Quantitative regulation of acetylcholinesterase development in the muscle lineage cells of cleavage-arrested ascidian embryos

Development ◽  
1983 ◽  
Vol 76 (1) ◽  
pp. 235-250
Author(s):  
J. R. Whittaker
Keyword(s):  
Cytochrome Oxidase ◽  
Translational Control ◽  
Development Time ◽  
Muscle Development ◽  
Acetylcholinesterase Activity ◽  
Control Mechanisms ◽  
Ascidian Embryos ◽  
Nuclear Number ◽  
Cytoplasmic Determinant ◽  
Cytoplasmic Determinants

Some embryos of Ciona intestinalis which were permanently cleavage-arrested with cytochalasin B at the 1-cell, 4-cell, or 8-cell stages produced, after 12 or 16 h of development time (18 °C), a level of muscle acetylcholinesterase activity equal to that found in normal early and later larval stage embryos of the same age. Enzyme activity was measured quantitatively in single whole embryos by a colorimetric procedure using microdensitometry. Quantitative regulation of a differentiation end product indicated that the usual transcriptional and translational control mechanisms for that histospecific protein continued to operate normally in the cleavage-arrested embryos. Acetylcholinesterase expression was apparently regulated independently of the usual cell cytoplasmic volume in the muscle lineage cells and possibly also independently of the normal nuclear number in the lineage. There is an egg cytoplasmic determinant that is segregated into the muscle lineage cells during cleavage and which appears to specify the pathway of larval muscle development. Quantitative control of muscle acetylcholinesterase is possibly one of the consequences of how the agent releases genetic expression in the presumptive muscle cells. Quantitative regulation was not, however, a general functional activity of cleavage-arrested embryos. Mitochondrial cytochrome oxidase, an enzyme whose development is believed to be unaffected by cytoplasmic determinants, was not regulated quantitatively in cleavage-arrested embryos. Cytochrome oxidase activity of cleavage-arrested embryos, measured in single whole embryos by a colorimetric microdensitometry assay, increased only slightly during 16 h of development time whereas the activity in normal control embryos doubled during that time.

Determinative properties of muscle lineages in ascidian embryos

Development ◽  
1987 ◽  
Vol 100 (2) ◽  
pp. 245-260 ◽  
Author(s):  
T.H. Meedel ◽  
R.J. Crowther ◽  
J.R. Whittaker
Keyword(s):  
Muscle Development ◽  
Tail Length ◽  
Muscle Cells ◽  
Acetylcholinesterase Activity ◽  
Cell Interactions ◽  
Animal Cells ◽  
Early Cleavage ◽  
Cell Lineages ◽  
Larval Muscle ◽  
Ascidian Embryos

Blastomeres removed from early cleavage stage ascidian embryos and reared to ‘maturity’ as partial embryos often elaborate tissue-specific features typical of their constituent cell lineages. We used this property to study recent corrections of the ascidian larval muscle lineage and to compare the ways in which different lineages give rise to muscle. Our evaluation of muscle differentiation was based on histochemical localization and quantitative radiometric measurement of a muscle-specific acetylcholinesterase activity, and the development of myofilaments and myofibrils as observed by electron microscopy. Although the posterior-vegetal blastomeres (B4.1 pair) of the 8-cell embryo have long been believed to be the sole precursors of larval muscle, recent studies using horseradish peroxidase to mark cell lineages have shown that small numbers of muscle cells originate from the anterior-vegetal (A4.1) and posterior-animal (b4.2) blastomeres of this stage. Fully differentiated muscle expression in isolated partial embryos of A4.1-derived cells requires an association with cells from other lineages whereas muscle from B4.1 blastomeres develops autonomously. Clear differences also occurred in the time acetylcholinesterase activity was first detected in partial embryos from these two sources. Isolated b4.2 cells failed to show any muscle development even in combination with anterior-animal cells (a4.2) and are presumably even more dependent on normal cell interactions and associations. Others have noted an additional distinction between the different sources of muscle: muscle cells from non-B4.1 lineages occur exclusively in the distal part of the tail, while the B4.1 descendants contribute those cells in the proximal and middle regions. During the course of ascidian larval evolution tail muscle probably had two origins: the primary lineage (B4.1) whose fate was set rigidly at early cleavage stages and secondarily evolved lineages which arose later by recruitment of cells from other tissues resulting in increased tail length. In contrast to the B4.1 lineage, muscle development in the secondary lineages is controlled less rigidly by processes that depend on cell interactions.

scholarly journals A UV-Induced Mutation in Neurospora That Affects Translational Regulation in Response to Arginine

