DELETION MAPPING OF THE HEAD TILT (HET) GENE IN MICE - A VESTIBULAR MUTATION CAUSING SPECIFIC ABSENCE OF OTOLITHS

Head tilt (het) is a recessive mutation in mice causing vestibular dys function. Homozygotes display abnormal responses to position change an d linear acceleration and cannot swim. However, they are not deaf. hct was mapped to the proximal region of mouse chromosome 17 near the T l ocus. Here we report anatomical characterization of hpt mutants and hi gh resolution mapping using a set of chromosome deletions. The defect in het mutants is limited to the utricle and saccule of the inner ear, which completely lack otoliths. The unique specificity of the het mut ation provides an opportunity to better understand the development of the vestibular system. Complementation analyses with a collection of e mbryonic stern (ES)- and germ cell-induced deletions localized het to an interval near the centromere of chromosome 17 that was indivisible by recombination mapping. This approach demonstrates the utility of ch romosome deletions as reagents for mapping and characterizing mutation s, particularly in situations where recombinational mapping is inadequ ate.