mortality/aging
• homozygotes occasionally survive to E10.5, with a few surviving up to E13.5
|
hearing/vestibular/ear
• at E13.5, homozygotes exhibit a variable degree of otocyst formation, with 2 of 4 mutants found arrested at an earlier otocyst stage (E10.5)
• however, all sensory epithelia can be tentatively identified in remaining two (least severe) cases
|
• at E11.5, homozygotes display a much smaller invaginating otocyst relative to heterozygotes; however, the ectodermal patch of tissue anterior to the otocyst appears larger
|
• inner ear morphogenesis and growth is severely inhibited after initial otic vesicle formation
|
• at E13.5, the entire inner ear appears as an elongated cyst, with a single extension of the endolymphatic duct observed in more developmentally advanced mutants
|
• homozygotes display a severe reduction of cochlear sensory neuron formation
|
• at E13.5, developmentally advanced homozygotes display a cochlea with a single ventral extension rather than one turn, suggesting reduced cochlear outgrowth
|
• at E13.5, the common crus of the anterior and posterior canal is absent
|
• at E13.5, the three semicircular canals are absent
|
• at E13.5, no utricular recess is formed
|
• at E13.5, no saccular recess is formed
|
• at E13.5, less severely affected homozygotes display a single recess coming out of the otocyst, which is interpreted as the endolymphatic duct
|
nervous system
• homozygotes exhibit abnormal axonal navigation of the inner ear efferent neurons
|
• homozygotes display aberrant inner ear efferent axonal projections, such as projections of fibers through the facial branchial motor nerve root, and caudal extension of efferent axons along the floor plate midline into r5 and occasionally into r6, not seen in wild-type littermates
|
cellular
• homozygotes exhibit abnormal axonal navigation of the inner ear efferent neurons
|
growth/size/body
• at E13.5, the entire inner ear appears as an elongated cyst, with a single extension of the endolymphatic duct observed in more developmentally advanced mutants
|