Geneticists successfully reverse gene evolution
Researchers recreate an ancient mouse gene from two of its modern descendants
You have probably heard of evolution in action - but how about evolution in reverse?
Many of the genes in our bodies have descended from ancient genes that have mutated and changed their function. Petr Tvrdik and Mario Capecchi of the University of Utah, Salt Lake City, have now managed to demonstrate this in mice by recreating an ancient gene from two of its modern descendants.
Half a billion years ago, the size of our ancestor's genome quadrupled. With four copies of every gene knocking about, genes either had to make themselves useful, or be swiftly dumped. The quadrupling meant that 13
Hox genes, which control the development of body shape, became 52. The ones that didn't mutate to do something useful were lost, so today mammals have 39
Hox genes.
Tvrdik and Capecchi focused on two that were originally duplicates but have evolved to perform different functions.
Hoxa1 controls brain stem development in the early embryo, while
Hoxb1 directs nerve growth in an area of the brain that controls facial expression.
The two genes make the same protein, but at different places in the brain, and at different times. In other words, it is the regulatrory region of the gene that differs between
Hoxa1 and
Hoxb1, not the protein-coding region.
To reconstruct the ancestral
Hox1 gene, Tvrdik and Capecchi attached the regulatory sequence from
Hoxb1 - which turns the gene on later in fetal development - to the
Hoxa1 gene. That way, one gene did the job of two. Mice with the new
Hox1 gene, but with their
Hoxa1 and
Hoxb1 genes knocked out, developed normally (
Developmental cell, DOI:10.1016/j.devcel.2006.06.016). "We constructed a gene that is fairly similar to the ancestral
Hox1 gene present in the vertebrate lineage half a billion years ago," says Tvrdik.
New Scientist: This week
12 August 2006
Rowan Hooper
Magazine issue 2564
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