Micro RNAs (miRNAs) are small molecules that are transcribed from genomic DNA but not translated into protein. They provide regulation to many processes, uniquely affecting many genes simultaneously. This feature makes miRNA regulation of hair-cell regeneration a particularly interesting target for pharmacological intervention. This project will examine miRNA expression in the inner ears of mice and chicks, and determine the differences in response to hair-cell damage between organs that regenerate their hair cells (chick basilar papilla) and those that do not (mouse cochlea).