Figure 2.

R26r reporter analysis of Noggin overexpressing lineages. (A–D): Left sided views of wholemount X-gal staining of control Nfatc1^Cre/R26r (A,C) and mutant pMes-Noggin/Nfatc1^Cre/R26r (B,D) embryos at E9.5 (A,B) and E11 (B,D) developmental stages, showing that Cre recombinase-mediated lacZ expression (blue) is restricted to the heart. Note lacZ staining reveals no obvious differences between control and Nog^End mutants hearts, although the E11 Nog^End mutant's heart is smaller; (E,F): Isolated control and Nog^End E12 hearts viewed frontally, reveals that Nfatc1^Cre/R26r–mediated lacZ reporter expression is still present in mutant heart (F) but that it is highly dysmorphic, misshapen and undersized; (G–O): Representative matched views of control E10 (G), E10.5 (I,K), E11 (M,N) and Nog^End mutant E10 (H), E10.5 (J,L), E11 (O) serial sections X-gal stained and counterstained with eosin. Transverse sections of E10 control (G) and Nog^End hearts (H) showed that lacZ expression was similarly localized in the endocardium and endocardial-derived cushion mesenchymal cells at the atrioventricular canals. E10.5 lacZ stained sagittal heart sections revealed that Nog^End mutant atrioventricular cushion is reduced in cellularity (arrow in (L)) when compared to control, littermate (K); Additionally, the Nog^End endocardium is detached from the underlying mutant trabeculae (J,L); Transverse sections of the X-gal stained E11 control (M,N) and mutant (O) hearts illustrates the hypoplastic endocardially-derived OFT (indicated via *) and atrioventricular cushions (arrow in (O)), the reduced trabeculae and detached endocardial lining; Note however, that Nog^End neural-crest-derived OFT cushions are grossly normal in cellularity (O); Scale bars: (A–F) = 100 μm; (G–L) = 20 μm; (M–O) = 100 μm. Abbreviations: la, left atria; lv, left ventricle; oft, outflow tract; rv, right ventricle.