On Jan. 7, 2025, researchers at the Francis Crick Institute, MRC Harwell Institute and UCL Queen Square Institute of Neurology announced they have identified the genetic cause for the most common type of hearing loss in children with Down syndrome.

Down syndrome affects around 1 in 800 new births and is caused by an extra third copy of chromosome 21. About half of children with Down syndrome have hearing loss due to otitis media with effusion (OME), which is inflammation and fluid in the middle ear, also known as glue ear. In research published in eLife, the research team, led by MRC Harwell Institute, looked at mice that model Down syndrome by having additional copies of key genes which mirror the extra copy of chromosome 21 in humans.

They observed that all mice of a strain called Dp1Tyb with a third copy of a genetic region on mouse chromosome 16 (which mirrors chromosome 21) had fluid in their middle ear and a thickened middle ear lining from as early as three weeks old. These Dp1Tyb mice also needed louder sounds to initiate a response in their brains, suggesting they had hearing loss. Using gene mapping, the team narrowed down that a gene called Dyrk1a, found on a smaller segment of Dp1Tyb, was responsible for the OME. Extra copies of Dyrk1a have been linked to heart defects in Down Syndrome, as well as other effects like facial changes and cognitive impairment.