Summary
Ooplasmic segregation in ascidians includes the movement of the myoplasm, a pigmented cytoplasmic region thought to be involved in the determination of the embryonic muscle and mesenchyme cell lineages, into the vegetal hemisphere of the egg. A myoplasmic cytoskeletal domain (MCD), composed of a cortical actin network (the PML) and an underlying filamentous lattice extending deep into the cytoplasm, is present in this region. The MCD gradually recedes into the vegetal hemisphere during ooplasmic segregation. It has been proposed that the segregation of the myoplasm is mediated by the contraction of the PML. To test this possibility we have examined ooplasmic segregation in eggs in which the internal parts of the MCD were separated from the PML by centrifugal force. Transmission and scanning electron microscopy of eggs extracted with Triton X-100 showed that the PML remained intact when the internal portions of the MCD were displaced and stratified by centrifugation. When stratified eggs were fertilized there were no rearrangements of the visible cytoplasmic inclusions, but the cellular deformations and the recession of the PML characteristic of ooplasmic segregation occurred as usual. The results indicate that the recession of the PML occurs independently of the internal constituents of the MCD and suggest that PML contraction is the motive force for ooplasmic segregation.
References
Bell WA, Holland ND (1974) Cholinesterase in larvae of the ascidian,Ciona intestinalis, developing from fragments cut from centrifuged eggs. Wilhelm Roux's Arch 175:91–102
Ben-Zéev A, Duerr A, Solomon F, Penman S (1979) The outer boundary of the cytoskeleton: A lamina derived from plasma membrane proteins. Cell 17:859–865
Conklin EG (1905) The organization and cell lineage of the ascidian egg. J Acad Natl Sci Phila 13:1–119
Conklin EG (1931) The development of centrifuged eggs of ascidians. J Exp Zool 60:1–119
Jeffery WR (1982) Calcium ionophore polarizes ooplasmic segregation in ascidian eggs. Science 216:545–547
Jeffery WR (1984) Pattern formation by ooplasmic segregation in ascidian eggs. Biol Bull [in press]
Jeffery WR, Meier S (1983) A yellow crescent cytoskeletal domain in ascidian eggs and its role in early development. Dev Biol 96:125–143
Jeffery WR, Tomlinson CR, Brodeur RD, Meier S (1984) The yellow crescent of ascidian eggs: Molecular organization, localization and role in early development. In: Malacinski GM and Klein WH (eds) Molecular aspects of early development. Plenum Press, New York, pp 1–38
La Spina R (1961) Development ofAscidia malaca egg fragments produced by centrifugation. Acta Embryol Morphol Exp 4:320–326
Mesland DAM, Los G, Spiele H (1981) Cytochalasin B disrupts the association of filamentous web and plasma membrane in hepatocytes. Exp Cell Res 135:431–435
Reverberi G (1937) Ricerche spermentali sulla struttura dell'uovo fecondo delle ascide. Com Pontif Acad Sci 1:135–172
Reverberi G (1975) Some effects of cytochalasin B on the eggs and tadpoles of ascidians. Acta Embryol Exp 2:137–158
Reverberi G, Ortolani G (1962) Twin larvae from halves of the same egg in ascidians. Dev Biol 5:84–100
Sawada T (1983) How ooplasm segregates bipolarly in ascidian eggs. Bull Mar Biol Stat Tohuku Univ 17:123–140
Sawada T, Osanai K (1981) The cortical contraction related to ooplasmic segregation inCiona intestinalis eggs. Wilhelm Roux's Arch 190:208–214
Sawada T, Osanai K (1984) Cortical contraction and ooplasmic movement in centrifuged or artificially constricted eggs ofCiona intestinalis. Wilhelm Roux's Arch 193:127–132
Sheetz M (1979) Intergral membrane protein interaction with Triton cytoskeletons of erythrocytes. Biochem Biophys Acta 557:122–134
Strauch AR, LaFountain JR (1982) Centrifugation shearing exposes filamentous networks in cortical regions of crane-fly spermatocytes. J Cell Biol 93:670–679
West AB, Lambert CC (1975) Control of spawning in the tunicateStyela plicata by variations in a natural light regime. J Exp Zool 195:265–270
Whittaker JR (1980) Acetylcholinesterase development in extra cells caused by changing the distribution of myoplasm in ascidian embryos. J Embryol Exp Morphol 55:343–354
Wilson EB (1925) The cell in development and heredity, 3rd ed., MacMillian, New York, pp 1035–1121
Zalokar M (1974) Effect of colchicine and cytochalasin B on ooplasmic segregation of ascidian eggs. Wilhelm Roux's Arch 175:243–248
Zalokar M (1979) Effect of cell-surface binding on development of ascidian egg. Wilhelm Roux's Archiv 187:243–248
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Jeffery, W.R., Meier, S. Ooplasmic segregation of the myoplasmic actin network in stratified ascidian eggs. Wilhelm Roux' Archiv 193, 257–262 (1984). https://doi.org/10.1007/BF01260348
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DOI: https://doi.org/10.1007/BF01260348