A new USC Stem Cell study has identified key gene regulators that enable some deafened animals—including fish and lizards—to naturally regenerate their hearing. The findings could guide future efforts to stimulate the regeneration of sensory hearing cells in patients with hearing loss and balance disorders. The study focuses on two cell types in the inner ear: the sensory cells that detect sound, and the supporting cells that create an environment where sensory cells can thrive. In highly regenerative species such as fish and lizards, supporting cells can also transform into replacement sensory cells after injury—a capacity absent in humans, mice and all other mammals. The scientists determined how genes normally only found in the sensory cells can be re-activated in the supporting cells of regenerative species. To achieve that, the scientists determined how the genome is folded in the sensory cells and supporting cells of the inner ears of regenerative zebrafish and green anole lizards. They then compared DNA control elements for sensory genes in zebrafish and green anole lizards to those in mice, which cannot replace sensory hearing cells after injury. Their experiments revealed a class of DNA control elements known as “enhancers” that, after injury, amplify the production of a protein called ATOH1, which in turn induces a suite of genes required to make sensory cells of the inner ear. Using CRISPR the scientists deleted five of these enhancers in zebrafish, impairing both the formation of sensory hearing cells during development and their regeneration following injury.

In meerkat society a dominant female is in charge, growling, biting, pushing and shoving to keep others in line. The matriarch’s bullying behavior is fueled by high levels of testosterone that can surge to twice those of her male counterparts when she’s pregnant. But while testosterone gives her a competitive edge and helps her keep the upper hand, it can also take a toll on the health of her developing offspring, Duke University researchers report.