. Proceedings of the National Academy of Sciences.
Ryan, T. J., & Grant, S. G. (2009). The origin and evolution of synapses. Nature Reviews Neuroscience, 10(10), 701–712.