Fig. 6. Fgfr2, Dlx5, and Twist1 are downstream targets of
TGFß signaling in regulating frontal bone development.
(A) At E13.5, the expression of Fgfr2 is detected in the
frontal primordium (arrow) of the wild type. (B) The expression of
Fgfr2 is reduced in the frontal primordium (arrow) of the
Tgfbr2fl/fl;Wnt1-Cre mutant. (C) At E14.5, frontal
bone matrix begins to form within the frontal primordium of the wild-type
sample. The expression of Fgfr2 is detected throughout osteogenic
progenitor cells in the frontal bone primordium (arrow) and the orbital
surface region of the frontal bone (arrowhead). (D) In the
Tgfbr2fl/fl;Wnt1-Cre mutant, there is virtually no
Fgfr2 expression in the calvarial aspect of the frontal primordium
(arrow), while residual Fgfr2 expression is detected within the
orbital aspect of the frontal bone in the
Tgfbr2fl/fl;Wnt1-Cre mutant sample (arrowhead). (E)
At E13.5, Dlx5 is expressed in the CNC-derived frontal bone
primordium (arrow). (F) Comparable Dlx5 expression is present
in the frontal primordium in the Tgfbr2fl/fl;Wnt1-Cre
mutant (arrow). (G) The frontal bone matrix begins to form at E14.5.
Dlx5 is expressed in both the calvarial (arrow) and the orbital
(arrowhead) aspects of the frontal bone primordium. (H) The
Tgfbr2fl/fl;Wnt1-Cre mutant fails to express Dlx5
in the calvarial aspect of the frontal bone primordium, whereas expression on
the orbital aspect (arrowhead) is normal. (I) No Twist1
expression is detected in the frontal primordium in the wild-type sample.
(J) Elevated Twist1 expression is detected in the frontal bone
primordium (arrow), whereas there is no Twist1 expression in the
orbit region of the frontal bone anlagen (arrowhead) in the
Tgfbr2fl/fl;Wnt1-Cre mutant. Scale bar: 200 µm.