Left-Right asymmetry of embryonic cell movement

What is it about?

Most animals exhibit external left-right (LR) symmetric appearance about the midline. However, this external bilateral symmetry switches to asymmetry in internal organizations of organs. Here, using chick embryos as a model system, we examined the initiation of LR symmetry breaking during embryonic development. Our biophysical approaches to quantify cellular flows inferred that LR symmetry breaking occurs before the formation of the node, a LR organizer, which serves as a signaling center for LR patterning-gene programs. Our work demonstrates that quantitative biophysical parameters can help unravel the initiation of LR symmetry breaking, suggesting an involvement of physical mechanisms in this critical biological patterning process.

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Why is it important?

A fundamental question in development is how the LR-asymmetry is established for internal organs, keeping the external body plan bilaterally symmetric. Defects in LR-asymmetry for internal organs in humans could cause serious clinical problems. Although the bilaterally symmetric body plan is ubiquitously observed in the animal kingdom, it remains elusive how and when symmetry breaking for internal organ patterning is programmed. Our work quantitatively demonstrates that a tightly controlled program for left-right asymmetry is displayed in amniote embryos much before a dominant LR signaling center formation.

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