All Phenotypes Adgrv1<tm1Msat> MGI Mouse

increased susceptibility to induced morbidity/mortality ( J:95518 )

• 26% of homozygotes died following tonic convulsion

• from P21 to P27, 95% of homozygotes exhibited wild running (compared to 10% in wild-type) and 68% exhibited convulsions during the first 20 seconds of auditory stimulation, indicating susceptibility to audiogenic seizures

audiogenic seizures ( J:95518 )

• from P21 to P27, 95% of homozygotes exhibited wild running (compared to 10% in wild-type) and 68% exhibited convulsions during the first 20 seconds of auditory stimulation, indicating susceptibility to audiogenic seizures

abnormal cochlear hair cell stereociliary bundle morphology ( J:122415 )

• homozygotes show a gradually increasing disorganization of hair bundles from the cochlear base to apex, starting from P4 at the base; however, a typical staircase pattern shaped by three rows of stereocilia is observed

• at P6, both usherin and vezatin are no longer present at the base of the hair bundle (as in wild-type mice) but remain in the kinocilium both in OHCs and IHCs

• at P6, whirlin is detected only in the apical end of stereocilia and supernumerary neural edge microvilli instead of both the base and apical end of stereocilia as observed in wild-type mice

• at P7, a dramatic increase in adenylate cyclase 6 labeling is detected in both OHC and IHC stereocilia, extending along the entire length of stereocilia instead of being restricted to the stereocilial base

• in addition, the long cadherin 23 class A isoforms are absent, with the N1 (extracellular) epitope detected at P0 but not at P6, while the Ela3 (both intracellular and extracellular) epitope is abnormally preserved until P17

absent cochlear hair bundle ankle links ( J:122415 )

• at P6, ankle links are absent from both cochlear inner and outer hair cell stereociliary bundles

• in contrast, other lateral links are still present

abnormal inner hair cell stereociliary bundle morphology ( J:122415 )

• at P6, IHCs exhibit asymmetrical instead of symmetrical arch-shaped hair bundles

• notably, peripheral microvilli at the neural edge side fail to regress in most IHCs, whereas these microvilli normally disappear before P6 in wild-type mice

• in addition, peripheral microvilli undergo a stereocilia-like maturation as they organize themselves in one or two rows, conferring a circular shape to the hair bundle, their stereocilia base becomes sharpened, and they exhibit an increased phalloidin labeling at P11, indicating a progressive increase of actin filament content

abnormal outer hair cell stereociliary bundle morphology ( J:122415 )

• at P6, most OHCs display U-shaped or rounded hair bundles, instead of the expected V shape seen in wild-type mice

• occasionally, peripheral microvilli at the neural edge side fail to regress in OHCs, whereas these microvilli normally disappear before P6 in wild-type mice

abnormal cochlear outer hair cell physiology ( J:122415 )

• at P7, mechanoelectrical transduction (MET) currents elicited by mechanical stimulations of the hair bundle in the stimulatory direction are impaired in OHCs, with a significant shift of the relative Po-displacement curve toward larger displacements and a decrease in the slope, indicating reduced sensitivity of the hair bundle to mechanical stimulation

abnormal hair cell mechanoelectric transduction ( J:122415 )

• at P7, MET currents evoked by displacements of the hair bundle toward the tallest stereocilia (i.e., in the excitatory direction) are decreased in OHCs but not in IHCs

• surprisingly, in both OHCs and IHCs, stimulation of the hair bundle in the opposite (inhibitory) direction results in significant MET transduction currents which are reversibly abolished with dihydrostreptomycin, an MET channel blocker