Article: Comparative genomics: Difference of expression
- From: "Robert Karl Stonjek" <rstonjek@xxxxxxxxxxxxxx>
- Date: Thu, 9 Mar 2006 01:44:05 -0500 (EST)
Nature 440, 161 (9 March 2006) | doi:10.1038/440161a
Comparative genomics: Difference of expression
Rasmus Nielsen
Abstract
Evolutionary studies tend to focus on alterations in proteins. But
evolutionary change can often occur through modified gene expression, a
process that is now under investigation with species-specific microarrays.
Gene expression, the major determining factor of protein abundance in the
cell, is regulated by various mechanisms, such as protein binding to the DNA
sequence and interference by small RNA molecules. On page 242 of this
issue1, Gilad et al. describe their study of gene expression in four
primates. Their work is aimed at identifying similarities and differences in
gene expression between humans and their nearest relatives.
As we elucidate the complex molecular machinery that controls gene
expression, our ignorance of its role in evolution is becoming increasingly
alarming. In most cases, we know little about the way in which gene
expression is involved in how organisms adapt to new environments or
otherwise evolve. It has long been hypothesized that adaptation over short
evolutionary time may often proceed by modifications in the regulation and
interaction of genes rather than in the protein gene-products themselves2.
Proteins tend to interact in complex networks, and so small changes in the
abundance of one protein may have profound consequences. At the DNA level
there may be many different mutations that affect gene-expression levels,
but very few potentially beneficial mutations that directly affect protein
function. Nonetheless, for convenience, most evolutionary studies have
focused on protein evolution, leaving gene expression as one of the great
unknowns in evolutionary biology.
Gilad et al.1 make new strides in this field of research. They compare
gene-expression data in humans, chimpanzees, orangutans and rhesus monkeys
to identify genes that have changed their level of expression in the human
lineage. This research differs from earlier studies3, 4 in using microarrays
designed specifically for each species. Microarrays consist of a number of
probes that bind messenger RNA from specific genes (mRNA is the linking
molecule between a gene and the protein it encodes). By determining how much
mRNA binds to each probe, the relative abundance of mRNA from each gene can
be assessed. However, if the same microarray is used for all species,
results may differ between species because of species-specific mutations
that affect the binding affinity of the probes. Although this problem can be
partially circumvented by removing genes that have such mutations,
species-specific microarrays are the only known way to obtain a fair
comparison among several divergent species without the loss of any genes.
Full Text at Nature
http://www.nature.com/nature/journal/v440/n7081/full/440161a.html
Posted by
Robert Karl Stonjek
.
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