| First Author | British Society of Audiology short papers meeting on experimental studies of hearing and deafness. Cambridge, United Kingdom, 22-23 September 1996. Hardisty RE | Year | 1997 |
| Journal | Br J Audiol | Volume | 31 |
| Issue | 2 | Pages | 73-132 (83-4 Abstr.) |
| Mgi Jnum | J:45223 | Mgi Id | MGI:1201261 |
| Citation | British Society of Audiology short papers meeting on experimental studies of hearing and deafness. Cambridge, United Kingdom, 22-23 September 1996. Hardisty RE, et al. (1997) The characterization of the head bobber mouse mutant. Br J Audiol 31(2):73-132 (83-4 Abstr.) |
| abstractText | Full text of Abstract. The characterization of the head bobber mouse mutant. R.E. Hardisty, D.C. Hughes and K.P. Steel, MRC Institute of Hearing Research, University Park, Nottingham NG72RD The mouse mutant head bobber (hb) was created by insertional mutagenesis arising in a transgenic line carrying a plasmid phBetaAPr-1neo, which includes a portion of pSV2-neo and a human- Beta actin promotor (P. Overbeek, personal communication). Only homozygotes are affected, suggesting recessive inactivation of a gene responsible for normal inner ear development. We plan to identify this native gene involved in ear development using the transgene as a molecular tag. Overt behavioural traits of the mutant include head bobbing, hyperactivity and circling. The animal does not display a Preyer reflex. More elaborate vestibular testing has allowed a more specific characterization of the mutant. Tests employed for this purpose were the swimming test, air and contact righting responses, open field test, reaching response, elevated platform test and negative geotaxis test. Other vestibular mutants as well as a neurological mutant have also been tested to allow comparison with head bobber. Previously with Richard Smith we found that in the homozygotes no cochlear microphonics or compound action potential could be recorded from the cochlea. We have also described the abnormal structure of the inner ear in adults (from cleared inner ear specimens): the cochlea had a normal gross appearance, but semi-circular canals were absent in all ears studied. From serial sections, the vestibular part of the inner ear was revealed as an extended single cyst, with some development of a sensory epithelium. Reissners membrane was completely collapsed throughout the cochlear duct. The abnormal structure of the inner ear has also been demonstrated in new-born mutants using 3D reconstruction from paraffin wax serial sections. At present, prenatal stages of development are also being examined using this approach to define the abnormal developmental processes that are occurring. As a first stage in identifying the head bobber gene, we are attempting to localize the gene to a specific chromosome. Fluorescence in-situ hybridization (FISH) analysis has revealed the transgene to be located in the telomeric region of a middle sized chromosome. As a second stage to localization of the gene, an intraspecific backcross was set up with CBA and a genome scan using MIT markers is being performed on all 19 autosomes on 33 backcross mice from one set of parents, prior to more detailed mapping on our backcross of over 200 mice. The localization of the gene responsible for this mutation will indicate whether it is a previously undescribed gene or a new mutation of a known locus. This knowledge will give us further insight into the mechanisms responsible for inner ear development. |
