Early Embryonic Axis Formation in a Simple Chordate Ascidian

  • Gaku KumanoEmail author
Part of the Diversity and Commonality in Animals book series (DCA)


Embryonic axes are established during early embryogenesis in animal development and serve as frameworks upon which embryonic body structures are built. A variety of tissue precursors are arranged along embryonic axes. Therefore, elucidation of the mechanisms by which these axes form in early embryos is fundamental in understanding how animal development proceeds, and this has become one of the most important questions in the field of developmental biology. In this chapter, axis formation mechanisms in the eggs and early embryos of marine invertebrates and simple chordates—ascidians—are presented. This information provides an opportunity to better understand the comprehensive and unique axis formation story of this particular animal species. However, generally important concepts of embryonic axis formation are interspersed throughout the axis-forming processes in ascidians. Therefore, readers should appreciate the complex and fascinating strategy underlying the establishment of early embryonic axes for the later development of ascidians and find the comparison of these mechanisms with those utilized in other organisms interesting.


Animal-vegetal Ascidian Ascidian Maternal determinant Dorsal-ventral Embryonic axis formation Left–right asymmetry Ooplasmic movements Postplasmic/PEM RNA 



I would like to thank the members of the Nishida Lab at Osaka University and the researchers at the Asamushi Research Center for Marine Biology at Tohoku University for stimulating discussions.


  1. Bakkers J, Verhoeven MC, Abdeliah-Seyfried S (2009) Shaping the zebrafish heat: from left–right axis specification to epithelial tissue morphogenesis. Dev Biol 330:213–220CrossRefPubMedGoogle Scholar
  2. Bates WR, Jeffery WR (1987) Localization of axial determinants in the vegetal pole region of ascidian eggs. Dev Biol 124:65–76CrossRefGoogle Scholar
  3. Becalska AN, Gavis ER (2009) Lighting up mRNA localization in Drosophila oogenesis. Development 136:2493–2503CrossRefPubMedPubMedCentralGoogle Scholar
  4. Blum M, Feistel K, Thumberger T, Schweickert A (2014a) The evolution and conservation of left–right patterning mechanisms. Development 141:1603–1613CrossRefPubMedGoogle Scholar
  5. Blum M, Schweickert A, Vick P, Wright CV, Danilchik MV (2014b) Symmetry breakage in the vertebrate embryo: when does it happen and how does it work? Dev Biol 393:109–123CrossRefPubMedPubMedCentralGoogle Scholar
  6. Chiba S, Miki Y, Ashida K, Wada MR, Tanaka KJ, Shibata Y, Nakamori R, Nishikata T (1999) Interactions between cytoskeletal components during myoplasm rearrangement in ascidian eggs. Develop Growth Differ 41:265–272CrossRefGoogle Scholar
  7. Conklin EG (1905) The organization and cell lineage of the ascidian egg. J Acad Natl Sci Phila 13:1–119Google Scholar
  8. Deng M, Suraneni P, Schultz RM, Li R (2007) The Ran GTPase mediates chromatin signaling to control cortical polarity during polar body extrusion in mouse oocytes. Dev Cell 12:301–308CrossRefPubMedGoogle Scholar
  9. Fujinaga M (1997) Development of sidedness of asymmetric body structures in vertebrates. Int J Dev Biol 41:153–186PubMedGoogle Scholar
  10. Gavis ER, Lehmann R (1992) Localization of nanos RNA controls embryonic polarity. Cell 71:301–313CrossRefPubMedGoogle Scholar
  11. Goldstein B, Hird SN (1996) Specification of the anteroposterior axis in Caenorhabditis elegans. Development 122:1467–1474PubMedGoogle Scholar
  12. Goldstein B, Frisse LM, Thomas WK (1998) Embryonic axis specification in nematodes: evolution of the first step in development. Curr Biol 8:157–160CrossRefPubMedGoogle Scholar
