1
|
Westbrook ER, Lenn T, Chubb JR, Antolović V. Collective signalling drives rapid jumping between cell states. Development 2023; 150:dev201946. [PMID: 37921687 PMCID: PMC10730084 DOI: 10.1242/dev.201946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 10/19/2023] [Indexed: 11/04/2023]
Abstract
Development can proceed in 'fits and starts', with rapid transitions between cell states involving concerted transcriptome-wide changes in gene expression. However, it is not clear how these transitions are regulated in complex cell populations, in which cells receive multiple inputs. We address this issue using Dictyostelium cells undergoing development in their physiological niche. A continuous single cell transcriptomics time series identifies a sharp 'jump' in global gene expression marking functionally different cell states. By simultaneously imaging the physiological dynamics of transcription and signalling, we show the jump coincides with the onset of collective oscillations of cAMP. Optogenetic control of cAMP pulses shows that different jump genes respond to distinct dynamic features of signalling. Late jump gene expression changes are almost completely dependent on cAMP, whereas transcript changes at the onset of the jump require additional input. The coupling of collective signalling with gene expression is a potentially powerful strategy to drive robust cell state transitions in heterogeneous signalling environments. Based on the context of the jump, we also conclude that sharp gene expression transitions may not be sufficient for commitment.
Collapse
Affiliation(s)
- Elizabeth R. Westbrook
- UCL Laboratory for Molecular Cell Biology and Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Tchern Lenn
- UCL Laboratory for Molecular Cell Biology and Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Jonathan R. Chubb
- UCL Laboratory for Molecular Cell Biology and Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Vlatka Antolović
- UCL Laboratory for Molecular Cell Biology and Department of Cell and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
| |
Collapse
|
2
|
Erber L, Hoffmann A, Fallmann J, Hagedorn M, Hammann C, Stadler PF, Betat H, Prohaska S, Mörl M. Unusual Occurrence of Two Bona-Fide CCA-Adding Enzymes in Dictyostelium discoideum. Int J Mol Sci 2020; 21:ijms21155210. [PMID: 32717856 PMCID: PMC7432833 DOI: 10.3390/ijms21155210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 07/20/2020] [Accepted: 07/22/2020] [Indexed: 01/12/2023] Open
Abstract
Dictyostelium discoideum, the model organism for the evolutionary supergroup of Amoebozoa, is a social amoeba that, upon starvation, undergoes transition from a unicellular to a multicellular organism. In its genome, we identified two genes encoding for tRNA nucleotidyltransferases. Such pairs of tRNA nucleotidyltransferases usually represent collaborating partial activities catalyzing CC- and A-addition to the tRNA 3'-end, respectively. In D. discoideum, however, both enzymes exhibit identical activities, representing bona-fide CCA-adding enzymes. Detailed characterization of the corresponding activities revealed that both enzymes seem to be essential and are regulated inversely during different developmental stages of D. discoideum. Intriguingly, this is the first description of two functionally equivalent CCA-adding enzymes using the same set of tRNAs and showing a similar distribution within the cell. This situation seems to be a common feature in Dictyostelia, as other members of this phylum carry similar pairs of tRNA nucleotidyltransferase genes in their genome.
Collapse
Affiliation(s)
- Lieselotte Erber
- Institute for Biochemistry, University of Leipzig, Brüderstraße 34, 04103 Leipzig, Germany; (L.E.); (H.B.)
| | - Anne Hoffmann
- Interdisciplinary Center for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107 Leipzig, Germany; (A.H.); (J.F.); (P.F.S.); (S.P.)
| | - Jörg Fallmann
- Interdisciplinary Center for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107 Leipzig, Germany; (A.H.); (J.F.); (P.F.S.); (S.P.)
| | - Monica Hagedorn
- Ribogenetics Biochemistry Lab, Department of Life Sciences and Chemistry, Jacobs University Bremen gGmbH, Campus Ring 1, 28759 Bremen, Germany; (M.H.); (C.H.)
| | - Christian Hammann
- Ribogenetics Biochemistry Lab, Department of Life Sciences and Chemistry, Jacobs University Bremen gGmbH, Campus Ring 1, 28759 Bremen, Germany; (M.H.); (C.H.)
| | - Peter F. Stadler
- Interdisciplinary Center for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107 Leipzig, Germany; (A.H.); (J.F.); (P.F.S.); (S.P.)
