Two histospecific enzyme expressions in the same cleavage-arrested one-celled ascidian embryos (original) (raw)
Related papers
1990
Two muscle differentiation programs, acetylcholinesterase and tropomyosin-containing filaments and fibrils, occur together in the same cleavage-arrested zygotes (1-celled) of the ascidian Ciona intestinalis. Coexpression in such undivided but developing 'embryos' is consistent with the idea that separate elements of muscle differentiation are related at some regulatory level, perhaps through a single multi-gene regulatory factor. Fertilized Ciona eggs were exposed to cytochalasin B for 20 h and then briefly reacted histochemically for acetylcholinesterase activity. Strongly reacting specimens were selected and processed for transmission electron microscopy to reveal regions of muscle ultrastructure. Every acetylcholinesterase-reactive zygote tested contained muscle contractile elements; no example lacking acetylcholinesterase was found with myofilaments and myofibrils. As demonstrated by immunogold labelling, a polyclonal antibody to tropomyosin from Ciona adult body wall re...
Caryologia, 2006
The distribution of acetylcholinesterase (AChE) activity has been studied in ovary, unfertilized egg, embryos and larva of Ciona intestinalis and Ascidia malaca (Ascidiacea, Urochordata) by biochemical and histochemical methods. The biochemical results have shown that the AChE activity is detected in ovary, and in the egg before fertilization; it rises from 8-cell stage up to gastrula, neurula, and above all at swimming larva. Cholinesterase activity has been histochemically localized and the results of this study agree with the biochemical data. The distribution of the enzyme activity in ovary and in different stages of development suggests also a non-classical role on maturation of female gametes, on cell adhesiveness and interaction, on differentiation, on secretion and apoptosis process.
Developmental Biology, 1998
Alkaline phosphatase (AP) activity is expressed by endodermal cells of ascidian larvae. It was reported previously that the expression of AP activity is resistant to treatment with actinomycin D, a transcription inhibitor that inhibits the appearance of several other tissue-specific molecules and morphological markers of tissue formation in developing ascidians. The resistance of AP expression to actinomycin D treatment suggests that endodermal AP activity does not depend on zygotic transcription and that its appearance is mediated by the translational activation of maternal AP mRNA present in ascidian eggs. However, it was also shown that anucleate merogons do not develop AP activity. To directly examine whether maternal AP transcripts are present in the cytoplasm of eggs, we isolated a cDNA of an endoderm-specific AP in Halocyuthia roretzi and examined the temporal and spatial expressions of this gene during embryogenesis using Northern blots and in situ hybridization. Maternal AP transcripts were detected in oocytes, cleaving-stage embryos, and in gastrnlae, and endoderm-specific AP transcripts dramatically increased about 14 times from the neurnla stage to the larval stage in endoderm precursor cells. These results suggest that the differentiation of endoderm is primarily correlated with the activation of zygotic transcription of the AP gene, presumably by egg cytoplasmic factors, similar to how muscle and epidermis are believed to develop.
Development, 1991
The myoplasm of ascidian eggs is a localized cytoskeletal domain that is segregated to presumptive larval tail muscle cells during embryonic development. We have identified a cytoskeletal protein recognized by a vertebrate neurofilament monoclonal antibody (NN18) which is concentrated in the myoplasm in eggs and embryos of a variety of ascidian species. The NN18 antigen is localized in the periphery of unfertilized eggs, segregates with the myoplasm after fertilization, and enters the larval tail muscle cells during embryonic development. Western blots of one-dimensional and twodimensional gels showed that the major component recognized by NN18 antibody is a SSxKh'Af,. protein (p58), which exists in at least three different isoforms. The enrichment of p58 in the Triton X-100-insoluble fraction of eggs and its reticular staining pattern in eggs and embryos suggests that it is a cytoskeletal protein. In subsequent experiments, p58 was used as a marker to determine whether changes in the myoplasm occur in eggs of anural ascidian species, i.e. those exhibiting a life cycle lacking tadpole larvae with differentiated muscle cells. Although p58 was localized in the myoplasm in eggs of four urodele ascidian species that develop into swimming tadpole larvae, this protein was distributed uniformly in eggs of three anural ascidian species. The eggs of two of these anural species contained the actin lamina, another component of the myoplasm, whereas the third anural species lacked the actin lamina. There was no detectible localization of p58 after fertilization or segregation into muscle lineage cells during cleavage of anural eggs. NN18 antigen was uniformly distributed in pre-vitellogenic oocytes and then localized in the perinuclear zone during vitellogenesis of urodele and anural ascidians. Subsequently, NN18 antigen was concentrated in the peripheral cytoplasm of postvitellogenic oocytes and mature eggs of urodele, but not anural, ascidians. It is concluded that the myoplasm of ascidian eggs contains an intermediate filament-like cytoskeletal network which is missing in anural species that have modified or eliminated the tadpole larva.
