A study by researchers at the Wellcome Trust Centre for Human Genetics at Oxford University has uncovered the key role played by a single gene in how groups of animals diverge to form new species. The study, published today in the journal Nature, restored fertility to the normally-infertile offspring of two subspecies of mice, by replacing part of the Prdm9 gene with the equivalent human version. Despite the nearly 150 million years of evolution separating mice and humans, these ‘humanized’ mice were completely fertile.
New animal species form when groups of animals become isolated and as a result, begin to separate through evolution (a process known as speciation). When these isolated populations meet later, they might be able to breed with each other, but the male offspring are often infertile. Horses and donkeys are an example of such speciation: they can interbreed, but their offspring, mules, are infertile.
‘Our work studied similar infertility in hybrid house mice, whose two parents come from different subspecies found in Western and Eastern Europe’, says Dr Ben Davies from the Nuffield Department of Medicine, the first author on the study. These two sub-species are therefore on the verge of splitting into two entirely different species, since like mules, their offspring are infertile.
Dr Davies and his colleagues studied the Prdm9 gene: this gene is already known to have a role in infertility in mice from different species, and is in fact the only known speciation gene in mammals. However, how speciation might link up to infertility was unknown.
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