Phenotypes Associated with This Genotype

Genotype
MGI:2173304

• Allelic Composition: Hmx2^tm1Tlu/Hmx2^tm1Tlu
• Genetic Background: involves: 129S1/Sv * 129X1/SvJ * C57BL/6J

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

behavior/neurological

head tilt ( J:73069 )

• approximately 65% of homozygous mutant mice display head tilting

hyperactivity ( J:73069 )

• approximately 65% of homozygous mutant mice display hyperactivity

circling ( J:73069 )

• approximately 65% of homozygous mutant mice display circling activity

hearing/vestibular/ear

abnormal ear development ( J:73069 )

• the mutant otocyst exhibits altered expression of specific inner ear markers in the presumptive sensory epithelium, as well as ectopic gene activation in the prospective fusion plate, indicating a significant alteration in cell fate in the otic epithelium of the pars superior

• as a result of altered cell fate, the otic epithelium fails to communicate properly with the periotic mesenchyme, and inner ear morphogenesis is disrupted

abnormal inner ear morphology ( J:73069 )

abnormal inner ear canal fusion ( J:73069 )

• at E11.5, a reduced rate of cell division is detected in the otic epithelium as well as in the adjacent periotic mesenchyme; at this stage, thinning of the epithelial layer in specific regions of the otic vesicle fails to occur, suggesting that no region in the mutant otocyst has become competent to form a fusion plate

• at E13.5, the presence of a thinned epithelial layer and its detachment from the underlying basement membrane suggest a potential delayed initiation of fusion plate formation; however, the eventual fusion of the apposing walls of the otocyst to form a semicircular duct never takes place

abnormal crista ampullaris morphology ( J:73069 )

• homozygous mutant mice display significant loss of the three cristae: also, a putative crista marker is present at E10.5, but disappears by E11.5, suggesting that the cristae might be specified initially but fail to develop properly

absent semicircular canals ( J:73069 )

• as early as E13.5, approximately 70% of homozygous mutant embryos exhibit severe dysgenesis of all three semicircular ducts; the remaining 30% display variable defects in the vestibule between different individuals, and even between the membranous labyrinths of the same homozygous mutant embryos

abnormal inner ear vestibule morphology ( J:73069 )

• homozygous mutant mice display persistence of the primordial vestibular diverticula, a fused utriculosaccular space in which a common macula is formed, as well as a severe loss of epithelial cells (both sensory and nonsensory) in the developing vestibule

nervous system

nervous system phenotype ( J:73069 )

N • no defects are observed in the CNS, as shown by the behavior, beta-galactosidase activity and histology of homozygous mutant mice and embryos