Mouse Genome Informatics
hm
    Myo7ash1/Myo7ash1
involves: BALB
Key:
phenotype observed in females WTSI Wellcome Trust Sanger Institute
phenotype observed in males EuPh Europhenome
N normal phenotype
       

Cochlear hair cell abnormalities in Myo7aHdb/Myo7a+, Myo7aHdb/Myo7a+ Myo7a4626SB/Myo7a+, and Myo7ash1/Myo7ash1 mice

behavior/neurological
• when placed on a cold concrete floor mice rarely travel more than 6 feet and this distance is covered in short jerky stops and starts
• water consumption is increased compared to in wild-type mice
• by 22 days
• while mice can swim at a young age their lose their ability to do so in the second month of age
• mice display a nervous head movement characterized by rapid, successive jerking of the head upwards accompanied by sniffing and twitching of the vibrissae
• however, mice can cease their head jerking for periods of time and appear normal
• 14% of mice exhibit a moderate circling behavior with a tendency to circle counter-clockwise (J:15554)

growth/size/body

hearing/vestibular/ear
• formation of fluid spaces is delayed with no tunnel spaces evident until day 12 and intercellular spaces between hair cells not apparent until day 21 (J:14846)
• maturation of the organ of Corti is delayed as indicated by the presence of round or ovoid shaped outer hair cells at day 10 and deformation of Nuel's spaces and the tunnel of Corti (J:28477)
• by day 18 Nuel's spaces have not formed and the tectorial membrane remains attached to the reticular lamina (J:28477)
• the intercellular spaces that appear between hair cells occur at day 21 instead of day 10 as in wild-type mice
• efferent nerve innervation does not occur until day 12 compared to day 10 in wild-type mice and only a small number can be found
• mitochondrial swelling and vesicle formation are observed in both afferent and efferent nerve endings as mice age
• no auditory hair cells can be found between the level of the reticular lamina and the tectorial membrane
• efferent arrival at the outer hair cell is delayed
• however, efferent nerve supply to the inner hair cells is normal if not over-abundant
• degeneration of the hair cells occurs at 7 weeks of age (J:13130)
• hair cells are absent in adult mice (J:14846)
• hair cell degeneration is apparent as early as 12 days (J:14846)
• by 4 months (J:14858)
• by 4 months, the stria vascularis is atrophic
• cochlear potential is delayed by one day compared to in wild-type mice and mice do not respond to the full range of frequencies
• eighth nerve activity N1 and N2 is delayed and never obtain the amplitude that they do in wild-type mice
• by day 22, eighth nerve action potential has disappeared
• by 22 days hearing is lost (J:14858)
• mice become deaf at around 22 to 30 days (J:15554)

reproductive system
• males tend towards infertility because of their nervous condition (J:15554)

nervous system
• the intercellular spaces that appear between hair cells occur at day 21 instead of day 10 as in wild-type mice
• efferent nerve innervation does not occur until day 12 compared to day 10 in wild-type mice and only a small number can be found
• mitochondrial swelling and vesicle formation are observed in both afferent and efferent nerve endings as mice age
• no auditory hair cells can be found between the level of the reticular lamina and the tectorial membrane
• efferent arrival at the outer hair cell is delayed
• however, efferent nerve supply to the inner hair cells is normal if not over-abundant
• degeneration of the hair cells occurs at 7 weeks of age (J:13130)
• hair cells are absent in adult mice (J:14846)
• hair cell degeneration is apparent as early as 12 days (J:14846)
• by 4 months (J:14858)
• mice exhibit increases fibrous astrocytes in the medial vestibular nucleus
• after 2 months (J:13130)
• spiral ganglia formation is delayed and fewer spiral ganglia are present (J:14846)
• at 22 days, mice have few spiral ganglia that are irregular, small, show more chromatic stiplings and minimal vascuolization (J:14858)
• by 4 months, ganglion cells have atrophied (J:14858)
• by day 10, spiral ganglion cells are unmyelinated and contain a large number of swollen mitochondria, dense bodies and an expanse of smooth endoplasmic reticulum (J:28477)

Mouse Models of Human Disease
OMIM IDRef(s)
Usher Syndrome, Type I; USH1 276900 J:5133 , J:15554