  13. Grande C, Patel NH (2009) Lophotrochozoa get into the game: the nodal pathway and left/right asymmetry in Bilateria. Cold Spring Harb Symp Quant Biol 74:281–287CrossRefPubMedGoogle Scholar
  14. Hamada H, Tam PP (2014) Mechanisms of left–right asymmetry and patterning: driver, mediator and responder. F100Prime Rep 6:110Google Scholar
  15. Hashimoto H, Enomoto T, Kumano G, Nishida H (2011) The transcription factor FoxB mediates temporal loss of cellular competence for notochord induction in ascidian embryos. Development 138:2591–2600CrossRefPubMedGoogle Scholar
  16. Hibino T, Nishikata T, Nishida H (1998) Centrosome-attracting body: a novel structure closely related to unequal cleavages in the ascidian embryo. Develop Growth Differ 40:85–95CrossRefGoogle Scholar
  17. Hird SN, White JG (1993) Cortical and cytoplasmic flow polarity in early embryonic cells of Caenorhabditis elegans. J Cell Biol 121:1343–1355CrossRefPubMedGoogle Scholar
  18. Houston DW (2013) Regulation of cell polarity and RNA localization in vertebrate oocytes. Int Rev Cell Mol Biol 306:127–185CrossRefPubMedGoogle Scholar
  19. Hudson C, Kawai N, Negishi T, Yasuo H (2013) β-Catenin-driven binary fate specification segregates germ layers in ascidian embryos. Curr Biol 23:491–495CrossRefPubMedGoogle Scholar
  20. Imai K, Takada N, Satoh N, Satou Y (2000) Beta-catenin mediates the specification of endoderm cells in ascidian embryos. Development 127:3009–3020PubMedGoogle Scholar
  21. Imai KS, Satoh N, Satou Y (2002a) Early embryonic expression of FGF4/6/9 gene and its role in the induction of mesenchyme and notochord in Ciona savignyi embryos. Development 129:1729–1738PubMedGoogle Scholar
  22. Imai KS, Satoh N, Satou Y (2002b) An essential role of a FoxD gene in notochord induction in Ciona embryos. Development 129:3441–3453PubMedGoogle Scholar
  23. Imai KS, Satoh N, Satou Y (2003) A twist-like bHLH gene is a downstream factor of an endogenous FGF and determines mesenchymal fate in the ascidian embryos. Development 130:4461–4472CrossRefPubMedGoogle Scholar
  24. Kawai N, Iida Y, Kumano G, Nishida H (2007) Nuclear accumulation of beta-catenin and transcription of downstream genes are regulated by zygotic Wnt5alpha and maternal Dsh in ascidian embryos. Dev Dyn 236:1570–1582CrossRefPubMedGoogle Scholar
  25. Kawakami R, Dobi A, Shigemori R, Ito I (2008) Right isomerism of the brain in inversus viscerum mutant mice. PLoS One 3:e1945CrossRefPubMedPubMedCentralGoogle Scholar
  26. Kim GJ, Nishida H (1999) Suppression of muscle fate by cellular interaction is required for mesenchyme formation during ascidian embryogenesis. Dev Biol 214:9–22CrossRefPubMedGoogle Scholar
  27. Kim GJ, Yamada A, Nishida H (2000) An FGF signal from endoderm and localized factors in the posterior-vegetal egg cytoplasm pattern the mesodermal tissues in the ascidian embryo. Development 127:2853–2862PubMedGoogle Scholar
  28. Kim GJ, Kumano G, Nishida H (2007) Cell fate polarization in ascidian mesenchyme/muscle precursors by directed FGF signaling and role for an additional ectodermal FGF antagonizing signal in notochord/nerve cord precursors. Development 134:1509–1518CrossRefPubMedGoogle Scholar
  29. Kloc M, Bilinski S, Chan AP, Allen LH, Zearfoss NR, Etkin LD (2001) RNA localization and germ cell determination in Xenopus. Int Rev Cytol 203:63–91CrossRefPubMedGoogle Scholar
  30. Kobayashi K, Sawada K, Yamamoto H, Wada S, Saiga H, Nishida H (2003) Maternal macho-1 is an intrinsic factor that makes cell response to the same FGF signal differ between mesenchyme and notochord induction in ascidian embryos. Development 130:5179–5190CrossRefPubMedGoogle Scholar
