Left-right symmetry-breaking of a cellular flow occurs earlier than node formation
Most animals exhibit external left-right (LR)-symmetric appearance and -asymmetric internal organs. A fundamental question in development is when and how the LR-asymmetry is established for the internal organs, keeping the external body plan bilaterally symmetric.In a study published in Proceedings of the National Academy of Sciences of the United States of America (PNAS), researchers from Kumamoto Univ., Univ. of Miami, and UCSF examined the initiation of LR symmetry breaking during embryonic development, by using chick embryos as a model system (Fig.1 A). The research team utilized fluid dynamics-based biophysical approaches and quantified cellular flows to infer that LR symmetry breaking occurs prior to formation of the node, a LR organizer, which serves as a signaling center for LR patterning-gene programs (Fig.1 B, C).
These results indicate that a tightly regulated program for left-right asymmetry is present in amniote embryos before the formation of a dominant LR signaling center. Hence, this study 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.
Image Caption: (A) Diagram of experimental set up. A dissected chick embryo was cultured and live imaged on a microscope and cellular flow was studied. (B) PIV analysis showing streamlines, indicating an asymmetrical bilateral rotation of the cellular flow during primitive streak extension. (C) Speed plot, indicating the speed of the cellular flow during primitive streak extension. The speed was dominant on the right-side.
Reference
Reference
| Authors |
Rieko Asai, Shubham Sinha, Vivek N. Prakash, and Takashi Mikawa |
| Title of original paper |
Bilateral cellular flows display asymmetry prior to left–right organizer formation in amniote gastrulation |
| Journal | PNAS |
| DOI | 10.1073/pnas.2414860122 |