Have you ever felt like you're really a fish? That you love the water, you want to swim forever, that you should don an artificial tail and eat kelp for the rest of your life? Then congratulations, you're crazy. But by coincidence some of your psycho-cells agree with you, hiding gene expression patterns that date back to the fish and probably beyond.
In 2009, Timothy Hughes at the University of Toronto, Canada, worked with a team of researchers to investigate evolutionary alterations in gene regulation in the five different vertebrates. They found that although the specialized DNA sequences that regulate the expression of the genes seem to have changed beyond recognition over the hundreds of millions of years since the clades parted evolutionary company, the actual patterns of gene expression remain closely conserved.
"There are clearly strong evolutionary constraints on tissue-specific gene expression. Many genes show conserved human/fish expression despite having almost no nonexonic conserved primary sequence," Hughes said.
The authors studied 3074 genes that were present as a single unambiguous copy in each of the five genomes. The similar expression profiles they uncovered suggest the existence of a basic ancestral pattern of expression in each tissue, the so-called 'inner fish'.
The strongest similarities were seen in brain tissue. Hughes said, "This relatively low divergence of gene expression in brain supports the hypothesis that neurons participate in more functional interactions than cells in other tissues – imposing constraints on the degree of alteration that can be tolerated". Genes expressed in tissues subject to greater environmental influence (such as intestine, stomach and spleen) may be more likely to take on new roles and diverge in expression as a means of adaptation.
Although this study only investigated vertebrates, these expression profiles may go much further back into our past. The authors conclude, "It is likely that the conservation of gene expression extends beyond the base of vertebrates, coexpression of neuronal genes, for example, has been observed as far as nematodes."
Hughes team found that while the actual genes have evolved beyond recognition, as you may notice from your inability to expand to twice your normal size as a panic reaction, the actual profiles of gene expression in critical organs are extremely similar. You might be building a completely different heart, according to very different instructions, but there are certain steps and stages you must follow whether you're feathered or froggy.
These similarities appear to be enforced by function, not by how much the genome actually differs from species to species. These conserved profiles were found across very varied species no matter how much their DNA appeared otherwise similar. There are simply only so many ways you can alter the heart-construction-procedure without fatally fouling it up.
Creepily, as revealed above, it bis one of the most conserved constructions is the brain - meaning that you might have more mind in common with carp than you expect. Thanks a lot, nature: the one superhero we're genetically equipped to be is Aquaman.
The Daily Galaxy via Conserved Gene Expression
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