Signal intensity maps highlight regions of the <i>Dll4</i> mutant mice that are mis-matched compared to wild-type and heterozygote counterparts.

<p>(A–C) Individual wild-type, heterozygote, and mutant <i>Dll4</i> coronal sections through a 13–16 somite embryo, respectively, are shown while (D) is the average image from the registration pipeline. Because the heart of the <i>Dll4</i>^-/- mouse (C) has not begun to undergo rightward looping, an area of signal increase (red cross-hairs in A-C, and red shading in D) is evident in the average image. This trend continues at the 17–20 somite stage, where sagittal sections through each genotype of the <i>Dll4</i> mice illustrate the lack of any heart structures in the mutants (red cross-hairs in E-G, and blue shading in H). The absence of the dorsal aorta is first noticeable at this time point as well; the red shading in H illustrates that signal exists in the <i>Dll4</i>^-/- mouse, while an empty cavity is present in both the wild-type (E) and heterozygote (F) mouse. The persistence of a stunted, linear heart tube is even more pronounced at the 21–24 somite time point: the red cross-hairs in I-K illustrate the developing ventricle of the wild-type (I) and heterozygote (J) mouse, which is absent in the mutant mouse (K). The absence of the dorsal aorta is still noticeable as well (red shading in L). The colour bar presents the t-statistic of which the minimum corresponds to a FDR threshold of 10%. Scale bar = 500μm.