- German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Competence Center for Scalable Data Services and Solutions, and Leipzig Research Center for Civilization Diseases, Leipzig University, 04103 Leipzig, Germany
- Max Planck Institute for Mathematics in the Sciences, 04103 Leipzig, Germany
- Facultad de Ciencias, Universidad National de Colombia, Sede Bogotá, Carrera 45 No. 26-85, Colombia
- Santa Fe Institute for Complex Systems, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
- Department of Theoretical Chemistry of the University of Vienna, A-1090 Vienna, Austria
| | - Heike Betat
- Institute for Biochemistry, University of Leipzig, Brüderstraße 34, 04103 Leipzig, Germany; (L.E.); (H.B.)
| | - Sonja Prohaska
- Interdisciplinary Center for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107 Leipzig, Germany; (A.H.); (J.F.); (P.F.S.); (S.P.)
- Computational EvoDevo Group, Department of Computer Science, Leipzig University, Härtelstraße 16-18, 04107 Leipzig, Germany
| | - Mario Mörl
- Institute for Biochemistry, University of Leipzig, Brüderstraße 34, 04103 Leipzig, Germany; (L.E.); (H.B.)
- Correspondence: ; Tel.: +49-341-9736-911; Fax: +49-341-9736-919
| |
Collapse
|
3
|
Nichols JME, Antolović V, Reich JD, Brameyer S, Paschke P, Chubb JR. Cell and molecular transitions during efficient dedifferentiation. eLife 2020; 9:e55435. [PMID: 32255425 PMCID: PMC7190356 DOI: 10.7554/elife.55435] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 04/06/2020] [Indexed: 01/16/2023] Open
Abstract
Dedifferentiation is a critical response to tissue damage, yet is not well understood, even at a basic phenomenological level. Developing Dictyostelium cells undergo highly efficient dedifferentiation, completed by most cells within 24 hr. We use this rapid response to investigate the control features of dedifferentiation, combining single cell imaging with high temporal resolution transcriptomics. Gene expression during dedifferentiation was predominantly a simple reversal of developmental changes, with expression changes not following this pattern primarily associated with ribosome biogenesis. Mutation of genes induced early in dedifferentiation did not strongly perturb the reversal of development. This apparent robustness may arise from adaptability of cells: the relative temporal ordering of cell and molecular events was not absolute, suggesting cell programmes reach the same end using different mechanisms. In addition, although cells start from different fates, they rapidly converged on a single expression trajectory. These regulatory features may contribute to dedifferentiation responses during regeneration.
