FIGURE 6.

Severe reductions of Fgf8 deform the temporomandibular jaw joint (TMJ). Trichrome stained coronal sections of Fgf8 ^+/+ (WT; left column), Fgf8 ^Neo/Neo (middle column), and Fgf8 ^Δ/Neo (right column) neonatal (P0) skulls. Yellow boxes in upper panels are shown magnified in lower panels. (A, B) In WT, the TMJ has a joint disc [yellow arrow in (B)] below a defined glenoid fossa creating an upper joint cavity. (C, D) The condyle in Fgf8 ^Neo/Neo mice is dysmorphic and rotated vertically and the upper joint cavity is reduced, but an articular disk [yellow arrow in (D)] is still present. (E, F) Fgf8 ^Δ/Neo neonates have a severely reduced glenoid fossa and condylar process, and the joint cavity and articular disc are absent [yellow arrow in (F)]. Red asterisks highlight the condylar process. (G) micro‐CT scans of Fgf8 ^Δ/Neo show the oral cavity opening into the tympanic cavity (white asterisk). Yellow asterisks highlight the malleus. Mouth (m), otic capsule (o). CT, computed tomography