Researchers spot a clue as to why human and mouse genomes overlap Premium

Discovering ultra-conserved elements in the genome and their role in limiting protein production in mice testes.

Eighty million years ago humans, rats, and mice shared the same mammalian ancestor.

More recently, researchers made the astonishing discovery that even today our genomes contain close to 500 segments that have remained totally unchanged since then. These segments are called ultra-conserved elements (UCEs). Nearly all the UCEs are also highly unchanged in the chicken and dog genomes, and many are significantly conserved in fish, too.

What biological constraint maintained the UCEs intact in so many different genomes for these tens of millions of years?

For a long time scientists had no idea — so much so that our ignorance was considered profound.

But a team made a breakthrough this year. Researchers led by David J. Elliott of Newcastle University in the UK reported in EMBO Journal that a UCE in a mouse gene has an important role in limiting the production of the protein encoded by this gene.

Using genetic engineering, they deleted this gene in mouse testes, and found that these mice over-produced the corresponding protein in their testes. The overproduction resulted in death of the sperm-producing cells and the mice becoming infertile.

This result suggested that if the UCE underwent any change that interfered with its role in limiting that protein’s levels, it would result in loss of sperm production. Thus the altered UCE wouldn’t be transmitted to the next generation, accounting for the maintenance of the UCE across species.