Fig. 2. Gfi1 wild-type expression in the sensory epithelia of the inner ear. mRNA in situ hybridization using a specific antisense probe derived from the 3' UTR of Gfi1 and immunohistochemistry using a Gfi1-specific antibody. For in situ hybridization, positive cells are purple, and for immunohistochemistry, positive cells are brown and counterstained with Hematoxylin (purple). (A) Sagittal section of E12.5 embryo. Gfi1 is expressed in the otic vesicle (OV) and several ganglia including the vestibulo-cochlear ganglia (VIII). (B) Sagittal section of E14.5 ear. Gfi1 is expressed in the saccule (S) and utricle (U), but high levels of expression are not yet visible in the cochlea (Co). (C) Sagittal section of E16.5 ear. Gfi1 is expressed in the saccule (S), utricle (U) and cochlea (Co). An arrow indicates the hair cells in the organ of Corti. (D) Sagittal section of E18.5 cochlea. High expression levels of Gfi1 mRNA can be seen in the hair cells. The inner hair cell is indicated by a red arrow and the outer hair cells by green arrows. Lower levels of expression can be seen in the cochlear ganglia (asterisk). (E) Sagittal section of E14.5 ear. Gfi1 protein is expressed in the saccule (S) and utricle (U). (F) Sagittal section of E18.5 cochlea. High expression levels of Gfi1 protein can be seen in the hair cells. The inner hair cell is indicated by a red arrow and the outer hair cells by green arrows.