Timothy Hughes and a group of researchers from the University of Toronto in Canada have shown that gene expression in tissues with very few specialized cell types is strongly conserved by studying gene expression in chickens, frogs, mice, pufferfish and humans. Although the specialized DNA sequences that regulate the gene expression have changed dramatically over millions of years since the clades diverged from the last universal common ancestor; the patterns of gene expression are still closely conserved. Hughes states that, “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.”
Studies showed that 3074 genes as a single ‘unambiguous’ copy were present in the five genomes (chickens, frogs, mice, pufferfish and humans). This similar expression that they uncovered seems to suggest the preservation of an ancestral pattern of expression in each tissue, what has been called the ‘inner fish’. Most similarities were seen in the brain tissue which supports the hypothesis that neurons participate in more functional interactions than cells in other tissues. Also, genes expressed in tissues that are exposed to the environment (most of the digestive tract) are more likely to diverge in expression as a means of adaptation. According to the researchers, these expressions may go back well before the base of vertebrates. This could mean that all walks of life still contain this same pattern of gene expression originating from billions of years ago.
References:
Journal of Biology (2009, April 16). Conserved Gene Expression Reveals Our 'Inner Fish'. ScienceDaily. Retrieved May 12, 2009, from http://www.sciencedaily.com /releases/2009/04/090415193249.htm
Image Credit:
Chris Laughlin, National Geographic (2006)
