The heart is the first functional organ in the vertebrate embryo. In the chick embryo, the heart begins beating at Hamburger and Hamilton [1] stage 10 (approximately 35 hours of a 21-day incubation period). The initially straight heart tube bends and twists into a c-shaped tube before reaching stage 12 (approximately 48 hours incubation). This process, known as c-looping, marks one of the first visible signs of left-right asymmetry in the embryo. Incorrect looping is one cause of congenital heart defects, where significant malformations occur in roughly 1% of human live births [2]. Understanding the mechanisms that drive c-looping could lend insight into the processes causing some of these defects.

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