Extended Data Fig. 5: Conditional ablation of Insm1 in hair cells using Gfi1-Cre causes no hearing impairment, and results in only very few oc-IHCs.
From: Trans-differentiation of outer hair cells into inner hair cells in the absence of INSM1
We generated a conditional knockout of Insm1 in hair cells using Gfi1-Cre, in which the expression of cre recombinase coincided with that of Insm1. a, b, Hearing thresholds determined by ABRs (a) and DPOAEs (b) of Gfi1Cre/+;Insm1F/F mice at age P30–P35 (black traces; n = 6, 4 males and 2 females) and control littermates (red traces; n = 6; 1 Insm1F/F, 1 Insm1F/+ and 4 Gfi1Cre/+;Insm1F/+; 4 males and 2 females). There is no significant difference in ABR and DPOAE thresholds at any frequency tested between Gfi1Cre/+;Insm1F/F mice and their control littermates. c, Immunohistochemistry in whole-mount organs of Corti from mid-cochlear positions of P34 mice tested for hearing in a, b revealed that Gfi1Cre/+;Insm1F/F mice had normal IHCs expressing high levels of calmodulin. However, very few oc-HCs also expressed calmodulin at high levels, oncomodulin at low levels, and had a round, flask shape similar to that of IHCs (0.78%; 5/526 OHCs from 2 mice). Because in these Gfi1Cre/+;Insm1F/F mice the onset of Cre recombinase expression coincides with that of Insm1 (E15.5–E17.5)43, their nascent OHCs will express Insm1 for at least several hours. This result indicates that brief expression of Insm1 is sufficient to promote proper OHC differentiation. Scale bars, 10 µm. Biological replicates were used for all experiments and similar immunohistochemistry results obtained from three or more mice per genotype.
