Figure 6. Alteration of FGF, BMP and Notch Signaling in Pitx2 Mutants.

RNA in situ hybridization on cryostat sections revealed altered Fgf8 (A–C), Fgf3 (E–G), Notch2 (I–K) and Bmp4 (M–O) expression in E10.5 Pitx2 control (wild type and heterozygote) and mutant mice. The Fgf8 expression in 3^rd and 4^th BA ectoderm was decreased in mutants compared to control embryos (C). Fgf3 expression levels were reduced in the 2^nd – 6^th BA mutants (G). Notch2 expression levels, detected in the 3^rd and 4^th BA in wild type (I) and heterozygote (J), were barely detectable in 3^rd and 4^th BA in mutants (K). No Bmp4 expression was detected in the OT mesenchymal cushions (area inside the black dotted line) in mutants (O) compare to the control (M, N). Thinner OT wall (between red and black dotted line) was consistently observed in Pitx2 mutants (O). Quantitative PCR assay indicated the significantly decreased mRNA expression levels of Fgf8 (D), Fgf3 (H), Notch2 (L) and Bmp4 (P) at E10.5 BA (D, H, L) and heart (P) biopsies, respectively.