Coelacanth survived more than 300 million years and its slow changing DNA explains why.
An international team of researchers from institutions such as Broad Institute at MIT/Harvard, the South African National Bioinformatics Institute (SANBI) at the University of the Western Cape (UWC) and Rhodes University (RU) has decoded the genome of a creature whose evolutionary history is both enigmatic and illuminating: the African coelacanth (Latimeria chalumnae). A sea-cave dwelling, five-foot long fish with limb-like fins, the coelacanth was once thought to be extinct. A living coelacanth was discovered off the African coast in 1938, and since then, questions about these ancient-looking fish – popularly known as “living fossils” – have loomed large. Coelacanths today closely resemble the fossilised skeletons of their more than 300-million-year-old ancestors. Its genome confirms what many researchers had long suspected: genes in coelacanths are evolving more slowly than in other organisms.
South African lead researcher Professor Alan Christoffels started working on a coelacanth project 10 years ago in Singapore when he was part of a team that analysed the developmental genes (HOX genes) of the coelacanth. At that time there was no completely sequenced genome sequence. About a year ago, Christoffels was invited to participate in the genomic analysis of the Coelacanth genome together with his team from UWC’s South African Bioinformatics Institute (SANBI). The team included three postdocs – namely Drs Hesse, Panji and Picone – as well as software programmer Peter van Heusden, and SANBI staff members Dr Junaid Gamieldien and Mario Jonas.
“Each of the international teams focused on one aspect of the evolution of this species. We identified what is called “gene expansions” in this ancient organism and found that some of these multiple copies of the same gene are peculiar to coelacanth. This phenomenon usually indicates new adaptations in the context of an organism’s functions. More specifically we identified a class of olfactory genes whose function fits a model for vertebrate adaptation,” says Christoffels. SANBI will be publishing the results of its analysis of olfactory genes in coelacanth shortly.