‘Ancestral anchovy fillet’ key to vertebrate evolution
18 June 2008
Scientists studying the ‘living fossil’ amphioxus have found evidence of dramatic genetic events that shaped the bodies of humans and all other vertebrates.
In 1991 Oxford University scientists were the first to start investigating the genetic heritage of amphioxus, a creature described as an ‘animated anchovy fillet’, which is the closest living thing to the ancestor of all vertebrates.
Now an international team including three Oxford University scientists, publishing in this week’s Nature, show that the amphioxus genome reveals evidence for two genetic events in which the entire genome of our ancient, proto-vertebrate ancestor was duplicated.
Many believe these duplications may have provided vital genetic ‘raw materials’ for evolution to shape the complex nervous system, skeleton and organs that make humans and all other vertebrates different from other animals.
‘What is remarkable is just how little amphioxus has changed from this ancient ancestor despite over half a billion years of evolution,’ said Professor Peter Holland of Oxford University’s Department of Zoology, one of the lead authors of the paper and head of the Oxford team which began the work in 1991. ‘Amphioxus gives us the basic chassis of a vertebrate-like animal, a framework that has been elaborated on by millions of years of vertebrate evolution to produce complex organs such as the brain, the kidney and the pancreas found in backboned animals today, including us.’
Susumu Ohno first suggested the idea that vertebrate genomes were shaped by ancient genome-wide duplications in 1970. However, the new research shows definitively that such duplications occurred, that they happened just before the Cambrian period over 500 million years ago, and that there were two distinct events.
‘We know that duplications of the whole genome can occur in plants and in certain amphibians,’ commented Professor Holland. ‘In each event the doubling of the genome probably occurred within a single generation as a result of a mistake in the cell division forming our ancestor’s sex cells. We can’t be sure but the duplication may have made it possible for some of the ‘spare’ genes to take on other functions or specialise in the development of more complex body parts. A lot of this genetic information would have been quickly lost but some survived to help make vertebrates the animals they are today.’
A companion paper, on which the Oxford team are also co-authors, is to be published in Genome Research. It will explore in detail the links between the amphioxus genome sequence and specific biological phenomena.
Professor Peter Holland said: ‘The amphioxus genome gives us an amazing insight into what the genome of our ancient aquatic ancestors looked like over half a billion years ago. It’s particularly gratifying that, seventeen years after research at Oxford began into amphioxus, we are finally unlocking the secrets of this fascinating animal that is so pivotal in the story of our own evolution.’
The original work at Oxford University during the 1990s was supported by the Biotechnology and Biological Sciences Research Council BBSRC (www.bbsrc.ac.uk) that also supported one of the Oxford co-authors.
For further information contact Professor Peter Holland on +44 (0)1865 271185 or email peter.holland@zoo.ox.ac.uk
Note: Images of amphioxus are available on request.
Alternatively contact the University of Oxford Press Office on +44 (0)1865 283877 or email press.office@admin.ox.ac.uk