|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Development, Vol 127, Issue 13 2853-2862, Copyright © 2000 by Company of Biologists
JOURNAL ARTICLES |
GJ Kim, A Yamada and H Nishida
Department of Life Science, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
The major mesodermal tissues of ascidian larvae are muscle, notochord and mesenchyme. They are derived from the marginal zone surrounding the endoderm area in the vegetal hemisphere. Muscle fate is specified by localized ooplasmic determinants, whereas specification of notochord and mesenchyme requires inducing signals from endoderm at the 32-cell stage. In the present study, we demonstrated that all endoderm precursors were able to induce formation of notochord and mesenchyme cells in presumptive notochord and mesenchyme blastomeres, respectively, indicating that the type of tissue induced depends on differences in the responsiveness of the signal-receiving blastomeres. Basic fibroblast growth factor (bFGF), but not activin A, induced formation of mesenchyme cells as well as notochord cells. Treatment of mesenchyme-muscle precursors isolated from early 32-cell embryos with bFGF promoted mesenchyme fate and suppressed muscle fate, which is a default fate assigned by the posterior-vegetal cytoplasm (PVC) of the eggs. The sensitivity of the mesenchyme precursors to bFGF reached a maximum at the 32-cell stage, and the time required for effective induction of mesenchyme cells was only 10 minutes, features similar to those of notochord induction. These results support the idea that the distinct tissue types, notochord and mesenchyme, are induced by the same signaling molecule originating from endoderm precursors. We also demonstrated that the PVC causes the difference in the responsiveness of notochord and mesenchyme precursor blastomeres. Removal of the PVC resulted in loss of mesenchyme and in ectopic notochord formation. In contrast, transplantation of the PVC led to ectopic formation of mesenchyme cells and loss of notochord. Thus, in normal development, notochord is induced by an FGF-like signal in the anterior margin of the vegetal hemisphere, where PVC is absent, and mesenchyme is induced by an FGF-like signal in the posterior margin, where PVC is present. The whole picture of mesodermal patterning in ascidian embryos is now known. We also discuss the importance of FGF induced asymmetric divisions, of notochord and mesenchyme precursor blastomeres at the 64-cell stage.
This article has been cited by other articles:
|
|
 |
|
  W. Shi and M. Levine Ephrin signaling establishes asymmetric cell fates in an endomesoderm lineage of the Ciona embryo Development, March 1, 2008; 135(5): 931 - 940. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. J. Kim, G. Kumano, and H. Nishida 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, April 15, 2007; 134(8): 1509 - 1518. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Hudson and H. Yasuo A signalling relay involving Nodal and Delta ligands acts during secondary notochord induction in Ciona embryos Development, August 1, 2006; 133(15): 2855 - 2864. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Kobayashi, K. Sawada, H. Yamamoto, S. Wada, H. Saiga, and H. Nishida 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, November 1, 2003; 130(21): 5179 - 5190. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Davidson and M. Levine Evolutionary origins of the vertebrate heart: Specification of the cardiac lineage in Ciona intestinalis PNAS, September 30, 2003; 100(20): 11469 - 11473. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. S. Imai, N. Satoh, and Y. Satou A Twist-like bHLH gene is a downstream factor of an endogenous FGF and determines mesenchymal fate in the ascidian embryos Development, September 15, 2003; 130(18): 4461 - 4472. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Kondoh, K. Kobayashi, and H. Nishida Suppression of macho-1-directed muscle fate by FGF and BMP is required for formation of posterior endoderm in ascidian embryos Development, July 15, 2003; 130(14): 3205 - 3216. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Wada and H. Saiga HrzicN, a new Zic family gene of ascidians, plays essential roles in the neural tube and notochord development Development, March 14, 2003; 129(24): 5597 - 5608. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Hudson, S. Darras, D. Caillol, H. Yasuo, and P. Lemaire A conserved role for the MEK signalling pathway in neural tissue specification and posteriorisation in the invertebrate chordate, the ascidian Ciona intestinalis Development, January 1, 2003; 130(1): 147 - 159. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. S. Imai, N. Satoh, and Y. Satou Early embryonic expression of FGF4/6/9 gene and its role in the induction of mesenchyme and notochord in Ciona savignyi embryos Development, January 4, 2002; 129(7): 1729 - 1738. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Satou, K. S. Imai, and N. Satoh 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, September 15, 2001; 128(18): 3559 - 3570. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Darras and H. Nishida The BMP signaling pathway is required together with the FGF pathway for notochord induction in the ascidian embryo Development, July 15, 2001; 128(14): 2629 - 2638. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Shimauchi, S. D. Murakami, and N. Satoh FGF signals are involved in the differentiation of notochord cells and mesenchyme cells of the ascidian Halocynthia roretzi Development, July 15, 2001; 128(14): 2711 - 2721. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Minokawa, K. Yagi, K. W. Makabe, and H. Nishida Binary specification of nerve cord and notochord cell fates in ascidian embryos Development, June 1, 2001; 128(11): 2007 - 2017. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Tanaka-Kunishima and K. Takahashi Cleavage-arrested cell triplets from ascidian embryo differentiate into three cell types depending on cell combination and contact timing J. Physiol., April 1, 2002; 540(1): 153 - 176. [Abstract] [Full Text] [PDF]
|
|
