Researchers say they have identified a gene required for proper development of the inner ear in mice that may help scientists understand genetic causes of deafness in humans.

The FGF20 gene has previously been associated with inherited deafness in humans. The gene codes for a part of a family of proteins that play an important role in embryonic development, tissue maintenance and wound healing.

"When we inactivated FGF20 in mice, we saw they were alive and healthy," said senior author David Ornitz, Professor of Developmental Biology at Washington University School of Medicine in St. Louis in a released statement. "But then we figured out that they had absolutely no ability to hear."

Researchers showed that disabling the gene causes a loss of outer hair cells, a sensory cell in the inner ear that is responsible for amplifying sound. Mice missing the FGF20 gene lost about 60 percent of their outer hair cells, but the number of inner hair cells that are responsible for transmitting amplified signals to the brain appeared to be normal, according to the statement.

"This is the first evidence that inner and outer hair cells develop independently of one another," says co-author Sung-Ho Huh. "This is important because most age-related and noise-induced hearing loss is due to the loss of outer hair cells."

Researchers think that the FGF20 signaling could be a stride towards outer hair cell restoration in mammals, and that this pathway could aid in the understanding of how mammals differ from birds and other vertebrates that retain the ability to form new hair cells throughout their lives.

The study was published on Tuesday in the journal PLoS BBiology.