The Story of the Nerve-Less Sponge

20 Jun

The human nervous system evolved from a… sponge???

Who lives in a pineapple under the sea??

The Marine nerve-less sponge with genes capable of forming neural synapses… that’s who! 

UC Santa Barbara scientists previously sequenced the genome of the Amphimedon queenslandica and found that this marine sponge contains the same genes that lead to the formation of synapses, the cornerstone of the nervous system and facilitator of plasticity.

“If you’re interested in finding the truly ancient origins of the nervous system itself, we know where to look.”

Kenneth Kosik, Harriman Professor of Neuroscience Research and co-director of UCSB’s Neuroscience Research Institute, believes that the evolution of the nervous system stems from the evolutionary time period where the complex animal kingdom branched off from the common ancestor it shares with the simple sponge (the oldest known animal group with living representatives remaining today).

The current examination of the sponge’s RNA has revealed that a lot of the genes encoding for proteins in a synapse were turning on and off “as if they were doing something” (Kosik). A comparison to the same gene in other animals suggests that the sponge lacks the gene coordination or unionised expression necessary to make a synapse.

Kiosk proposes that the critical step in the evolution of the nervous system was not the formation of a new gene, but rather the regulated coordination of the pre-existing gene found in the marine sponge: “It was as if the synapse gene network was not wired together yet.” In light of these findings, Kiosk asks:

“Is the human brain just a lot more of the same stuff, or has it changed in a qualitative way?”

The real sponge…
A marine sponge, native to the Great Barrier Reef, Australia.

This paper entitled “Functionalization of a Protosynaptic Gene Expression Network” will appear in the Proceedings of the National Academy of Sciences.

Source: University of California, Santa Barbara

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