International Mammalian Genome Society

The 15th International Mouse Genome Conference (2001)


Verity A. Letts
The Jackson Laboratory
600 Main Street
Bar Harbor
ME 04609

Co-Authors: Letts VA, Tenbrink HK, Wu J, Yu H, Gagnon LH, Bosom KE, Zheng QY, Johnson KR
Institutions: The Jackson Laboratory

We are studying a new mouse mutation, “hard-of-hearing”, that arose spontaneously on the C57BL/6J background.  This mutant was initially identified by its circling behaviour and hearing problems. Auditory brainstem response threshold measurements reveal that the mutant is significantly hearing impaired at five weeks of age and is profoundly deaf by two to three months.  This hearing impairment is fully penetrant, in contrast to the circling defect that is observed in only 60 to 70% of the mutants.

Electron microscopy studies of the mutant cochlea at four weeks of age reveal that the stereocilia are abnormally elongated and fused. The hair cells and Organ of Corti progressively degenerate as the mouse ages, accompanying the onset of deafness in these mutants.

The mutation maps to the middle of mouse Chromosome 9, clearly proximal to Snell’s waltzer (Myo6sv).  A mapping cross between the mutant and CAST/Ei was initiated and over 1,400 F2 animals were genotyped.  Two critical recombinants now define the minimum physical region encompassing the mutation, a distance of 800 kb.  We are investigating the genes within this interval to find the “hard-of-hearing” mutation and study the expression of this gene in the inner ears of control and mutant mice.  The map position of this mouse mutation is homologous with human Chromosome 11q22-q23, the interval including the recessive, nonsyndromic deafness disorder, DFNB24.

(Supported by NIH/NS 32801, NIH/NIDCD 04301 and contract DC62108).

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