Fig. 4.

HIC2 represses cardiomyocyte expression of fast-twitch skeletal muscle troponins.

a, b. RT-qPCR analysis of gene expression in pooled heart samples. a shows absolute expression (normalised to GAPDH) while b shows the fold change between the genotypes indicated at E13.5. p values indicate results of a one tailed t-test.

c–f. In situ hybridisation showing upregulation of skeletal muscle troponins in mutant hearts at E9.5 in the Mesp1^cre conditional mutant. Arrows indicate tissue showing upregulated expression. Expression of Tnnt3 is limited to the future atrium while Tnni2 is expressed throughout the heart tube.

g–h. Immunostaining to show upregulation of TNNT3 at E13.5. In wildtype embryos (Hic2^FL/FL), TNNT3 expression (red) is seen in skeletal muscle (SM) but not in the heart. In the Nkx2.5^cre conditional mutant, TNNT3 expression is seen in both skeletal muscle and in the atria (A). We do not observe expression in the ventricle (V). DAPI counterstaining (blue) indicates nuclei. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)