Fig. 6.

Cardiac expression of Tbx2, Tbx5, and Tbx20. The in situ hybridization patterns of Tbx2, Tbx5, and Tbx20 in the forming cardiac chambers were examined in transverse sections through the tadpole heart after looping. a: Tbx2 expression was seen in the myocardium of both the atrial (am) and ventricular (vm) regions of the looped heart at stage 36. b: Expression of Tbx5 was restricted primarily to the developing ventricular myocardium at stage 38. c: In contrast to Tbx5, high levels of Tbx20 expression were seen in the atrial region but not in the ventricle (stage 40). Original magnification, ×100.