Brigande and his colleagues were able to produce hair cells by transferring a key gene, called Atoh1, into the developing inner ears of mice. The gene was inserted along with green florescent protein (GFP) which is the molecule that makes a species of jellyfish glow. GFP is often used in research as a “marker” that a scientist can use to determine, in this case, the exact location of the Atoh1 expression. Remarkably, the gene transfer technique resulted in Atoh1 expression in the organ of Corti, where the sensory hair cells form.
Using this method, the researchers were able to trace how the inserted genetic material successfully led to hair cell production resulting in the appearance of more hair cells than are typically located in the ears of early postnatal mice. Crucially, Dr. Anthony Ricci, associate professor of otolaryngology at the Stanford University School of Medicine, demonstrated that the hair cells have electrophysiological properties consistent with wild type or endogenous hair cells, meaning that the hair cells appear to be functional. Based on these data, the scientists concluded that Atoh1 expression generates functional auditory hair cells in the inner ear of newborn mammals.