Fig. 4. Hand1 overexpression promotes extension of the distal OFT, extraneous cardiac looping and impaired LV development. Rendered optical projection tomography of embryos at E9.5 (pericardium removed), viewed from left, ventral and right aspects, in control embryos (containing just the responder transgene; A-C), in Hand1-overexpressing embryos with a moderate phenotype (D-F) or in severe phenotype embryos (G-I). Frontal sections through the hearts of control (J) and moderate Hand1-overexpressing embryos (K) in the planes depicted in B and F, respectively. Sagittal sections through the hearts of control (L) and severe phenotype Hand1-overexpressing embryos (M) in the planes depicted in C and H, respectively. co, control; lv, left ventricle; oe, overexpression; oft, outflow tract. Scale bar: 100 µm in A.