A study carried out by researchers from Washington University School of Medicine have found that mice lacking the FGF20 protein were deaf from birth. This was because the area of the inner ear containing a type of hair cell had not developed normally, as it became stuck in an earlier developmental stage. This suggests FGF20 is essential for the normal development of these important cells that are necessary for hearing. The findings may provide a new target for researchers aiming for a better understanding of deafness due to hair cell defects in humans.