Collapse
Affiliation(s)
- John ME Nichols
- MRC Laboratory for Molecular Cell Biology and Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Vlatka Antolović
- MRC Laboratory for Molecular Cell Biology and Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Jacob D Reich
- MRC Laboratory for Molecular Cell Biology and Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | | | - Peggy Paschke
- CRUK Beatson Institute, Garscube Estate, Switchback Road, BearsdenGlasgowUnited Kingdom
| | - Jonathan R Chubb
- MRC Laboratory for Molecular Cell Biology and Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| |
Collapse
|
4
|
Roberge-White E, Katoh-Kurasawa M. Plasticity in the development and dedifferentiation of Dictyostelium discoideum. Dev Growth Differ 2011; 53:587-96. [DOI: 10.1111/j.1440-169x.2011.01256.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
5
|
Mannik J, Alzayady K, Ghazizadeh S. Regeneration of multilineage skin epithelia by differentiated keratinocytes. J Invest Dermatol 2009; 130:388-97. [PMID: 19675579 DOI: 10.1038/jid.2009.244] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although homeostasis of rapidly renewing tissues like skin epithelia is maintained by stem cells, the committed progeny of stem cells in the basal layer of epidermis retain regenerative potential and are capable of forming epidermis in response to environmental cues. It is not clear, however, at what point within the epidermal lineage keratinocytes lose this regenerative potential. In this study, we examined the extent of tissue formation by post-mitotic differentiated keratinocytes. We show that cultures of mouse keratinocytes that were, by all measures, differentiated were able to reform a self-renewing, hair-bearing skin when transplanted onto suitable sites in vivo. Genetic labeling and lineage-tracing studies in combination with an involucrin-driven Cre/lox reporter system confirmed that transplanted differentiated keratinocytes were indeed the source of the regenerated skin. More importantly, analysis of early stages of skin regeneration showed hallmarks of dedifferentiation of transplanted differentiated keratinocytes. These data indicate that commitment to differentiation does not prohibit cells from re-entering the cell cycle, de-differentiating, and acquiring "stemness". These findings suggest that epidermis can use different strategies for homeostasis and tissue regeneration.
Collapse
Affiliation(s)
- Jaana Mannik
- Department of Oral Biology and Pathology, Stony Brook University, Stony Brook, New York 11794-8702, USA
| | | | | |
Collapse
|
6
|
Geldziler B, Chatterjee I, Singson A. The genetic and molecular analysis of spe-19, a gene required for sperm activation in Caenorhabditis elegans. Dev Biol 2005; 283:424-36. [PMID: 15939418 DOI: 10.1016/j.ydbio.2005.04.036] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2004] [Revised: 04/28/2005] [Accepted: 04/28/2005] [Indexed: 11/27/2022]
Abstract
During the process of spermiogenesis (sperm activation) in Caenorhabditis elegans, the dramatic morphological events that ultimately transform round sessile spermatids into polar motile spermatozoa occur without the synthesis of any new gene products. Previous studies have identified four genes (spe-8, spe-12, spe-27 and spe-29) that specifically block spermiogenesis and lead to hermaphrodite-specific fertility defects. Here, we report the cloning and characterization of a new component of the sperm activation pathway, spe-19, that is required for fertility in hermaphrodites. spe-19 is predicted to encode a novel single-pass transmembrane protein. The spe-19 mutant phenotype, genetic interactions and the molecular nature of the gene product suggest SPE-19 to be a candidate for the receptor/co-receptor necessary for the transduction of the activation signal across the sperm plasma membrane.
Collapse
Affiliation(s)
- Brian Geldziler
- Waksman Institute, Department of Genetics, Rutgers University, Piscataway, NJ 08854, USA
| | | | | |
Collapse
|
7
|
Katoh M, Shaw C, Xu Q, Van Driessche N, Morio T, Kuwayama H, Obara S, Urushihara H, Tanaka Y, Shaulsky G. An orderly retreat: Dedifferentiation is a regulated process. Proc Natl Acad Sci U S A 2004; 101:7005-10. [PMID: 15103019 PMCID: PMC406456 DOI: 10.1073/pnas.0306983101] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Differentiation is a highly regulated process whereby cells become specialized to perform specific functions and lose the ability to perform others. In contrast, the question of whether dedifferentiation is a genetically determined process, or merely an unregulated loss of the differentiated state, has not been resolved. We show here that dedifferentiation in the social amoeba Dictyostelium discoideum relies on a sequence of events that is independent of the original developmental state and involves the coordinated expression of a specific set of genes. A defect in one of these genes, the histidine kinase dhkA, alters the kinetics of dedifferentiation and uncouples the progression of dedifferentiation events. These observations establish dedifferentiation as a genetically determined process and suggest the existence of a developmental checkpoint that ensures a return path to the undifferentiated state.
