Edited by Carlin Becker and David Martosko – ZENGER News
TEL AVIV, Israel — Delivering healthy genetic material into the inner ear cells of mice with a hereditary mutation for deafness enables the cells to function normally, according to a new study.
The study, led by Professor Karen Avraham of Tel Aviv University’s Department of Human Molecular Genetics and Biochemistry, was published in the journal EMBO Molecular Medicine on Dec. 22. It showed that the novel approach prevented the gradual deterioration of hearing in mice, which could lead to a breakthrough in treating children born with various mutations that cause deafness.
Deafness is the most common sensory disability worldwide, with about half a billion people suffering hearing loss, a figure that is expected to double in the coming decades, according to the World Health Organization. One in every 200 children is born with a hearing impairment, and one in every 1,000 is born deaf. A genetic mutation causes deafness in about 50% of cases, and a hundred different genes are associated with hereditary deafness.
“In this study, we focused on genetic deafness caused by a mutation in the gene SYNE4 — a rare deafness discovered by our lab several years ago in two Israeli families, and since then identified in Turkey and the U.K. as well,” Avraham said in a press release about the findings.
“Children inheriting the defective gene from both parents are born with normal hearing, but they gradually lose their hearing during childhood,” she said. “The mutation causes mislocation of cell nuclei in the hair cells inside the cochlea of the inner ear, which serve as soundwave receptors and are essential for hearing. This defect leads to the degeneration and eventual death of hair cells.”
Avraham’s lab used an innovative gene therapy technology and created a harmless synthetic virus that served as a delivery vehicle for a normal version of the defective gene in the mice.
“We injected the virus into the inner ear of the mice, so that it entered the hair cells and released its genetic payload,” said Shahar Taiber, one of Avraham’s students on the combined MD-PhD track. “By so doing, we repaired the defect in the hair cells and enabled them to mature and function normally.”
The treatment was administered soon after birth, and the mice’s hearing was then monitored using both physiological and behavioral tests.
“The findings are most promising,” Professor Jeffrey Holt from Boston Children’s Hospital and Harvard Medical School, a collaborator on the study, said. “Treated mice developed normal hearing, with sensitivity almost identical to that of healthy mice who do not have the mutation.”
The scientists are now developing similar therapies for other mutations that cause deafness.
“This is an important study that shows that inner-ear gene therapy can be effectively applied to a mouse model of SYNE4 deafness to rescue hearing,” said Dr. Wade Chien from the U.S. National Institute on Deafness and Other Communication Disorders and Johns Hopkins School of Medicine, who was not involved in the study.
“The magnitude of hearing recovery is impressive,” he said. “This study is a part of a growing body of literature showing that gene therapy can be successfully applied to mouse models of hereditary hearing loss, and it illustrates the enormous potential of gene therapy as a treatment for deafness.”
Additional contributors to the study included Professor David Sprinzak from the university’s School of Neurobiology, Biochemistry and Biophysics. The study was supported by the United States-Israel Binational Science Foundation, the National Institutes of Health, the European Research Council and the Israel Precision Medicine Partnership Program of the Israel Science Foundation.
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