  31. Kondoh K, Kobayashi K, Nishida H (2003) Suppression of macho-1-directed muscle fate by FGF and BMP is required for formation of posterior endoderm in ascidian embryos. Development 130:3205–3216CrossRefPubMedGoogle Scholar
  32. Kumano G (2012) Polarizing animal cells via mRNA localization in oogenesis and early development. Develop Growth Differ 54:1–18CrossRefGoogle Scholar
  33. Kumano G, Nishida H (2007) Ascidian embryonic development: an emerging model system for the study of cell fate specification in chordates. Dev Dyn 236:1732–1747CrossRefPubMedGoogle Scholar
  34. Kumano G, Nishida H (2009) Patterning of an ascidian embryo along the anterior–posterior axis through spatial regulation of competence and induction ability by maternally localized PEM. Dev Biol 331:78–88CrossRefPubMedGoogle Scholar
  35. Kumano G, Smith WC (2002) Revisions to the Xenopus gastrula fate map: implications for mesoderm induction and patterning. Dev Dyn 225:409–421CrossRefPubMedGoogle Scholar
  36. Kumano G, Yamaguchi S, Nishida H (2006) Overlapping expression of FoxA and Zic confers responsiveness to FGF signaling to specify notochord in ascidian embryos. Dev Biol 300:770–784CrossRefPubMedGoogle Scholar
  37. Kumano G, Takatori N, Negishi T, Takada T, Nishida H (2011) A maternal factor unique to ascidians silences the germline via binding to P-TEFb and RNAP II regulation. Curr Biol 21:1308–1313CrossRefPubMedGoogle Scholar
  38. Kumano G, Negoro N, Nishida H (2014) Transcription factor Tbx6 plays a central role in fate determination between mesenchyme and muscle in embryos of the ascidian, Halocynthia roretzi. Develop Growth Differ 56:310–322CrossRefGoogle Scholar
  39. Lamy C, Rothbächer U, Caillol D, Lemaire P (2006) Ci-FoxA-a is the earliest zygotic determinant of the ascidian anterior ectoderm and directly activates Ci-sFRP1/5. Development 133:2835–2844CrossRefPubMedGoogle Scholar
  40. Lane MC, Sheets MD (2002) Primitive and definitive blood share a common origin in Xenopus: a comparison of lineage techniques used to construct fate maps. Dev Biol 248:52–67CrossRefPubMedGoogle Scholar
  41. Lane MC, Smith WC (1999) The origins of primitive blood in Xenopus: implications for axial patterning. Development 126:423–434PubMedGoogle Scholar
  42. Langdon YG, Mullins MC (2011) Maternal and zygotic control of zebrafish dorsoventral axial patterning. Annu Rev Genet 45:357–377CrossRefPubMedGoogle Scholar
  43. Lemaire P (2009) Unfolding a chordate developmental program, one cell at a time: invariant cell lineages, short-range inductions and evolutionary plasticity in ascidians. Dev Biol 332:48–60CrossRefPubMedGoogle Scholar
  44. Lemaire P, Smith WC, Nishida H (2008) Ascidians and the plasticity of the chordate developmental program. Curr Biol 18:R620–R631CrossRefPubMedPubMedCentralGoogle Scholar
  45. Li R, Albertini DF (2013) The road to maturation: somatic cell interaction and self-organization of the mammalian oocyte. Nat Rev Mol Cell Biol 14:141–152CrossRefPubMedGoogle Scholar
  46. Makabe KW, Nishida H (2012) Cytoplasmic localization and reorganization in ascidian eggs: role of postplasmic/PEM RNAs in axis formation and fate determination. Wiley Interdiscip Rev Dev Biol 1:501–518CrossRefPubMedGoogle Scholar
  47. Minokawa T, Yagi K, Makabe KW, Nishida H (2001) Binary specification of nerve cord and notochord cell fates in ascidian embryos. Development 128:2007–2017PubMedGoogle Scholar
  48. Morokuma J, Ueno M, Kawanishi H, Saiga H, Nishida H (2002) HrNodal, the ascidian nodal-related gene, is expressed in the left side of the epidermis, and lies upstream of HrPitx. Dev Genes Evol 212:439–446CrossRefPubMedGoogle Scholar
