Fig. 5. Cardiac defects resulting from partial RNAi knockdown of Tbx20. Rendered optical projection tomography (OPT) images of hearts from wild-type (WT; A-C) and RNAi knockdown (a4; D-F) E12.5 mouse embryos. Embryonic stem cells from which knockdown embryos were derived had a 65% reduction in Tbx20 mRNA levels and a 40% reduction in protein levels compared with wild type. (A,D) Surface rendered view. (B,C,E,F) Space-filling images of chamber lumina showing atria in purple (removed in C,F), ventricles in dark red, pulmonary artery in blue and aorta in red. Note the hypoplastic right ventricle and the lack of outflow vessel spiraling in the knockdown heart. Reproduced from Takeuchi et al. (Takeuchi et al., 2005), with permission from Company of Biologists Limited. la, left atrium; lv, left ventricle; ot, outflow tract; ra, right atrium; rv, right ventricle.