Fig. 5. Hand1 overexpression promotes extension of the distal OFT, extraneous cardiac looping and impaired LV development. (A-D) Hand1 overexpression in somite-stage matched embryos at E9.5 leads to moderate (B) and significant (C) extension of the distal OFT compared with control littermates (A); quantified in relative units (D), measurements are mean±s.e.m., values of n=9 (A), n=11 (B) and n=5 (C), based on distance depicted by black lines in A-C, ^*P<0.05, ^**P<0.01. The heart tube is extended (E) and displaced ventrally (F; red arrowheads) in overexpression embryos compared with controls. Looping is accentuated and highly convoluted (G) and, in severe cases, the presumptive LV (red asterisk) is small and necrotic (H). co, control; L, left; L/V, left-ventral; oe, overexpression; R, right. Scale bars: 100 µm in C,H; 200 µm in F.