Bruce Riley, a Texas A&M University biologist, has 20,000 zebrafish and a $1.5 million federal grant to help him study how hair cells regenerate in zebrafish and to develop a cure for deafness.

Riley studies the inner-ear development of the striped tropical minnows because the genes of all vertebrates are remarkably similar.

“Our research is founded on the simple idea that the genes that control the development of the inner ear zebrafish are the same in fish and humans,” Riley said. “We’re trying to figure out what genes control regeneration of zebrafish hair cells, which control hearing. The hope is that if we can understand them, maybe we can figure out a way to coax a similar response out of the equivalent cells in a human. I absolutely believe that’s going to happen in our lifetime. And in principle, it could literally be a cure for deafness.”

Riley’s research program, which broadly uses zebrafish as a model by which to investigate how genes control development, received the grant renewal from the National Institutes of Health’s National Institute on Deafness and Other Communication Disorders (NIDCD).

Zebrafish are part of a group of fish considered to be hearing specialists; he said they make the perfect laboratory specimen for studying inner-ear development.

For generations, mice and fruit flies have been biologists’ best laboratory friends. But in recent decades, researchers also have embraced the ubiquitous zebrafish, which also has many lab-friendly qualities. For instance, they’re hardy, being native to the sewage-infested Ganges River in India. They also are known as a beginner’s fish, because they’re cheap, don’t die easily, weather extreme heat, and tolerate low-oxygen tension.

In his lab, Riley investigates how zebrafish regenerate hearing, a quality that most vertebrates have but that humans and all mammals seem to have lost somewhere along the evolutionary process. Researchers can zap a mature zebrafish hair cell with a laser, and a rapid regeneration response kicks in that restores the cell within 12-to-24 hours by reactivating early developmental genetic programs. It doesn’t work that way in humans: Once a hair cell dies, it’s lost forever. But figuring out the cells that control hair cell regeneration in zebrafish and how they work potentially could give insight into how to replicate that process in humans.

Riley’s lab already has made key contributions to the field. In 2010, he published a paper which showed that the disruption in zebrafish of a gene he was studying called SOX2 prevents the regeneration of a destroyed hair cell. The human ear also has that gene, but soon after birth, the amount of expression of the gene is dramatically reduced, leading Riley to conclude that the reason humans have lost their capacity to regenerate lost hair cells likely is because they don‘t have enough SOX2.

“We want to know how SOX2 works in zebrafish so it could potentially tell us if this is a good candidate for a gene therapy approach in humans,” Riley said.

To learn more about Riley and his research, visit

SOURCE: Texas A&M University