Collapse
Affiliation(s)
- Mariko Katoh
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Anjard C, Chang WT, Gross J, Nellen W. Production and activity of spore differentiation factors (SDFs) in Dictyostelium. Development 1998; 125:4067-75. [PMID: 9735367 DOI: 10.1242/dev.125.20.4067] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SDF-1 and SDF-2 are peptides that promote terminal spore differentiation under submerged conditions. The present study shows that they accumulate differentially and are released during the development of wild-type cells and can promote spore formation in cells disaggregated from wild-type culminants. SDF-1 accumulates during the slug stage and is released in a single burst at the onset of culmination while SDF-2 accumulates during early culmination and is released in a single burst from mid-culminants. The effects of SDF-1 and SDF-2 on stalk cell formation in cell monolayers were investigated. SDF-1 by itself induces stalk cell formation in some strains and also synergizes with the stalk-cell-inducing factor, DIF-1. cAMP has an inhibitory effect on stalk cell formation when either DIF-1 or SDF-1 are present on their own but is almost not inhibitory when both are present. SDF-2 alone does not induce stalk cell formation and appears to inhibit the response to DIF-1. At the same time, it increases the extent of vacuolization of the stalk cells that are produced. We propose that the release of SDF-1 and then of SDF-2 may mark irreversible steps in the developmental programme associated, respectively, with culmination and spore maturation.
Collapse
Affiliation(s)
- C Anjard
- Universität Kassel, Abt. Genetik, Heinrich-Plett-Strasse 40, D-34 132 Kassel, Germany
| | | | | | | |
Collapse
|
9
|
Hopper NA, Sanders GM, Fosnaugh KL, Williams JG, Loomis WF. Protein kinase A is a positive regulator of spore coat gene transcription in Dictyostelium. Differentiation 1995; 58:183-8. [PMID: 7713325 DOI: 10.1046/j.1432-0436.1995.5830183.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The cotA, cotB, and cotC genes encode the major spore coat proteins of Dictyostelium. All three cot genes are coordinately expressed as aggregation is nearing completion. Induction and maintenance of their expression is dependent upon the presence of extracellular cAMP. We show that expression of a dominant inhibitor of the cAMP dependent protein kinase (PKA) in prespore cells greatly reduces the transcription rates of the cotB and cotC genes. All three cot genes contain, in their upstream regulatory regions, short sequence elements that have a high content of cytosine and adenosine residues. These CA-rich sequences are essential for optimal cot gene transcription. We show that expression of the dominant PKA inhibitor results in a greatly reduced level of the binding activity that recognizes the CA-rich sequences upstream of the cotB gene. Thus PKA acts, either directly or indirectly, to control expression of the cot genes and it may do so by modulating the activity of a DNA binding protein. However, we find that mutant cells where PKA is constitutively active still require exogenous cAMP for optimal cot gene expression in dissociated cells, suggesting that a separate, PKA-independent, signalling pathway is also involved in the regulation of cot gene expression by extracellular cAMP.
