title: Two rotating cilia in the node cavity are sufficient to break left-right symmetry in the mouse embryo.
abstract: Determination of left-right asymmetry in mouse embryos is achieved by a leftward fluid flow (nodal flow) in the node cavity that is generated by clockwise rotational movement of 200-300 cilia in the node. The precise action of nodal flow and how much flow input is required for the robust read-out of left-right determination remains unknown. Here we show that a local leftward flow generated by as few as two rotating cilia is sufficient to break left-right symmetry. Quantitative analysis of fluid flow and ciliary rotation in the node of mouse embryos shows that left-right asymmetry is already established within a few hours after the onset of rotation by a subset of nodal cilia. Examination of various ciliary mutant mice shows that two rotating cilia are sufficient to initiate left-right asymmetric gene expression. Our results suggest the existence of a highly sensitive system in the node that is able to sense an extremely weak unidirectional flow, and may favour a model in which the flow is sensed as a mechanical force.
authors.affiliation: Developmental Genetics Group, Graduate School of Frontier Biosciences, Osaka University, and Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan. shinohara@fbs.osaka-u.ac.jp
authors.forename: Kyosuke
authors.initials: K
authors.lastname: Shinohara
authors.forename: Aiko
authors.initials: A
authors.lastname: Kawasumi
authors.forename: Atsuko
authors.initials: A
authors.lastname: Takamatsu
authors.forename: Satoko
authors.initials: S
authors.lastname: Yoshiba
authors.forename: Yanick
authors.initials: Y
authors.lastname: Botilde
authors.forename: Noboru
authors.initials: N
authors.lastname: Motoyama
authors.forename: Walter
authors.initials: W
authors.lastname: Reith
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Durand
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Shiratori
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hamada
mesh_terms: D000818:Animals; D001703:Biophysics / Q000379:methods; D019521:Body Patterning / Q000235:genetics*; D002923:Cilia / Q000502:physiology*; D015509:Developmental Biology / Q000379:methods; D046149:Embryo Culture Techniques; D004622:Embryo, Mammalian / Q000378:metabolism* / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D008747:Methylcellulose / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D008954:Models, Biological; D009154:Mutation; D020897:Organizers, Embryonic / Q000502:physiology; D013997:Time Factors
chemical_list: D008747:Methylcellulose