Research team finds mice and humans express genes differently

genes
This image shows the coding region in a segment of eukaryotic DNA. Credit: National Human Genome Research Institute

(Medical Xpress)—A large team of bio-researchers with members from the U.S. and Spain has concluded that while mice and humans have almost the same gene pool, the way those genes are expressed differ. In their paper published in Proceedings of the National Academy of Sciences, the researchers describe how they analyzed 15 different genes that were expressed in both humans and mice and found that gene expression clustered around species more so than tissue type.

Mice have of course, been used as test subjects for years—their physical makeup, it is thought, is similar enough to ours to allow for making educated guesses about how drugs and other chemicals will impact our bodies based on the way it impacts theirs. And while this model has worked well in many cases, in others it has not. In this new effort, the researchers may have found a possible clue as to why the latter occurs.

The process by which having a certain type of gene leads to the appearance of a certain trait, is known as gene expression—whereby traits can be attributable to a certain gene. Scientists have been working under the assumption that animals that are similar to us in many ways, probably experience gene expression in similar ways as well. This may not be the case however, as the researchers found that gene expression in different types of in mice were more alike than same tissue types in humans. Gene expression in in a mouse, for example, was more like gene expression in mouse liver tissue than for heart tissue in a human. In their examination, the researchers found 4,000 that were expressed differently by the two species, suggesting that the results found could not likely to be attributed to an artifact of the experimental process.

Previous studies on in differing species have found the opposite to be true, but the researches with this new effort suggest older techniques showed different results because of the types of tissue examined—heart, kidney, brain, liver, etc. all of which have close parallel functions in both species. The limited number of tissue types tended to skew the results.


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More information: "Comparison of the transcriptional landscapes between human and mouse tissues," by Shin Lin et al. PNAS, www.pnas.org/lookup/doi/10.1073/pnas.1413624111

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JVK
Nov 18, 2014
See also my comments at: http://www.the-sc...pecific/

Nutrient-dependent/pheromone-controlled adaptive evolution: a model http://www.ncbi.n...3960065/
"Two additional recent reports link substitution of the amino acid alanine for the amino acid valine (Grossman et al., 2013) to nutrient-dependent pheromone-controlled adaptive evolution. The alanine substitution for valine does not appear to be under any selection pressure in mice. The cause-and-effect relationship was established in mice by comparing the effects of the alanine, which is under selection pressure in humans, via its substitution for valine in mice (Kamberov et al., 2013)."

Nov 19, 2014
Can anyone give me a citation or link to the original paper they are referring to here? The paper they have cited is definitely not it.

JVK
Nov 19, 2014
It could be this one

Enhanced Transcriptome Maps from Multiple Mouse Tissues Reveal Evolutionary Constraint in Gene Expression for Thousands of Genes http://www.biorxi...0/010884

Excerpt: Evolutionary constraint in gene expression levels is not reflected in the conservation of the genomic sequences, but it is associated with strong and conserved epigenetic marking, as well as to a characteristic post-transcriptional regulatory program in which sub-cellular localization and alternative splicing play comparatively large roles

See also: Alternative RNA Splicing in Evolution http://jonlieffmd...volution "It now appears that alternative splicing is, perhaps, the most critical evolutionary factor determining the differences between human beings and other creatures."

JVK
Nov 19, 2014
See also: From Fertilization to Adult Sexual Behavior
http://www.hawaii...ion.html

In our section on molecular epigenetics and cell type differentiation we noted that:

"Small intranuclear proteins also participate in generating alternative splicing techniques of pre-mRNA and, by this mechanism, contribute to sexual differentiation in at least two species, Drosophila melanogaster and Caenorhabditis elegans..."

It's not surprising the the mechanisms are also conserved in the mouse to human models of cell type differentiation.


JVK
Nov 24, 2014
The link they provided is open access.

See: "...the transcript isoform repertoire was found to be markedly different between species (1, 2). "

Unless you understand transcription in terms of isoform repertoires, you may not realize what they're saying. Excerpts from citations 1 and 2:

1) "...because organ-dependent mRNA expression levels within individual species have been largely conserved during vertebrate evolution (6, 7), it seems unlikely that changes in gene expression (GE) account for the majority of phenotypic diversity among vertebrates."

2) "...changes in splicing patterns often contribute to evolutionary rewiring of signaling networks."

See also the molecular epigenetics section of our 1996 review. Cell type differentiation is nutrient-dependent and RNA-mediated via amino acid substitutions that are fixed in organized genomes by the pheromone-controlled physiology of reproduction. Theories that link mutations to increased organismal complexity are ridiculous.

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