Collapse
Affiliation(s)
- N A Hopper
- MRC Laboratory For Molecular Cell Biology, University College London, UK
| | | | | | | | | |
Collapse
|
10
|
Powell-Coffman JA, Firtel RA. What the papers say: Cellular dedifferentiation and spore germination inDictyostelium may utilize similar regulatory pathways. Bioessays 1993. [DOI: 10.1002/bies.950150210] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
11
|
Chandrasekhar A, Rotman M, Kraft B, Soll DR. Developmental mechanisms regulating the rapid decrease in a cohesion glycoprotein mRNA in Dictyostelium function primarily at the level of mRNA degradation. Dev Biol 1990; 141:262-9. [PMID: 2210035 DOI: 10.1016/0012-1606(90)90382-s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
During the morphogenetic program in Dictyostelium discoideum, the transcript of the gene encoding the cohesion glycoprotein gp80 accumulates to a maximum level between 4 and 6 hr, (just prior to the onset of aggregation), remains high between 6 and 10 hr (the ripple to loose aggregate stages), and then decreases to less than 10% of the maximum level between 10 and 12 hr (the tight aggregate stage). The level of gp80 transcript also decreases precipitously at the time of the erasure event in the program of dedifferentiation, or when cAMP is added to a dedifferentiating cell population prior to the erasure event. In the dedifferentiation-defective mutant HI4, the cAMP-stimulated system for rapidly reducing the level of gp80 transcript is intact, but the mechanism functioning at the time of the erasure event is defective, demonstrating that the two reduction mechanisms are dissociable. By comparing the levels of gp80 transcript with the levels of in vitro transcription of the gene in isolated nuclei, it is demonstrated that the rapid reduction of gp80 transcript immediately after aggregation and immediately after addition of 10(-4) M cAMP are the result of increased transcript degradation. The rapid reduction of gp80 transcript at the erasure event may also be due to increased transcript degradation, but transcriptional regulation cannot be completely ruled out in this case.
Collapse
|
12
|
Kraft B, Chandrasekhar A, Rotman M, Klein C, Soll DR. Dictyostelium erasure mutant HI4 abnormally retains development-specific mRNAs during dedifferentiation. Dev Biol 1989; 136:363-71. [PMID: 2555234 DOI: 10.1016/0012-1606(89)90262-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The Dictyostelium mutant HI4 progresses through morphogenesis normally, but is defective in the reverse program of dedifferentiation. In contrast to dedifferentiating wild-type cells, HI4 cells retain the capacity to rapidly reaggregate well after the "erasure event" employing a nonchemotactic aggregation mechanism involving random collisions and cohesion. They also do not lose contact sites A (gp80) at the prescribed time in the dedifferentiation program. HI4 cells accumulate transcripts of the cysteine protease gene CP2 (formerly referred to as 16G1) and the cohesion glycoprotein gene gp80 at the correct times in the morphogenetic program, but abnormally retain these transcripts at high levels well after the prescribed times at which they are lost in wild-type cells during the reverse program of dedifferentiation. The retention of these mRNAs in HI4 cells after the erasure event is not due to abnormal maintenance of a high level of intracellular cAMP during dedifferentiation. The rapid reduction in the level of gp80 transcript which can be effected by the addition of cAMP prior to the erasure event in wild-type cells is also retained by HI4 cells well after the erasure event. The results suggest that cells possess at least two mechanisms for the reduction of gp80 transcript. One involves the immediate response to cAMP and may function during the forward program of development. The second functions specifically during the reverse program of dedifferentiation. It is this latter, erasure-specific mechanism which is selectively defective in the HI4 variant.
Collapse
Affiliation(s)
- B Kraft
- Department of Biology, University of Iowa, Iowa City 52242
| | | | | | | | | |
Collapse
|
13
|
mRNA decay rates in late-developing Dictyostelium discoideum cells are heterogeneous, and cyclic AMP does not act directly to stabilize cell-type-specific mRNAs. Mol Cell Biol 1988. [PMID: 2847029 DOI: 10.1128/mcb.8.10.4088] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We reevaluated the use of 32PO4 pulse-chases for analyzing mRNA decay rates in late-developing Dictyostelium cells. We found that completely effective PO4 chases could not be obtained in developing cells and that, as a consequence, the decay rates exhibited by some mRNAs were influenced by the rates at which they were transcribed. In developing cells disaggregated in the presence of cyclic AMP, the poly(A)+ mRNA population turned over with an apparent half-life of 4 h, individual mRNA decay rates were heterogeneous, and some prestalk and prespore mRNAs appeared to decay with biphasic kinetics. In cells disaggregated in the absence of cyclic AMP, all prestalk and prespore mRNAs decayed with biphasic kinetics. During the first 1 to 1.5 h after disaggregation in the absence of cyclic AMP, the cell-type-specific mRNAs were selectively degraded, decaying with half-lives of 20 to 30 min; thereafter, the residual prestalk and prespore mRNA molecules decayed at rates that were similar to those measured in the presence of cyclic AMP. This short-term labilization of cell-type-specific mRNAs was observed even for those species not requiring cyclic AMP for their accumulation in developing cells. The observation that cell-type specific mRNAs can decay at similar rates in disaggregated cells with or without cyclic AMP indicates that this compound does not act directly to stabilize prestalk and prespore mRNAs during development and that its primary role in the maintenance of cyclic-AMP-dependent mRNAs is likely to be transcriptional.
