Chiral forces organize left-right patterning in C. elegans by uncoupling midline and anteroposterior axis.

Left-right (LR) patterning is an intriguing but poorly understood process of bilaterian embryogenesis. We report a mechanism for LR patterning in C. elegans in which the embryo uncouples its midline from the anteroposterior (AP) axis. Specifically, the eight-cell embryo establishes a midline that is tilted rightward from the AP axis and positions more cells on the left, allowing subsequent differential LR fate inductions. To establish the tilted midline, cells exhibit LR asymmetric protrusions and a handed collective movement. This process, termed chiral morphogenesis, involves differential regulation of cortical contractility between a pair of sister cells that are bilateral counterparts fate-wise and is activated by noncanonical Wnt signaling. Chiral morphogenesis is timed by the cytokinetic furrow of a neighbor of the sister pair, providing a developmental clock and an unexpected signaling interaction between the contractile ring and the adjacent cells.

[1]  C. Mello,et al.  SRC-1 and Wnt signaling act together to specify endoderm and to control cleavage orientation in early C. elegans embryos. , 2002, Developmental cell.

[2]  R. Waterston,et al.  Automated cell lineage tracing in Caenorhabditis elegans. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[3]  L. Wolpert,et al.  The development of handedness in left/right asymmetry. , 1990, Development.

[4]  K. Oegema,et al.  Anillin and the septins promote asymmetric ingression of the cytokinetic furrow. , 2007, Developmental cell.

[5]  D. Baillie,et al.  A Formin Homology Protein and a Profilin Are Required for Cytokinesis and Arp2/3-Independent Assembly of Cortical Microfilaments in C. elegans , 2002, Current Biology.

[6]  J. Priess,et al.  Left-right asymmetry in C. elegans intestine organogenesis involves a LIN-12/Notch signaling pathway. , 2000, Development.

[7]  M. Mlodzik,et al.  Frizzled/PCP signalling: a conserved mechanism regulating cell polarity and directed motility , 2007, Nature Reviews Genetics.

[8]  John Isaac Murray,et al.  The lineaging of fluorescently-labeled Caenorhabditis elegans embryos with StarryNite and AceTree , 2006, Nature Protocols.

[9]  C. Tabin,et al.  Cell Movements at Hensen’s Node Establish Left/Right Asymmetric Gene Expression in the Chick , 2009, Science.

[10]  T. Holak,et al.  Lifeact: a versatile marker to visualize F-actin , 2008, Nature Methods.

[11]  R. Kuroda,et al.  Chiral blastomere arrangement dictates zygotic left–right asymmetry pathway in snails , 2009, Nature.

[12]  Bob Goldstein,et al.  Wnt/Frizzled Signaling Controls C. elegans Gastrulation by Activating Actomyosin Contractility , 2006, Current Biology.

[13]  W. Wood.  Evidence from reversal of handedness in C. elegans embryos for early cell interactions determining cell fates , 1991, Nature.

[14]  Rizwan U. Farooqui,et al.  Multiple rows of cells behind an epithelial wound edge extend cryptic lamellipodia to collectively drive cell-sheet movement , 2005, Journal of Cell Science.

[15]  K. Oegema,et al.  A complex containing the Sm protein CAR-1 and the RNA helicase CGH-1 is required for embryonic cytokinesis in Caenorhabditis elegans , 2005, The Journal of cell biology.

[16]  J. Priess,et al.  Cortical flows powered by asymmetrical contraction transport PAR proteins to establish and maintain anterior-posterior polarity in the early C. elegans embryo. , 2004, Developmental cell.

[17]  Kenneth M. Yamada,et al.  Defects in Cell Adhesion and the Visceral Endoderm following Ablation of Nonmuscle Myosin Heavy Chain II-A in Mice* , 2004, Journal of Biological Chemistry.

[18]  David E Hill,et al.  Toward improving Caenorhabditis elegans phenome mapping with an ORFeome-based RNAi library. , 2004, Genome research.

[19]  W. Wood,et al.  Maternal effect of low temperature on handedness determination in C. elegans embryos. , 1996, Developmental genetics.

