Chapel Hill - A new study at the University of North Carolina at Chapel Hill is the first to establish that a mutation in a gene associated with about 20 percent of all cases of hereditary deafness found in Whites is also found in blacks.

"There have been some reports in the scientific literature on Caucasians but only a small study on African-Americans, and they didn't find the mutation," said Dr. Elizabeth M. Rohlfs, clinical assistant professor of pathology and laboratory medicine at UNC-CH School of Medicine.

Rohlfs and her colleagues tested DNA samples of 500 Whites and 500 Blacks for the mutation known as 35-delete-G (35delG). Healthy carriers of the mutation carry only one copy, from either their mother or father. When each parent has a copy, one in four offspring risk inheriting a pair and is born deaf. These are the odds for inheriting a recessive genetic trait.

"We found a 2 percent carrier frequency of 35-delete-G in Caucasians and a 0.4% carrier frequency in African- Americans," Rohlfs said. In the North Carolina general population, this translates to a frequency of one in 10,000 for whites and 1 in 250,000 for blacks.

The findings will be reported Wednesday October 20 to the annual meeting of the American Society of Human Genetics in San Francisco. They provide important population-based statistics that will help form the basis for wider genetic screening for 35delG.

"This study suggests that 35-delete-G may account for a significant proportion of recessive deafness not linked to another genetic disorder in North Carolina," Rohlfs said.

The mutation, a deletion of a single nucleic acid, occurs in the gene responsible for connexin 26, a protein crucial to communication between cells, including cells within the inner ear.

The protein makes the infinitesimally small gap junctions in cell membranes that allow molecules to pass through to adjacent cells. In the
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Contact: Lynn Wooten
Lwooten@unch.unc.edu
919-966-6046
University of North Carolina School of Medicine
19-Oct-1999