Zebrafish, lizards use sleeping genes to restore hearing power: study
WeirdNews
They can regenerate their hearing by reactivating dormant gene regulators
(Web Desk) - Unlike humans and other mammals, regenerative species can transform their supporting cells into sensory cells to restore hearing after damage.
Anew study from USC Stem Cell scientists reveals how certain animals, such as zebrafish and lizards, can regenerate their hearing by reactivating dormant gene regulators.
The discovery provides insight into the mechanisms that could one day help humans recover from hearing loss and balance disorders.
Led by Tuo Shi, Ksenia Gnedeva, and Gage Crump from the Keck School of Medicine of USC, the research focuses on the inner ear’s two critical cell types: sensory cells, which detect sound, and supporting cells, which provide structural and functional support.
“By comparing two different regenerative vertebrates—zebrafish and lizards—to non-regenerative vertebrates such as mice, we found something that was fundamental to the way sensory cells can be replaced to restore hearing in some vertebrates,” said Crump.
The team investigated how the genome of these animals is organized to allow such remarkable regeneration.
By studying the inner ears of zebrafish and green anole lizards—both capable of regenerating sensory cells—they compared their DNA control elements, called “enhancers,” to those of mice, which lack this regenerative ability.
Enhancers are regions of DNA that boost the expression of specific genes. In regenerative species, certain enhancers activate after injury, amplifying the production of a protein called ATOH1.
This protein initiates the activation of genes necessary for the creation of new sensory cells.
Using CRISPR, the researchers deleted five key enhancers in zebrafish. The result was a significant impairment in both the development of sensory cells during embryonic stages and their regeneration after damage.
“In the past, deletion of individual enhancers most often does not have much of an effect,” said Crump. “But by targeting all five enhancers in zebrafish, we discovered their critical role in both development and regeneration.”
The team discovered that mice possess similar enhancers that function during embryonic development.
However, unlike zebrafish and lizards, mammals lose the ability to maintain these enhancers in an “open” configuration into adulthood. This closed configuration prevents supporting cells in the mammalian inner ear from replacing damaged sensory cells, effectively halting regeneration.
“What we have found is that sister cell types in regenerative vertebrates maintain open enhancers from development into adult stages, thus allowing these related cells to replace each other following damage,” said Crump.
Interestingly, the study found that the genetic deletions affected sensory cells in the zebrafish’s inner ear but not in its lateral line, a separate organ specialized for detecting water movement.
