Effects Of A Teratogenic Dose Of Retinoic Acid On Foxc2 Expression In Mouse Embryo

Mouse Foxc2 (Forkhead Box c2), a member of the winged helix transcription factors super family with DNA-binding domains,is evolutionarily highly conserved. Foxc2 plays a key role in normal embryo development. Foxc2 gene deleted mice fetuses most dead at prenatal,which present as serious cardiovascular defection,and abnormal development of axial skeletons, kidneys,and eyes. Human FOXC2 mutation is associated with several hereditary and metabolic diseases. Retinoic acid signal pathway plays a key role in embryo development,cell proliferation and differentiation,and organ maintenance. Either deficiency or excess of retinoic acid could result in malformation.Objective Based on the effects on same tissues and organs of Foxc2 and Retinoic acid, we studied whether the Retinoic acid at teratogenic dose effects the expression of Foxc2 and regulatory mechanism of Foxc2 in embryo development.Methods Pregnant mice were randomly divided into control group and experimental group. Mice in experimental group were treated with all-trans-retinoic acid 60mg/kg body weight once by intragastric administration. We detected the differences in expressional pattern of Foxc2 in embryo heart, eye,skeleton,and inner ear between control and experimental group from E11.5 to E16.5 by Immunohistochemistry , and analysis the expressional level differences between the two groups of the same embryo age and in the same tissue. Foxc2 expressional level was represent by the optical density.Results Foxc2 expressed extensively in the mouse embryo. Foxc2 expressed in the endomembrane of atrium cordis and conus cordis and blood vessel and mesenchyme surrounding the heart; From E13.5 to E16.5, Foxc2 expressed significantly higher in control group than in experimental group (P<0.05). Foxc2 expressed in endothelial cells and mesenchyme of cornea and eyelid, and the mesenchyme of the posterior part of caliculus ophthalmicus, but only in endothelial cells and mesenchyme of cornea and eyelid after catacleisis; E13.5-E15.5, the expression of Foxc2 showed a tendency of up-regulation and showed a peaking at E16.5; at E13.5, E15.5 and E16.5, Foxc2 expressed significantly higher in control group than in experimental group (P<0.05). Foxc2 expressed extensively in the bone, including vertebrae, costal bone and appendicular skeleton; the expression of Foxc2 increased and sequentially decreased in the embryo of control group, and showed a peaking at E14.5; at E13.5 and E15.5, Foxc2 expressed significantly higher in the vertebrae of control group than experimental group (P<0.05); at E14.5, Foxc2 also expressed higher in the control group than experimental group, but not significantly. Foxc2 expressed in the acoustic capsule,cochlea,cartilage capsule and surrounding mesenchyme of inner ear; the expression intensity of Foxc2 did not change greatly with increase of age; E12.5-E15.5, Foxc2 expressed significantly lower in control group than in experimental group (P<0.05), contrary to the expression in other tissue.Conclusions Foxc2 is very important in the normal early development of hearty, bone, eye and inner ear in mouse embryo, and Foxc2 protein expression level had a peak at E13.5 and E14.5; Teratogenic dose of Retinoic acid could inhibit Foxc2 expression in heart, bone and eye of mouse embryo, and inhibition cycle of Retinoic acid is coincident with the expression cycle of Foxc2; Foxc2 strongly expressed in cochlea, cartilage capsule and surrounding mesenchyme in the inner ear, Retinoic acid at teratogenic dose could promote the expression of Foxc2.