  49. Motegi F, Zonies S, Hao Y, Cuenca AA, Griffin E, Seydoux G (2011) Microtubules induce self-organization of polarized PAR domains in Caenorhabditis elegans zygotes. Nat Cell Biol 13:1361–1367CrossRefPubMedPubMedCentralGoogle Scholar
  50. Mukai H, Watanabe H (1976) Studies on the formation of germ cells in a compound ascidian Botryllus primigenus. Oka. J Morphol 148:362–377CrossRefGoogle Scholar
  51. Munro E, Nance J, Priess JR (2004) Cortical flows powered by asymmetrical contraction transport PAR proteins to establish and maintain anterior–posterior polarity in the early C. elegans embryo. Dev Cell 7:413–424CrossRefPubMedGoogle Scholar
  52. Nakamura Y, Makabe KW, Nishida H (2005) POPK-1/Sad-1 kinase is required for the proper translocation of maternal mRNAs and putative germ plasm at the posterior pole of the ascidian embryo. Development 132:4731–4742CrossRefPubMedGoogle Scholar
  53. Nakatani Y, Yasuo H, Satoh N, Nishida H (1996) Basic fibroblast growth factor induces notochord formation and the expression of As-T, a Brachyury homolog, during ascidian embryogenesis. Development 122:2023–2031PubMedGoogle Scholar
  54. Namigai EK, Kenny NJ, Shimeld SM (2014) Right across the tree of life: the evolution of left–right asymmetry in the Bilateria. Genesis 52:458–470CrossRefPubMedGoogle Scholar
  55. Negishi T, Takada T, Kawai N, Nishida H (2007) Localized PEM mRNA and protein are involved in cleavage-plane orientation and unequal cell divisions in ascidians. Curr Biol 17:1014–1025CrossRefPubMedGoogle Scholar
  56. Nishida H (1987) Cell lineage analysis in ascidian embryos by intracellular injection of a tracer enzyme. III Up to the tissue restricted stage. Dev Biol 121:526–541CrossRefPubMedGoogle Scholar
  57. Nishida H (1993) Localized regions of egg cytoplasm that promote expression of endoderm-specific alkaline phosphatase in embryos of the ascidian Halocynthia roretzi. Development 118:1–7Google Scholar
  58. Nishida H (1994) Localization of determinants for formation of the anterior–posterior axis in eggs of the ascidian Halocynthia roretzi. Development 120:3093–3104Google Scholar
  59. Nishida H (1996) Vegetal egg cytoplasm promotes gastrulation and is responsible for specification of vegetal blastomeres in embryos of the ascidian Halocynthia roretzi. Development 122:1271–1279PubMedGoogle Scholar
  60. Nishida H (2003) Spatio-temporal pattern of MAP kinase activation in embryos of the ascidian Halocynthia roretzi. Develop Growth Differ 45:27–37CrossRefGoogle Scholar
  61. Nishida H (2005) Specification of embryonic axis and mosaic development in ascidians. Dev Dyn 233:1177–1193CrossRefPubMedGoogle Scholar
  62. Nishida H, Sawada K (2001) Macho-1 encodes a localized mRNA in ascidian eggs that specifies muscle fate during embryogenesis. Nature 409:724–729CrossRefPubMedGoogle Scholar
  63. Nishida H, Stach T (2014) Cell lineages and fate maps in tunicates: conservation and modification. Zool Sci 31:645–652CrossRefPubMedGoogle Scholar
  64. Nishide K, Mugitani M, Kumano G, Nishida H (2012) Neurula rotation determines left–right asymmetry in ascidian tadpole larvae. Development 139:1467–1475CrossRefPubMedGoogle Scholar
  65. Olson DJ, Oh D, Houston DW (2015) The dynamics of plus end polarization and microtubule assembly during Xenopus cortical rotation. Dev Biol 401:249–263CrossRefPubMedPubMedCentralGoogle Scholar
  66. Paix A, Le Nguyen PN, Sardet C (2011) Bi-polarized translation of ascidian maternal mRNA determinant pem-1 associated with regulators of the translation machinery on cortical endoplasmic reticulum (cER). Dev Biol 357:211–226CrossRefPubMedGoogle Scholar
  67. Picco V, Hudson C, Yasuo H (2007) Ephrin-Eph signaling drives the asymmetric division of notochord/neural precursors in Ciona embryos. Development 134:1491–1497CrossRefPubMedGoogle Scholar
