Table 2.

Comparison of results obtained from various Cx26 and Cx30 mutant mouse models

Animal models	Cx30 null	cCx26 null	Cx26R75W-Kudo	Cx26R75W-Maeda
Reference of the first report	(Teubner et al., 2003)	(Cohen-Salmon et al., 2002)	(Kudo et al., 2003)	(Maeda et al., 2007)
Approach used	Targeted replacement of Gjb6 by LacZ/neo	Gjb2 is flanked by loxP. Excision of Gjb2 by otogelin-driven Cre expression from a BAC	hCx26 R75W is expressed under universal CAG promoter	pGJB2R75W-eGFP plasmid (CMV promoter) delivered by lipofection applied to the round window membrane
Time and location of Cx deletion	Germline deletion of Gjb6	Gjb2 presumably is deleted at E10 in sensory epithelium of the cochlea	The dominant- negative Gjb2 mutant is presumably expressed before the first meiotic division. Detailed cellular pattern of expression is unknown	The dominant- negative Gjb2 mutant is expressed in adult cochlea. Many cochlear cells expressed the mutant Cx as detected by the GFP immunolabeling
Inner and outer hair cell loss	Hair cell losses begin at the third week postnatally. and increase gradually with age. Outer hair cells are affected first and more severely	Gross morphology of inner hair cells appears to be normal in most animals. Outer hair cell loss starts at P15. The two most internal rows are affected first	Inner hair cells are present but show changed shape. Outer hair cells are present at P14 but show shape changes and they degenerated at the seventh week	No hair cell loss and hearing loss is transient. Auditory sensitivities recover in 5 days after introducing mutant
Vestibular morphology	Vestibular hair cell loss specifically in the saccule is observed (Qu et al., 2007)	Normal up at least to P60	Normal by functional assessment	No data reported
Supporting cell loss	Not degenerated	Initial damage observed at P15	Initial damage observed at P14	Not affected
Is there SG neuron loss?	No description provided.	No SG neuron degeneration observed	Degeneration of SG neurons in basal turn noted at seventh week postnatally
Is the opening of the tunnel of Corti affected?	No	No	Yes (Inoshita et al., 2008)
Hearing threshold elevation	At P17–18, click ABR threshold elevation is about is 50 dB. Adult mice show no ABRs at >100 dB	About 30 dB elevation at the most sensitive frequencies on average.	Greater than 100 dB threshold elevation	About 15–20 dB threshold elevation as assessed by click ABR
EP value	At P13/P14: 0±4 vs. 74±9mV in control mice. In adults: 3±3 vs. 148±15 mV in controls	At P12–13: 56±12 vs. 58±12mV in control mice. In adults: 38±14 vs. 110±12mV in controls	In adults: 87±2.5 vs. 97.4±7.1 mV in control mice
Endolymphatic K+ concentration	At P13/P14: 100±39 vs. 102±24 mM in control mice. In adults: 44±19 vs. 148±15mM	In adult: 85±21 vs. 153±7mM in the control mice
Morphology changes in the organ of Corti, spiral limbus, stria vascularis, firbrocytes in the lateral wall	No gross morphological changes in stria vascularis, lateral wall is observed. No displacement of Reissner’s membrane observed	Disruption of the reticular lamina, missing of some interdental cells. Gross cochlea structure appear to be normal	No gross changes in gross cochlear morphology observed. No opening of the tunnel of Corti. The Nuel’s space is absent. Microtubule abnormality in Inner pillar cells.