Fred Hutchinson Cancer Research Center scientists have, for the first time, mapped a young gene’s short, dramatic evolutionary journey to becoming essential, or indispensable. In a study published online June 6 in Science, the researchers detail one gene’s rapid switch to a new and essential function in the fruit fly, challenging the long-held belief that only ancient genes are important.
“We really haven’t paid much attention to what is new, because there’s so much emphasis on what is old,” said Harmit Singh Malik, Ph.D., a member of the Hutchinson Center’s Basic Sciences Division and senior author of the study. “This work breaks the paradigm that new genes by definition are not really that important, because if they were important they would be much older.”
The less a gene has mutated over the millions or billions of years of its lifespan, the more likely it is to play a key role for its host. But it turns out that the converse is not necessarily true. Young and rapidly evolving genes can be indispensable too. Scientists at the University of Chicago were surprised to find in 2010 that young genes acquire essential functions in the same proportion as old genes, but nobody had explored the biology behind the phenomenon.
Malik and his colleagues examined one such case in detail, starting from the gene’s birth and its pathway to a new purpose and evolutionary importance. The fruit flyDrosophila melanogaster, a common model organism in laboratory studies, is host to the relatively new gene Umbrea, which duplicated and began to diverge from its parent gene a mere 15 million years ago.
The scientists compared Umbrea with its parent gene, HP1B, by looking at where each gene’s protein product tracks within the cell. Both proteins coat chromosomes, but the Umbrea protein specifically hones to centromeres, the specialized centers that help chromosomes duplicate and segregate when cells divide.