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Fig. 1. XMLC2 is expressed throughout the myocardium of developing Xenopus tadpole. (A) The myosin light chain 2a gene is expressed throughout the heart of the Xenopus tadpole (stage 42). At higher magnification (B), expression is evident in both atrial and ventricular chambers as well as the outflow tract. Ventral views of the heart-forming region reveal XMLC2 expression in bilateral patches of cardiac mesoderm (C) prior to heart tube formation (stage 28). Subsequent formation of a contractile myocardial tube (D; stage 32), looping of the heart tube (E; stage 35) and differentiation of distinct atrial and ventricular chambers (F; stage 42) is clearly visible. Red arrows indicate direction of blood flow (posterior to anterior). (G-J) Transverse sections through the looped heart tube (stage 35) show expression in the myocardial walls of the outflow tract (ot), ventricular (v) and atrial (a) regions and the sinus venosus (sv). |