|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Development, Vol 116, Issue 3 521-529, Copyright © 1992 by Company of Biologists
JOURNAL ARTICLES |
H. Nishida
Development of ascidians occurs in typical mosaic fashion: blastomeres isolated from early embryos differentiate into tissues according to their normal fates, an indication that cytoplasmic determinants exist in early blastomeres. To provide direct evidence for such cytoplasmic determinants, we have devised methods for fusing blastomeres and cytoplasmic fragments from various regions. (1) Presumptive-epidermis blastomeres were fused to cytoplasmic fragments from various regions of blastomeres of 8-cell embryos of Halocynthia roretzi and development of muscle cells was monitored by an antibody to ascidian myosin. Muscle differentiation was observed only when presumptive-epidermis blastomeres were fused with fragments from the posterior region of B4.1 (posterior-vegetal) blastomeres, the normal progenitor of muscle cells. The results indicate that muscle determinants are present and localized in the cytoplasm that enters muscle-lineage cells. (2) To investigate the presence and localization of muscle determinants in the egg, cytoplasmic fragments from various regions of unfertilized and fertilized eggs were fused with the presumptive- epidermis blastomeres, and formation of muscle cells was assessed by monitoring myosin, actin and acetylcholinesterase expression. These proteins were expressed only when cytoplasm from a restricted region of the eggs, i.e. the vegetal region, after the first phase of ooplasmic segregation, and posterior region, after the second phase of segregation, were fused. Based on these experiments, it is suggested that muscle determinants are segregated by ooplasmic movements after fertilization. They move initially to the vegetal pole of the egg and, prior to first cleavage, to the posterior region from whence future muscle-lineage blastomeres are formed. The inferred movements of muscle determinants correspond to those of the myoplasm, a microscopically visible portion of the egg cytoplasm.
This article has been cited by other articles:
|
|
 |
|
  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]
|
|
|
|
|
|
G. Kim, A Yamada, and H Nishida An FGF signal from endoderm and localized factors in the posterior-vegetal egg cytoplasm pattern the mesodermal tissues in the ascidian embryo Development, January 7, 2000; 127(13): 2853 - 2862. [Abstract] [PDF]
|
|
|
|
|
|
F Roegiers, C Djediat, R Dumollard, C Rouviere, and C Sardet Phases of cytoplasmic and cortical reorganizations of the ascidian zygote between fertilization and first division Development, January 6, 1999; 126(14): 3101 - 3117. [Abstract] [PDF]
|
|
|
|
|
|
T Miya, K Morita, A Suzuki, N Ueno, and N Satoh Functional analysis of an ascidian homologue of vertebrate Bmp-2/Bmp-4 suggests its role in the inhibition of neural fate specification Development, January 12, 1997; 124(24): 5149 - 5159. [Abstract] [PDF]
|
|
|
|
|
|
T. Meedel, S. Farmer, and J. Lee The single MyoD family gene of Ciona intestinalis encodes two differentially expressed proteins: implications for the evolution of chordate muscle gene regulation Development, January 5, 1997; 124(9): 1711 - 1721. [Abstract] [PDF]
|
|
|
|
|
|
J. Corbo, M Levine, and R. Zeller Characterization of a notochord-specific enhancer from the Brachyury promoter region of the ascidian, Ciona intestinalis Development, January 2, 1997; 124(3): 589 - 602. [Abstract] [PDF]
|
|
|
|
|
|
S Yoshida, Y Marikawa, and N Satoh Posterior end mark, a novel maternal gene encoding a localized factor in the ascidian embryo Development, January 7, 1996; 122(7): 2005 - 2012. [Abstract] [PDF]
|
|
|
|
|
|
Y Nakatani, H Yasuo, N Satoh, and H Nishida Basic fibroblast growth factor induces notochord formation and the expression of As-T, a Brachyury homolog, during ascidian embryogenesis Development, January 7, 1996; 122(7): 2023 - 2031. [Abstract] [PDF]
|
|
|
|
|
|
F Roegiers, A McDougall, and C Sardet 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, January 10, 1995; 121(10): 3457 - 3466. [Abstract] [PDF]
|
|
