Low-frequency-specific hearing loss in 4-wk-old Fst cKO mutants. (A–C) ABR analyses of 4-wk-old Fstlox/lox and Pax2-Cre; Fstlox/lox mice. ABR thresholds of Fstlox/lox and Pax2-Cre; Fstlox/lox mice to click stimuli and individual frequencies (A). I/O function analyses of wave I amplitudes from the ABRs to low (6 kHz) and high (18 kHz) frequencies (B, C). (D–F ) DPOAE analyses of 4-wk-old Fstlox/lox and Pax2-Cre; Fstlox/lox mice. 2f1-f2 DPOAE thresholds of Fstlox/lox and Pax2-Cre; Fstlox/lox mice (D). DPOAE I/O function analyses at 6 kHz and 18 kHz (E, F ). Data are presented as means ± SE. Statistical comparisons were determined via two-way ANOVA with Bonferroni corrections for multiple comparisons (n.s., non-significant, *P < 0.05, **P < 0.01, and ***P < 0.001).