Dynamics of Peripherin (PRPH) and class III β-Tubulin (TUBB3) expression in the human fetal spiral ganglion. (A-E) Basal turn spiral ganglion immunostained for PRPH (green) and TUBB3 (red) at (A) W10.4 (week 10 and 4 days), (B) W12, (C) W15 and (D) W18. (E) Magnification of the basal turn spiral ganglion marked with a white arrow in (D). Cell nuclei were visualized with DAPI (blue). White arrow, PRPH-positive spiral ganglion neurons; black arrow, PRPH-negative and TUBB3-positive nerve fiber bundles. Scale bars = 20 μm.