GENETIC diseases such as diabetes and Huntington’s disease may be an evolutionary hangover from our primitive ancestors. This surprising discovery might make it possible to study human diseases in fish and insects – unlikely as that seems – as well in the more usual mice.
To discover when disease-related genes emerged in humans, Tomislav Domazet-Loao from the Ruder Boakovic Institute in Zagreb, Croatia, and colleagues compared our genome with that of organisms as diverse as bacteria and primates, which come from different stages in the evolution of living species.
The team found that we have inherited a far greater proportion of disease-related genes from organisms that evolved early on than from our closer relatives, such as rodents or other primates, although they don’t yet know why. For example, while a massive 40 per cent of our genes come from bacteria, the proportion of disease genes that come from bacteria is even larger, at 60 per cent.
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By the time zebrafish evolved from a common ancestor of fish and humans about 400 million years ago, 98 per cent of all our disease genes had already appeared. But just 0.45 per cent of these genes originate from early mammals around 240 million years ago (Molecular Biology and Evolution, ).
Mice are the usual choice for studying human disease because most of their genes have direct human equivalents. However, we could now use insects or fish to find chemicals that alter the expression of disease genes, says co-author Diethard Tautz from the Max Planck Institute for Evolutionary Biology in Plön, Germany. Sara Mole, a geneticist at University College London, agrees. Using organisms that are easier to manipulate genetically than mice could speed up research, she says.
