Reverse genetics in the mouse and its application to the study of deafness

Genetic variants of the laboratory mouse can serve as useful models for hereditary deafness syndromes in humans. Recessive mutations at the shaker-1 (sh-1) and whirler (wi) loci, in chromosomes 7 and 4, respectively, both result in circling behavior and a deafness syndrome. In sh-1 homozygotes this deafness is associated with neurophysiological abnormalities that may be accompanied by structural abnormalities of the inner ear. Radiation-induced deletion mutations are being used in a strategy of reverse genetics to identify the genes defined by these mutations. Genetic analyses have refined the position of sh-1 to a chromosomal interval between break points of deletions involving the closely linked albino (c) locus. A cDNA encoding olfactory marker protein (OMP) and the anonymous locus D7OR1 have also been mapped to this interval. These clones contribute to the physical map of the sh-1 region and could be important for accessing the sh-1 gene itself. Similarly, we have identified a radiation-induced deletion of the brown (b) locus that covers the wi locus and two that do not. Thus, the wi locus has been located within a chromosome 4 interval defined by structural rearrangements, which should likewise aid in identifying closely linked molecular clones.