ANN ARBOR---On June 23, 1997, a mouse was born in a laboratory at the University of Michigan Medical School. This mouse---affectionately known as Sebastian---was different from his seven litter mates, his mother and father and all the other mice in his ancestral line. Thanks to U-M scientists and genetic engineering technology, this mouse could hear.
Sebastian is a shaker-2 mouse---a strain descended from a mouse exposed to X-rays in 1928. Because of an X-ray-induced mutation on mouse chromosome 11, which has been passed on to later generations, shaker-2 mice are born with inner ear defects which cause deafness and balance abnormalities.
In a paper published in the May 29 issue of Science, U-M scientists describe how they used transgenic technology to find the recessive mutated gene responsible for deafness in shaker-2 mice. By injecting short sections of normal cloned DNA into fertilized mouse eggs and then waiting to see which DNA clone produced a hearing mouse, U-M scientists were able to focus their search for the mutant gene in a small area and find it faster than would have been possible without transgenic technology.
The U-M study represents the first permanent correction of a deafness-related genetic mutation and the fifth time that identification of a deafness gene in mice helped scientists find a similar gene in humans---according to Sally A. Camper, associate professor of human genetics in the U-M Medical School, who directed the research.
"There are at least 12 other deafness-related mutations where the gene remains unknown," Camper said. "Finding the defective gene is the first step toward developing new treatments which someday could restore hearing in children and adults."
"The next step is to develop delivery vehicles to introduce the normal gene into
inner ear cells of individuals who carry these deafness genes," said Yehoash
Raphael, assistant professor of otolaryngology in the U-M Medical School, who
Contact: Sally Pobojewski
University of Michigan