  68. Prodon F, Dru P, Roegiers F, Sardet C (2005) Polarity of the ascidian egg cortex and relocalization of cER and mRNAs in the early embryo. J Cell Sci 118:2393–2404CrossRefPubMedGoogle Scholar
  69. Prodon F, Chenevert J, Sardet C (2006) Establishment of animal–vegetal polarity during maturation in ascidian oocytes. Dev Biol 290:297–311CrossRefPubMedGoogle Scholar
  70. Prodon F, Yamada L, Shirae-Kurabayashi M, Nakamura Y, Sasakura Y (2007) Postplasmic/PEM RNAs: a class of localized maternal mRNAs with multiple roles in cell polarity and development in ascidian embryos. Dev Dyn 236:1698–1715CrossRefPubMedGoogle Scholar
  71. Prodon F, Sardet C, Nishida H (2008) Cortical and cytoplasmic flows driven by actin microfilaments polarize the cortical ER-mRNA domain along the a–v axis in ascidian oocytes. Dev Biol 313:682–699CrossRefPubMedGoogle Scholar
  72. Prodon F, Chenevert J, Hébras C, Dumollard R, Faure E, Gonzalez-Garcia J, Nishida H, Sardet C, McDougall A (2010) Dural mechanism controls asymmetric spindle position in ascidian germ cell precursors. Development 137:2011–2021CrossRefPubMedGoogle Scholar
  73. Riechmann V, Ephrussi A (2001) Axis formation during Drosophila oogenesis. Curr Opin Genet Dev 11:374–383CrossRefPubMedGoogle Scholar
  74. Roegiers F, McDougall A, Sardet C (1995) The sperm entry point defines the orientation of the calcium-induced contraction wave that directs the first phase of cytoplasmic reorganization in the ascidian egg. Development 121:3457–3466PubMedGoogle Scholar
  75. Roegiers F, Djediat C, Dumollard R, Rouviere C, Sardet C (1999) Phases of cytoplasmic and cortical reorganizations of the ascidian zygote between fertilization and first division. Development 126:3101–3117PubMedGoogle Scholar
  76. Rothbächer U, Bertrand V, Lamy C, Lemaire P (2007) A combinatorial code of maternal GATA, Ets and beta-catenin-TCF transcription factors specifies and patterns the early ascidian ectoderm. Development 134:4023–4032CrossRefPubMedGoogle Scholar
  77. Rowning BA, Wells J, Wu M, Gerhart JC, Moon RT, Larabell CA (1997) Microtubule-mediated transport of organelles and localization of beta-catenin to the future dorsal side of Xenopus eggs. Proc Natl Acad Sci U S A 94:1224–1229CrossRefPubMedPubMedCentralGoogle Scholar
  78. Sakari K, Shirai H (1991) Possible MIS production by follicle cells in spontaneous oocyte maturation of the ascidian Halocynthia roretzi. Develop Growth Differ 33:155–162CrossRefGoogle Scholar
  79. Sardet C, Speksnijder JE, Terasaki M, Chang P (1992) Polarity of the ascidian egg cortex before fertilization. Development 115:221–237PubMedGoogle Scholar
  80. Sardet C, Nishida H, Prodon F, Sawada K (2003) Maternal mRNAs of PEM and macho-1, the ascidian muscle determinant, associate and move with a rough endoplasmic reticulum network in the egg cortex. Development 130:5839–5849CrossRefPubMedGoogle Scholar
  81. Sardet C, Paix A, Prodon F, Dru P, Chenevert J (2007) From oocyte to 16-cell stage: cytoplasmic and cortical reorganizations that pattern the ascidian embryo. Dev Dyn 236:1716–1731CrossRefPubMedGoogle Scholar
  82. Sasakura Y, Ogasawara M, Makabe KW (1998) Maternally localized RNA encoding a serine/threonine protein kinase in the ascidian Halocynthia roretzi. Mech Dev 76:161–163CrossRefPubMedGoogle Scholar
  83. Satoh N, Rokhsar D, Nishikawa T (2014) Chordate evolution and the three-phylum system. Proc Biol Sci 281:20141729CrossRefPubMedPubMedCentralGoogle Scholar
  84. Satou Y, Imai KS, Satoh N (2001) Early embryonic expression of a LIM-homeobox gene CS-lhx3 is downstream of beta-catenin and responsible for the endoderm differentiation in Ciona savignyi embryos. Development 128:3559–3570PubMedGoogle Scholar
