(Santa Barbara, Calif.) UC Santa Barbara scientists turned to the simple sponge to find clues about the evolution of the complex nervous system and found that, but for a mechanism that coordinates the expression of genes that lead to the formation of neural synapses, sponges and the rest of the animal world may not be so distant after all. Their findings, titled "Functionalization of a protosynaptic gene expression network," are published in the Proceedings of the National Academy of Sciences.
"If you're interested in finding the truly ancient origins of the nervous system itself, we know where to look," said Kenneth Kosik, Harriman Professor of Neuroscience Research in the Department of Molecular, Cellular & Developmental Biology, and co-director of UCSB's Neuroscience Research Institute.
That place, said Kosik, is the evolutionary period of time when virtually the rest of the animal kingdom branched off from a common ancestor it shared with sponges, the oldest known animal group with living representatives. Something must have happened to spur the evolution of the nervous system, a characteristic shared by creatures as simple as jellyfish and hydra to complex humans, according to Kosik.
A previous sequencing of the genome of the Amphimedon queenslandica a sponge that lives in Australia's Great Barrier Reef showed that it contained the same genes that lead to the formation of synapses, the highly specialized characteristic component of the nervous system that sends chemical and electrical signals between cells. Synapses are like microprocessors, said Kosik explaining that they carry out many sophisticated functions: They send and receive signals, and they also change behaviors with interaction a property called "plasticity."
"Specifically, we were hoping to understand why the marine sponge, despite having almost all the genes necessary to build a neuronal synapse, does not have any neurons at all," said th
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University of California - Santa Barbara