Fig. 4. Craniofacial defects of Ednra-null mice. Facial appearances
(A,B) and skeletal structures (C-O) of E18.5 wild-type
(A,C,E,I,J,L,N) and Ednraneo/neo (B,D,F-H,K,M,O) mice are
shown. (A,B) The mutant lower jaw (arrow in B), in contrast to the normal one
(A), appears a mirror image of the upper jaw with duplicated arrays of
vibrissae. (C,D) Lateral and caudal views demonstrate defected and transformed
mandibular (ventral) structures and malformed hyoid fused to the basisphenoid
in mutants (D). (E,F) Mandibular elements including the dentary, goniale and
ectotympanic (E) are mostly lost and replaced by ectopic structures resembling
the maxilla, jugal and palatine, whereas the lower incisor with surrounding
alveolar bone was formed in mutants (F). The zygomatic process of squamosal is
often lost in mutants (arrowhead in F). (G-I) The ectopic bone in the mutant
lower jaw (G) appears a duplication of the ipsilateral maxilla (H), which is
almost identical to the wild-type one (I), except for the distal incisive
alveolus. Broken lines in H and I indicate the margin articulating to the
premaxilla. (J,K) A set of the palatine, pterygoid, ala temporalis and lamina
obturans, the upper jaw elements in normal mice (J), are duplicated and
connected to the ectopic maxilla (mx*) through palatomaxillary-like
articulation in mutants (K). (L,M) In mutants, the malleus and incus are
malformed, giving an ectopic structure extending to the squamosal (arrowhead
in M). The stapes has nearly normal appearance, but is connected to the hyoid
and displaced out of the fenestra ovalis (M). The styloid process was
truncated in mutants (M). (N,O) Unlike the normal hyoid (N), the mutant hyoid
is fused bilaterally to the basisphenoid (arrowhead in O) and connected to the
stapes through an aberrant cartilageous strut (O). amx, alveolus of maxilla;
at, ala temporalis; bh, body of hyoid; bs, basisphenoid; btp, basitrabecular
process; dnt, dentary; etm, ectotympanic; fmx, frontal process of maxilla;
fovl, fenestra ovalis; ghh, greater horn of hyoid; gn, goniale; hy, hyoid; in,
incus; ina, incisive alveolus of dentary; iof, infraorbital foramen; jg,
jugal; lhh, lesser horn of hyoid; LI, lower incisor; lo, lamina obturans; ma,
malleus; mx, maxilla; pl, palatine; pmx, premaxilla, ppmx, palatal process of
maxilla; ptg, pterygoid; sp, styloid process; sq, squamosal; st, stapes; zpmx,
zygomatic process of maxilla; *, ectopic structure.