MRC National Institute for Medical Research, London
Science for Health
Insights into vertebrate evolution, from the sea lamprey
06 March 2013
NIMR scientists have taken part in a large collaborative project to analyse the genome of the sea lamprey. The research is published in Nature Genetics.
Lampreys are representatives of an ancient vertebrate lineage that diverged from our own about 500 million years ago. The fossil record from the Cambrian period shows the emergence of a species with several characteristics shared with modern vertebrates, such as a cartilaginous skeleton that encases the central nervous system and provides a support structure for the branchial arches and median fins. Subsequent diversification of this lineage gave rise to the jawed vertebrates (gnathostomes), hagfish, lamprey and several extinct lineages.
The genome of the sea lamprey (P. marinus) can therefore provide insight into the ancestry of vertebrate genomes and the underlying principles of vertebrate biology. Recent advances in developmental genetics methods for the lamprey and hagfish have advanced the reconstruction of several aspects of vertebrate evolution. Given the critical phylogenetic position of the lamprey, comparing its genome to gnathostome genomes may provide insights into the structure and gene content of the ancestral vertebrate genome.
Greg Elgar (pictured), from the Division of Systems Biology, was part of a large collaboration that sought to identify genes and associated functional elements that evolved within the ancestral vertebrate lineage and to infer how these might have contributed to specific innovations in vertebrates including jaws, myelinated nerve sheaths, an adaptive immune system and a common embryonic body plan.
The researchers searched for lamprey genes that (i) had homologs in at least one sequenced gnathostome genome and (ii) had no identifiable invertebrate homolog. They identified 224 gene families that presumably trace their evolutionary origin to the ancestral vertebrate lineage and found that they were significantly enriched in functions related to myelination and neuropeptide and neurohormone signaling. These findings suggest that the elaboration of signaling in the vertebrate central nervous system might have been facilitated by the advent of new vertebrate genes.
The data were also consistent with the broadly held view that most genes involved in the regulation of morphogenesis are of ancient origin and are common throughout animals, although the non-coding sequences that orchestrate early patterning are largely unique to vertebrates. Their analysis also indicates that two whole-genome duplications are likely to have occurred before the divergence of ancestral lamprey and gnathostome lineages.
The lamprey genome provides a way to dissect the evolution of vertebrate genomes and aspects of ancestral vertebrate biology. It promises to provide insights into many other aspects of vertebrate biology, especially with continued refinements in the assembly and the capacity for direct functional analysis in lamprey embryos.
Greg Elgar
Click image to view at full-size
The timing of major radiation events within the vertebrate lineage.
Original article
Jeramiah J Smith et al (2013)
Sequencing of the sea lamprey (Petromyzon marinus) genome provides insights into vertebrate evolution
Nature Genetics Epub ahead of print. Fulltext.
© MRC National Institute for Medical Research
The Ridgeway, Mill Hill, London NW7 1AA
Top of page