  85. Satou Y, Yagi K, Imai KS, Yamada L, Nishida H, Satoh N (2002) Macho-1 related genes in Ciona embryos. Dev Genes Evol 212:87–92CrossRefPubMedGoogle Scholar
  86. Sawada T, Schatten G (1988) Microtubules in ascidian eggs during meiosis, fertilization, and mitosis. Cell Motil Cytoskeleton 9:219–230CrossRefPubMedGoogle Scholar
  87. Schlueter J, Brand T (2007) Left–right axis development: examples of similar and divergent strategies to generate asymmetric morphogenesis in chick and mouse embryos. Cytogenet Genome Res 117:256–267CrossRefPubMedGoogle Scholar
  88. Shi W, Levine M (2008) Ephrin signaling establishes asymmetric cell fates in an endomesoderm lineage of the Ciona embryo. Development 135:931–940CrossRefPubMedGoogle Scholar
  89. Shirae-Kurabayashi M, Matsuda K, Nakamura A (2011) Ci-Pem-1 localizes to the nucleus and represses somatic gene transcription in the germline of Ciona intestinalis embryos. Development 138:2871–2881CrossRefPubMedGoogle Scholar
  90. Takatori N, Kumano G, Saiga H, Nishida H (2010) Segregation of germ layer fates by nuclear migration-dependent localization of Not mRNA. Dev Cell 19:589–598CrossRefPubMedGoogle Scholar
  91. Taniguchi K, Nishida H (2004) Tracing cell fate in brain formation during embryogenesis of the ascidian Halocynthia roretzi. Develop Growth Differ 46:163–180CrossRefGoogle Scholar
  92. Tanaka KJ, Matsumoto K, Tsujimoto M, Nishikata T (2004) CiYB1 is a major component of storage mRNPs in ascidian oocytes: implications in translational regulation of localized mRNAs. Dev Biol 272:217–230CrossRefPubMedGoogle Scholar
  93. Tokuhisa M, Muto M, Nishida H (2017) Eccentric position of the germinal vesicle and cortical flow during oocyte maturation specify the animal-vegetal axis of ascidian embryos. Development 144:897–904CrossRefPubMedGoogle Scholar
  94. Takatori N, Oonuma K, Nishida H, Saiga H (2015) Polarization of PI3K activity initiated by ooplasmic segregation guides nuclear migration in the mesendoderm. Dev Cell 35:333–343CrossRefPubMedGoogle Scholar
  95. Tran LD, Hino H, Quach H, Lim S, Shindo A, Mimori-Kiyosue Y, Mione M, Ueno N, Winkler C, Hibi M, Sampath K (2012) Dynamic microtubules at the vegetal cortex predict the embryonic axis in zebrafish. Development 139:3644–3652CrossRefPubMedGoogle Scholar
  96. White JA, Heasman J (2008) Maternal control of pattern formation in Xenopus laevis. J Exp Zool B Mol Dev Evol 310:73–84CrossRefPubMedGoogle Scholar
  97. Yi K, Rubinstein B, Li R (2013) Symmetry breaking and polarity establishment during mouse oocyte maturation. Philos Trans R Soc Lond Ser B Biol Sci 368:20130002CrossRefGoogle Scholar
  98. Yoshida K, Saiga H (2011) Repression of Rx gene on the left side of the sensory vesicle by nodal signaling is crucial for right-sided formation of the ocellus photoreceptor in the development of Ciona intestinalis. Dev Biol 354:144–150CrossRefPubMedGoogle Scholar
  99. Yoshida K, Siaga H (2008) Left–right asymmetric expression of Pitx is regulated by the asymmetric nodal signaling through an intronic enhancer in Ciona intestinalis. Dev Genes Evol 218:353–360CrossRefPubMedGoogle Scholar
  100. Yoshida S, Marikawa Y, Satoh N (1996) Posterior end mark, a novel maternal gene encoding a localized factor in the ascidian embryo. Development 122:2005–2012PubMedGoogle Scholar

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© Springer Japan KK, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Asamushi Research Center for Marine Biology, Graduate School of Life ScienceTohoku UniversityAomoriJapan

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