The evolution and conservation of left-right patterning mechanisms.
Morphological asymmetry is a common feature of animal body plans, from shell coiling in snails to organ placement in humans. The signaling protein Nodal is key for determining this laterality. Many vertebrates, including humans, use cilia for breaking symmetry during embryonic development: rotating cilia produce a leftward flow of extracellular fluids that induces the asymmetric expression of Nodal. By contrast, Nodal asymmetry can be induced flow-independently in invertebrates. Here, we ask when and why flow evolved. We propose that flow was present at the base of the deuterostomes and that it is required to maintain organ asymmetry in otherwise perfectly bilaterally symmetrical vertebrates.
Institute of Zoology, University of Hohenheim, 70593 Stuttgart, Germany.
Martin
M
Blum
Kerstin
K
Feistel
Thomas
T
Thumberger
Axel
A
Schweickert
D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning; D006801:Humans; D038081:Organogenesis; D014714:Vertebrates / Q000196:embryology
Cilia; Evolution; Left-right asymmetry; Left-right organizer; Leftward flow