Phenotypes Associated with This Genotype

Genotype
MGI:8377441

• Allelic Composition: Map1b^em1Mgx/Map1b⁺
• Genetic Background: CBA/CaJ-Map1b^em1Mgx

• ♀: phenotype observed in females
• ♂: phenotype observed in males
• N: normal phenotype

hearing/vestibular/ear

abnormal hearing electrophysiology ( J:388508 )

• the waveforms of the outward K+ currents in spiral ganglia neurons are distinct from controls, with peak outward K+ current densities at all test potentials lower than in wild-type

• peak current densities at 60 mV in spiral ganglia neurons account for only 48% of those in wild-type neurons

increased or absent threshold for auditory brainstem response ( J:388508 )

• auditory brainstem response (ABR) thresholds are higher at all ages (4, 8, 16, and 32 weeks) and sound frequencies (8, 12, 24, and 32 kHz) tested

• however, distortion product otoacoustic emissions (DPOAE) is not impaired at all frequencies and at any age tested, indicating that hair cell function is not impaired

abnormal cochlear potential ( J:388508 )

• in whole-cell current clamping recording, single action potentials in spiral ganglia neurons, induced by injected depolarizing currents, are different, showing decreased spike amplitudes (approximately 53.4%), prolonged spike width (about 201.7%), longer spike latency (about 122.5%), and raised threshold of action-potential activation (about 157.1%)

sensorineural hearing loss ( J:388508 )

• mice display late-onset (4 weeks of age) progressive sensorineural hearing loss that is more pronounced in the high frequencies

• however, no apparent morphological abnormality or hair cell loss is seen in the middle turn, apex, or basal turns of cochlea at P30

nervous system

abnormal cranial ganglia morphology ( J:388508 )

• spiral ganglia neurons from the cochlea of P5 mice exhibit shortened neurite lengths

• spiral ganglia neurons show increases in the acetylation levels of alpha-tubulin in the growth cones of axons, indicating altered stability of microtubules

• however, no differences in the density of spiral ganglia neurons are seen at various ages

Mouse Models of Human Disease		DO ID	OMIM ID(s)	Ref(s)
autosomal dominant nonsyndromic deafness 83		DOID:0070609	OMIM:619808	J:388508