Sequence and Expression Analysis of <i>cfk</i>

<div><p>(A) <i>cfk</i> encodes a sarcomeric actin highly homologous to zebrafish α-cardiac and α-skeletal actins. Cfk differs from zebrafish α-cardiac actin at six residues and from zebrafish α-skeletal actin at four residues, but from zebrafish β-actin at 28 residues. Residues in red are those that differ from Cfk. Dots above the sequence indicate residues that universally distinguish sarcomeric from cytoplasmic actins. The arrow at R177 indicates the location of histidine in Cfk^s11.</p> <p>(B) The arginine at position 177 is universally conserved in all actin proteins examined.</p> <p>(C and D) <i>cfk</i> is expressed in the myocardium during development. In (C), whole-mount in situ hybridization on a cmlc2::GFP embryo at 36 hpf shows that <i>cfk</i> is expressed throughout the AP extent of the heart tube. Blue staining indicates areas of <i>cfk</i> expression; green is the region of cmlc2 expression. The red arrow indicates the heart tube. In (D), a plastic section of stained embryo shows <i>cfk</i> expression in the myocardium of the heart (blue arrow), but not in the endocardial cells (red arrow). From the onset of its expression in the heart region (around the 16-somite stage), <i>cfk</i> does not appear to be expressed in endothelial and endocardial cells. Weak <i>cfk</i> expression is also seen in the somites (data not shown).</p>