Sponge genes suggest the origin of neurons and other cells

In fact, the gene modules expressed by many multifunctional cells in sponges are usually related to specialized cells in more complex animals (such as vertebrates). For example, spongy nerve-like cells not only express some of the presynaptic mechanisms of neurons, but also express immune genes. (If nerve-like cells monitor the microbial content of the sponge digestion chamber, these immune genes may play this role.) Sponges also have cells called pineal cells, which contract like muscle cells to squeeze the animal and remove waste. Or unwanted debris; the pineal gland cells have some sensory mechanisms that respond to nitric oxide (a vasodilator).

“Nitric oxide relaxes the smooth muscles in our blood vessels, so when our blood vessels expand, nitric oxide causes this relaxation,” Musser said. “And we have actually shown through experiments in the paper that nitric oxide is also regulating the contraction of this sponge.” He believes that, like glutamate, nitric oxide may be an early signaling mechanism that coordinates the original behavior of sponges. Part.

Musser said: “Our data is very consistent with the view that there are a large number of important functional mechanical parts in the early stages of animal evolution.” “Many early animal evolutions began to subdivide them into different cells. But it is likely that these initial cell types are very versatile. They have to do a lot of things.” The earliest animal cells, like their close relatives, protozoa, may have to be the cellular Swiss army knife. With the evolution of multicellular animals, their cells may play different roles, and this division of labor may lead to more specialized cell types. But different animal pedigrees may divide things to different degrees in different ways.

If the mixing and matching of gene modules is a key theme in early animal evolution, then comparing the arrangement and expression of these modules in different species can tell us their history—and the possible limitations that they can be shuffled at will.One researcher looking for these answers is Arnau Sebe-Pedros, He studied the evolution of cell types at the Barcelona Genome Regulation Center and published the first Cell type map In the sponge, Platform animal And 2018 comb jelly.

Sebé-Pedrós believes that the spatial arrangement of genes along chromosomes may be instructive, because genes located together can share regulatory mechanisms. “I am very shocked by the degree of conservation of gene order in animal genomes,” he said. He suspects the need to co-regulate functionally related genomes to keep them in the same chromosomal neighborhood.

Scientists are still in the early stages of understanding how cell types evolve and relate to each other. But as important as clarifying the muddy origins of animal evolution, the sponge cell map also makes a significant contribution by revealing the possibilities of animal cell biology. “It is not only important for us to understand the origin of animals,” Sebé-Pedrós said, “but also to understand things that may be completely different from what we know about other animals.”

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ability Reprinted with authorization Quanta Magazine, Edit independent publications Simmons Foundation Its mission is to improve the public’s understanding of science by covering research developments and trends in mathematics, physics, and life sciences.

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