Figure 1.
Morphological and histological comparisons of the middle and inner ears.
(A) The bullae of Fgf mice (bottom row) appear white and cloudy with less structural refinement than both Fgf
(top row) and Fgf
mice (middle row), indicating incomplete ossification. (B) The auditory ossicles are dysplastic in Fgf
mice. (C) H&E stained, paraffin sections demonstrate increased vascularization of the bony labyrinth in Fgf
mice (arrowheads). (D) The highly-organized laminar structure of the otic capsule, bordering the spiral ligament, is lost in the Fgf
genotype. Lines in A and B are orienting lines from the microscope objective.
Figure 2.
Morphological comparisons of the otic capsule from (A) Fgf, (B) Fgf
and (C) Fgf
mice.
All genotypes appear similar but the Fgf cochlea is slightly smaller and whiter. Black lines are orienting lines from the microscope objective.
Figure 3.
Mid-modiolar cochlear sections from Fgf (left column) and Fgf
mice (right column).
(A) Neural populations and gross anatomical structure appear normal in Fgf mice. (B) The stria vascularis (StVas), spiral ligament (SpLig), spiral limbus (SpLim), tectorial membrane (TM) and Reissner's membrane (RM) are similar to Fgf
mice. (C) Inner hair cells (IHC), Outer hair cells (OHC), supporting cells (SC) and basilar membrane (BM) are morphologically normal. Sections were embedded in araldite and osmium stained.
Figure 4.
FGF23 immunohistochemistry in Fgf and Fgf
mice.
(A) Specific staining was observed in the cells of the spiral ligament, stria vascularis, Organ of Corti, spiral limbus and within the spiral ganglion neuronal cell bodies in Fgf mice (similar patterns were observed in Fgf
mice). Inset images are zoomed in views of the boxed regions. (B) No immunoreactivity was observed in Fgf
mice. (C) Similarly, no staining was observed in negative controls, from Fgf
mice which were processed without the primary antibody.
Figure 5.
2D and 3D CT reconstructions of bullae from Fgf
and Fgf
mice.
Each row contains reconstructions from one ear (top row: Fgf, bottom row: Fgf
). (A) The otic capsule and bulla show loss of structural refinement and decreased density (arrowheads). (B) In Fgf
mice the footplate of the stapes demonstrate thickening (arrowheads). (C) The incus and incudomalleal joint are dysplastic (arrowheads) and the mastoid is under-pneumatized (asterisks). (D) The borders of 3D reconstructed Fgf
ossicles are sharp and well-defined while those of Fgf
ossicles are blurry due to poor contrast with surroundings, resulting from decreased bone density in the mutant. Fgf
ossicles demonstrate reduced structural refinement, particularly in the malleus and incus.
Figure 6.
Auditory measurements from Fgf mutant mice.
(A) ABR and (B) DPOAE thresholds demonstrate profound hearing loss at all frequencies in Fgf mice, and moderate hearing loss at high frequencies in Fgf
mice. (C) ABR wave I amplitudes appear slightly depressed in Fgf
mice but are not statistically differentiable (except at 32 kHz where threshold differences impact magnitude
). ABR amplitudes in Fgf
mice are significantly reduced compared to the other genotypes
. (D) Threshold adjusted ABR wave I latency measurements demonstrate significant increases in latency in both Fgf
and Fgf
genotypes when compared to Fgf
littermates
. Error bars present standard error of the mean.