All Phenotypes Crmp1<em1(IMPC)Mbp> MGI Mouse

hearing/vestibular/ear phenotype ( J:324253 )

N	• mice exhibit normal morphogenesis of cochlear hair cell stereocilia during early development, with no changes in the stereocilia structure of outer or inner hair cells at P5 or P7; both the length and width of the tallest row of inner hair cell (IHC) stereocilia are normal

decreased cochlear outer hair cell number ( J:324253 )

• at 2 months of age, mice show loss of OHCs in the basal turn of the cochlea (corresponding to sensitivity to tones 22-32 kHz), as evidenced by loss of stereociliary bundles

• by 4 months of age, more than 35% of OHCs are lost in the basal turn of the cochlea

• however, no OHC loss is detected in the middle cochlear turn (corresponding to sensitivity to tones 8-22 kHz) at 2 or at 4 months of age

decreased outer hair cell stereocilia number ( J:324253 )

• adult mice exhibit loss of OHC stereociliary bundles in the basal cochlear region that is more severe at 4 months than at 2 months of age

cochlear outer hair cell degeneration ( J:324253 )

• by 4 months of age, more than 35% of OHCs are lost in the basal turn of the cochlea, as determined by myosin-7a immunostaining

increased or absent threshold for auditory brainstem response ( J:324253 )

• at 3 weeks and 2 months of age, ABR thresholds for pure tones are significantly increased at 32 kHz

• by 4 months of age, ABR thresholds for pure tones are significantly increased at high frequencies ranging from 24 to 32 kHz

• however, ABR thresholds for click stimuli are not significantly altered at any age

sensorineural hearing loss ( J:324253 )

• mice exhibit progressive hearing loss at high frequencies, with no detectable differences between sexes