Study in chicks reveals causes of deafness from birth

Scientists from the UK and the US have uncovered new genetic clues to congenital deafness using chick embryos.

Congenital hearing loss - hearing impairment present at birth - is one of the most common sensory disorders in newborns and affects around one in every 1,000 babies in the UK. It can range from mild to profound and significantly impacts a child’s language development, learning, and social interaction.

A study has now identified genes, potentially linked to congenital hearing loss.

Using chick embryos, researchers from King’s College London and George Washington University, DC, USA, focused on the protein Six1, as it had previously been linked to genetic forms of deafness and through computer-based predictions, they identified more than 150 genes potentially regulated by Six1 in ear progenitor cells—cells that give rise to the inner ear.

When Six1 levels were reduced in chick embryos, four genes important for hearing development failed to activate, demonstrating the crucial role Six1 plays in early hearing structures.

Many of the genes found in the chicks are also active in developing human ears, and about a quarter fall within regions of the human genome already linked to deafness. The discovery that the same elements control these genes in birds and humans highlights their fundamental biological role.

Professor Andrea Streit, expert in developmental neurobiology at King's College London and senior author of the study, said: “It is unusual that regulatory sections of DNA, like the ones we studied, are highly conserved across species. The fact that we find them to be very similar from birds to humans indicates their critical role.”