Abnormalities of the stapedio-vestibular (S–V) joint and cochlear bony capsule in Pou3f4Cre/Y males.

(A–D) Views of the middle ear medial wall/cochlear bony capsule from control (A,C) and Pou3f4Cre/Y temporal bones (B,D) at 16 weeks of age. Soft tissue and bony structures, including the stapes head and crura, are dissected away for unobstructed views of the stapes footplate (fp) in oval window (ow) and cochlear bony capsule. rw, round window. (C,D) are magnified views of the fooplate/oval window in (A,B), respectively. Brackets in (D) highlight disarticulation at a severely affected mutant S–V joint with hypoplastic footplate. Asterisk highlights artifactual fracture of the footplate during dissection. Dotted line in (A) shows the course of the VIIth nerve within the facial canal. Arrows in (B) highlight translucence of the thin mutant cochlear bony capsule compared to wild-type; arrowheads in (B) highlight visibility of strial blood vessels and melanocytes through the mutant bony capsule. Axes in (B) apply to (A–D). (E, F, F′) Wild-type (E) and mutant (F, F′) S–V joint in histological section stained for elastic fibers (black), collagen (light pink), and nuclei. (F) corresponds to a bracketed regions of disarticulation in (D); (F′) corresponds to a region of mutant S–V joint where footplate and oval window are more closely apposed. Corresponding photos of wild-type and mutant are shown to scale.