Genetics ◽  
1996 ◽  
Vol 142 (1) ◽  
pp. 117-127 ◽  
Author(s):  
Michael Freitag ◽  
Nelima Dighde ◽  
Matthew S Sachs
Keyword(s):  
Translational Control ◽  
Translational Regulation ◽  
Fusion Gene ◽  
Mrna Translation ◽  
Small Subunit ◽  
Upstream Open Reading Frame ◽  
Control Mechanisms ◽  
Carbamoyl Phosphate ◽  
Altered Expression ◽  
Reading Frame

The Neurospora crmsu arg-2 gene encodes the small subunit of arginine-specific carbamoyl phosphate synthetase. The levels of arg-2 mRNA and mRNA translation are negatively regulated by arginine. An upstream open reading frame (uORF) in the transcript’s 5′ region has been implicated in arginine-specific control. An arg-2-hph fusion gene encoding hygromycin phosphotransferase conferred arginine-regulated resistance to hygromycin when introduced into N. crassa. We used an arg-2-hph strain to select for UV-induced mutants that grew in the presence of hygromycin and arginine, and we isolated 46 mutants that had either of two phenotypes. One phenotype indicated altered expression of both arg-2-hph and urg-2 genes; the other, altered expression of urg-2-hph but not arg-2. One of the latter mutations, which was genetically closely linked to arg-2-hph, was recovered from the 5′ region of the arg-2-hph gene using PCR. Sequence analyses and transformation experiments revealed a mutation at uORF codon 12 (Asp to Asn) that abrogated negative regulation. Examination of the distribution of ribosomes on arg-2-hph transcripts showed that loss of regulation had a translational component, indicating the uORF sequence was important for Arg-specific translational control. Comparisons with other uORFS suggest common elements in translational control mechanisms.

scholarly journals Polyamine Regulation of Ornithine Decarboxylase Synthesis in Neurospora crassa

2000 ◽  
Vol 20 (8) ◽  
pp. 2760-2773 ◽  
Author(s):  
Martin A. Hoyt ◽  
Mariya Broun ◽  
Rowland H. Davis
Keyword(s):  
Neurospora Crassa ◽  
Ornithine Decarboxylase ◽  
Dna Sequences ◽  
Translational Control ◽  
Control Mechanisms ◽  
Coding Region ◽  
Polyamine Biosynthesis ◽  
Rate Limiting Step ◽  
Sequence Elements ◽  
Rate Limiting

ABSTRACT Ornithine decarboxylase (ODC) of the fungus Neurospora crassa, encoded by the spe-1 gene, catalyzes an initial and rate-limiting step in polyamine biosynthesis and is highly regulated by polyamines. In N. crassa, polyamines repress the synthesis and increase the degradation of ODC protein. Changes in the rate of ODC synthesis correlate with similar changes in the abundance of spe-1 mRNA. We identify two sequence elements, one in each of the 5′ and 3′ regions of the spe-1 gene ofN. crassa, required for this polyamine-mediated regulation. A 5′ polyamine-responsive region (5′ PRR) comprises DNA sequences both in the upstream untranscribed region and in the long 5′ untranslated region (5′-UTR) of the gene. The 5′ PRR is sufficient to confer polyamine regulation to a downstream, heterologous coding region. Use of the β-tubulin promoter to drive the expression of various portions of the spe-1 transcribed region revealed a 3′ polyamine-responsive region (3′ PRR) downstream of the coding region. Neither changes in cellular polyamine status nor deletion of sequences in the 5′-UTR alters the half-life of spe-1 mRNA. Sequences in the spe-1 5′-UTR also impede the translation of a heterologous coding region, and polyamine starvation partially relieves this impediment. The results show that N. crassa uses a unique combination of polyamine-mediated transcriptional and translational control mechanisms to regulate ODC synthesis.

Understanding translational control mechanisms of the mTOR pathway in CHO cells by polysome profiling

2014 ◽  
Vol 31 (5) ◽  
pp. 514-523 ◽  
Author(s):  
Franck C. Courtes ◽  
Leah Vardy ◽  
Niki S.C. Wong ◽  
Muriel Bardor ◽  
Miranda G.S. Yap ◽  
...  
Keyword(s):  
Translational Control ◽  
Cho Cells ◽  
Mtor Pathway ◽  
Control Mechanisms ◽  
Polysome Profiling

T7 Translational Control Mechanisms and their Inhibition by F Factors

1971 ◽  
Vol 231 (19) ◽  
pp. 37-41 ◽  
Author(s):  
TRUDY G. MORRISON ◽  
MICHAEL H. MALAMY
Keyword(s):  
Translational Control ◽  
Control Mechanisms
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