Development
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 locali...
The Journal of Physiology, 1990
Isolated blastomeres and pairs of blastomeres from 8-cell embryos of Halocynthia roretzi and Halocynthia aurantium were cleavage-arrested with cytochalasin B and cultured. Their differentiation was examined in terms of membrane excitability, immunoreactivity to an epidermis-specific monoclonal antibody (2C5), and the presence of acetylcholinesterase. 2. The blastomeres that showed epidermal-type differentiation had Ca2+dependent action potentials and membrane currents, and immunoreactivity to 2C5. The blastomeres that showed neural-type differentiation had Na+-, Ca2+and TEAsensitive delayed K+ channels, and lacked immunoreactivity to 2C5. 3. Cleavage-arrested anterior-animal blastomeres, a42, when cultured in isolation from an 8-cell embryo, differentiated exclusively into epidermal-type cells. However, when cultured in contact with anterior-vegetal blastomeres, A41, they mostly showed neural-type differentiation (seventeen out of twenty-four cells in H. roretzi). 4. Reduction of the cytochalasin B concentration enhanced neural-type development of a4-2 blastomeres in contact with A4 1 blastomeres in H. aurantium, possibly by tightening the physical contact between the blastomeres. 5. When a cleavage-arrested and isolated a4-2 blastomere was treated with 2% pronase at 10°C for 15 min at the time when sister control embryos reached the 32-cell stage, the blastomere underwent neural-type differentiation in a manner identical to that of a4 2 blastomeres contacted by A4 1 cells. 6. The period during which neural-type differentiation of a4 2blastomeres could be induced by treatment with pronase was from the 8-cell to the 110-cell stage. At the late gastrula stage neural-type differentiation of a4 2 blastomeres was not induced by pronase. The effective period for neural-type differentiation of a4 2 blastomeres in contact with A4 1 cells was between the 64-cell stage and late gastrula stage. Competence of the a4 2 blastomere to undergo neural-type differentiation decreased during gastrula stages, while the inducing ability of the A4-1 blastomere lasted longer. 7. In a few cases the posterior-animal blastomere, b4-2, could also be induced to undergo neural-type differentiation after contact with A4-1 cells or after pronase treatment. 8. The appearance of Na+ spikes in a42 blastomeres in contact with A4-1 cells was MS 7761 H. OKADO AND K. TAKAHASHI considered a manifestation of neural induction, similar in principle to the induction of ectoderm by the chorda-mesoderm in higher vertebrates.
Journal of Experimental Zoology, 1983
Acetylcholinesterase (AChE) activity has been studied in Artemia salina embryos and larvae by quantitative, histochemical, and electrophoretic methods. An AChE activity is present in dehydrated encysted gastrulae and remains low in rehydrated developing embryos, showing at hatching an increase that becomes faster during the nauplius stages (twice the gastrula activity at the nauplius I1 stage), and continues linearly in the first metanauplius stages. The histochemical staining, faint and diffuse in dehydrated gastrulae, in more advanced embryos becomes localized in cell membranes and stronger in differentiating tissues; most AChE activity is localized in the nervous and muscular cells, and a fainter one in the differentiating metanauplius segments. Dehydrated cysts show one electrophoretic AChE band, that is no longer detectable in rehydrated embryos and larvae, while two other bands appear, that migrate more slowly; in advanced larval stages, the more cathodic band is predominant. In dehydrated cysts, isoelectric focusing separates three AChE bands with isoelectric points (IP) at pH 5.0, 5.7, and 5.9; in hydrated embryos and larvae, the band at pH 5.0 is absent and another is seen at pH 5.5. Eserine, DFP, and BW284c51 inhibit the enzyme activity strongly and cause paralysis of larvae; also tubocurarine blocks the motility. These results are discussed in relation to the differentiation of the neuromuscular system and to the development of motility. As a hypothesis, in early embryonic stages, before any neuromuscular differentiation is evident, a cholinergic-like system might regulate non-neural cell activities and interactions, associated with embryogenetic events, This work is dedicated to our master, Professor Antonio Min-Address reprint requests to Dr. M Raineri, Istituto di Anato ganti.