[20]  H. Schnabel,et al.  Assessing normal embryogenesis in Caenorhabditis elegans using a 4D microscope: variability of development and regional specification. , 1997, Developmental biology.

[21]  S. Noselli,et al.  Strategies to establish left/right asymmetry in vertebrates and invertebrates. , 2007, Current opinion in genetics & development.

[22]  Bruce Bowerman,et al.  Wnt Signaling Polarizes an Early C. elegans Blastomere to Distinguish Endoderm from Mesoderm , 1997, Cell.

[23]  W. Wood,et al.  Multiple Wnt signaling pathways converge to orient the mitotic spindle in early C. elegans embryos. , 2004, Developmental cell.

[24]  T D Pollard,et al.  Molecular mechanisms controlling actin filament dynamics in nonmuscle cells. , 2000, Annual review of biophysics and biomolecular structure.

[25]  H. Hamada,et al.  The left-right axis in the mouse: from origin to morphology , 2006, Development.

[26]  R. Schnabel,et al.  A Posterior Centre Establishes and Maintains Polarity of the Caenorhabditis elegans Embryo by a Wnt-Dependent Relay Mechanism , 2006, PLoS biology.

[27]  Y. Dong,et al.  Systematic functional analysis of the Caenorhabditis elegans genome using RNAi , 2003, Nature.

[28]  C. Tabin.  Do we know anything about how left–right asymmetry is first established in the vertebrate embryo? , 2005, Journal of Molecular Histology.

[29]  B. Rongish,et al.  Rotation of Organizer Tissue Contributes to Left–Right Asymmetry , 2009, Anatomical record.

[30]  Lesilee S. Rose,et al.  Embryonic handedness choice in C. elegans involves the Gα protein GPA-16 , 2003 .

[31]  Zhirong Bao,et al.  AceTree: a tool for visual analysis of Caenorhabditis elegans embryogenesis , 2006, BMC Bioinformatics.

[32]  Lesilee S. Rose,et al.  LET-99 opposes Gα/GPR signaling to generate asymmetry for spindle positioning in response to PAR and MES-1/SRC-1 signaling , 2003, Development.

[33]  Zhirong Bao,et al.  Control of cell cycle timing during C. elegans embryogenesis. , 2008, Developmental biology.

[34]  S. Brenner.  The genetics of Caenorhabditis elegans. , 1974, Genetics.

[35]  Michael Levin,et al.  Left–right asymmetry in embryonic development: a comprehensive review , 2005, Mechanisms of Development.

[36]  R. Lin,et al.  POP-1 and Anterior–Posterior Fate Decisions in C. elegans Embryos , 1998, Cell.

[37]  W. Wood,et al.  Left-right asymmetry in animal development. , 1997, Annual review of cell and developmental biology.

[38]  James R Priess,et al.  Notch signaling in the C. elegans embryo. , 2005, WormBook : the online review of C. elegans biology.

[39]  R. Schnabel,et al.  Establishment of left-right asymmetry in the Caenorhabditis elegans embryo: a multistep process involving a series of inductive events. , 1995, Development.

[40]  N. Hirokawa,et al.  Nodal Flow and the Generation of Left-Right Asymmetry , 2006, Cell.

[41]  A. Wynshaw-Boris,et al.  Planar polarization of node cells determines the rotational axis of node cilia , 2010, Nature Cell Biology.

[42]  C. Mello,et al.  Wnt Signaling and an APC-Related Gene Specify Endoderm in Early C. elegans Embryos , 1997, Cell.

[43]  M. Meneghini,et al.  Wnt pathway components orient a mitotic spindle in the early Caenorhabditis elegans embryo without requiring gene transcription in the responding cell. , 1999, Genes & development.

[44]  J. Sulston,et al.  The embryonic cell lineage of the nematode Caenorhabditis elegans. , 1983, Developmental biology.

[45]  R. Lin,et al.  pop-1 Encodes an HMG box protein required for the specification of a mesoderm precursor in Early C. elegans embryos , 1995, Cell.

[46]  Zhirong Bao,et al.  Comparative analysis of embryonic cell lineage between Caenorhabditis briggsae and Caenorhabditis elegans. , 2008, Developmental biology.