Collapse
|
14
|
Manrow RE, Jacobson A. mRNA decay rates in late-developing Dictyostelium discoideum cells are heterogeneous, and cyclic AMP does not act directly to stabilize cell-type-specific mRNAs. Mol Cell Biol 1988; 8:4088-97. [PMID: 2847029 PMCID: PMC365478 DOI: 10.1128/mcb.8.10.4088-4097.1988] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We reevaluated the use of 32PO4 pulse-chases for analyzing mRNA decay rates in late-developing Dictyostelium cells. We found that completely effective PO4 chases could not be obtained in developing cells and that, as a consequence, the decay rates exhibited by some mRNAs were influenced by the rates at which they were transcribed. In developing cells disaggregated in the presence of cyclic AMP, the poly(A)+ mRNA population turned over with an apparent half-life of 4 h, individual mRNA decay rates were heterogeneous, and some prestalk and prespore mRNAs appeared to decay with biphasic kinetics. In cells disaggregated in the absence of cyclic AMP, all prestalk and prespore mRNAs decayed with biphasic kinetics. During the first 1 to 1.5 h after disaggregation in the absence of cyclic AMP, the cell-type-specific mRNAs were selectively degraded, decaying with half-lives of 20 to 30 min; thereafter, the residual prestalk and prespore mRNA molecules decayed at rates that were similar to those measured in the presence of cyclic AMP. This short-term labilization of cell-type-specific mRNAs was observed even for those species not requiring cyclic AMP for their accumulation in developing cells. The observation that cell-type specific mRNAs can decay at similar rates in disaggregated cells with or without cyclic AMP indicates that this compound does not act directly to stabilize prestalk and prespore mRNAs during development and that its primary role in the maintenance of cyclic-AMP-dependent mRNAs is likely to be transcriptional.
Collapse
Affiliation(s)
- R E Manrow
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655
| | | |
Collapse
|
15
|
|
16
|
Varnum-Finney BJ, Voss E, Soll DR. Frequency and orientation of pseudopod formation of Dictyostelium discoideum amebae chemotaxing in a spatial gradient: further evidence for a temporal mechanism. CELL MOTILITY AND THE CYTOSKELETON 1987; 8:18-26. [PMID: 2820592 DOI: 10.1002/cm.970080104] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Amebae of Dictyostelium discoideum normally chemotax to aggregation centers by assessing the direction of outwardly moving, nondissipating waves of the chemoattractant cAMP. However, D. discoideum amebae can also assess the direction of a relatively stable spatial gradient. We demonstrate that amebae migrating towards the "source" of a stable, spatial gradient move faster, extend fewer pseudopodia, and turn less frequently than amebae migrating away from the "source" in the same spatial gradient. In addition, amebae extend lateral pseudopods in a polarized fashion from the anterior half of the cell, and do so as frequently towards the source as away from the source. However, those formed towards the source more often produce a turn than those formed away from the source. These results suggest that there may be two decision-making systems, one localized in the pseudopods, and one along the entire cell body; they support the suggestion that Dictyostelium amebae may employ a temporal mechanism to assess the direction of a spatial gradient of chemoattractant.
Collapse
|