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  • 1
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cellular dedifferentiation is an important developmental response to perturbations in morphogenesis. In the cellular slime mold Dictyostelium discoideum this process gives cells the flexibility, when multicellular development is disrupted, to respond to nutrients and reinitiate vegetative growth. Recent studies in D. discoideum described by Soll and colleagues(1) show that genes previously thought to be expressed only during spore germination are also expressed during induced dedifferentiation, suggesting that similar molecular mechanisms are involved in these two developmental processes. It should now be possible to determine whether the developmental programs that control dedifferentiation during spore germination also control conversion of cell types in the multicellular organism.
    Additional Material: 1 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 9 (1988), S. 337-350 
    ISSN: 0192-253X
    Keywords: Dictyostelium ; cAMP ; receptor ; gene regulation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have examined the expression of a cAMP pulse-repressed and two cAMP pulse-induced genes in response to cAMP and caffeine under a number of different physiological conditions, and in several classes of developmental mutants altered in cAMP-mediated signal transduction pathways. The data presented help characterize the mutants with regard to early gene expression. Analysis of the data indicates that full induction of the pulse-induced or repression of the pulse-repressed genes requires cycles of activation and adaptation of the cAMP receptor but does not require a rise in intracellular cAMP. Comparison of the results obtained between different mutant classes suggests that repression and activation of the two classes of genes can be uncoupled, implying that different intracellular mechanisms control these processes. In addition, we examined the effects of caffeine and show that it can induce pulse-induced mRNA accumulation in the absence of cAMP.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 9 (1988), S. 435-454 
    ISSN: 0192-253X
    Keywords: cis-acting sequences ; trans-acting factors ; gene regulation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Expression of the Dictyostelium discoideum pst-cath (CP2) gene is transcriptionally regulated during multicellular development, and the gene is inducible in competent single cells following administration of exogenous cAMP. The 5′ flanking region of pst-cath (CP2) that extends from -313 to the Cap site (+-1) has previously been shown to contain sufficient cis,-acting regulatory elements for proper developmental and cAMP-inducible expression of a foreign gene [Datta and Firtel, 1987, Mol Cell Biol 7:149-159]. The -283 to -201 region includes two exceptional “G-boxes” centered at -233 and -217 respectively, and this ∼ 80 bp region is essential for basal as well as regulated expression of the pst-cath (CP2) gene. Here we summarize results obtained from a detailed analysis of a series of linker-scanner mutants and mutants that carry small internal deletions within the essential 80-bp region. Insertion of a synthetic oligonucleotide that includes the downstream G-box is demonstrated to rescue a low level of cAMP-inducible expression following insertion into cassette mutants. The effect of introducing a change in the relative spacing between regulatory elements has also been investigated.We have analyzed nuclear extracts for the presence of DNA-binding proteins that interact specifically with the pst-cath (CP2) regulatory region and identified two such putative trans-acting factors: (1) the AT-factor that is observed within a few hours following the onset of starvation and that binds tightly to stretches of alternating adenine-thymine residues (poly(dA-dT)); and (2) the AG-factor that is present in nuclear extracts of aggregated cells. Competition studies have demonstrated significant differences in the affinity that characterizes the binding of the two factors to G-box-containing sequences. The binding specificities of these DNA-binding proteins have been analyzed using gel mobility-shift and DNaseI footprinting assays.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 7 (1986), S. 99-108 
    ISSN: 0192-253X
    Keywords: cell-cell contact ; development ; prestalk ; prespore ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have analyzed the expression of a series of developmentally regulated genes in the Dictyostelium discoideum strain JC-5. This strain has been previously described as a temperature-sensitive, cohesion-defective derivative of FR17, itself a temporally deranged mutant of wild-type NC-4. At restrictive temperature (27°C), JC-5 initially acquires EDTA-resistant cell contacts but at the time of tip formation (12 hr) loses the ability to make specific cell-cell associations and regresses to an amorphous mound of cells. We have found that genes preferentially expressed in either prespore or prestalk cells are expressed prior to the appearance of the cohesion defect in JC-5; the specific cell contact system defective in this strain is necessary for neither the proper initiation nor maintenance of expression of either prespore of prestalk genes. We have also found, by use of an in vitro cell suspension system, that JC-5 is temperature-sensitive with respect to gene expression several hours before the defect in cell cohesion is observable. Our data suggest that the defect in JC-5 is due to a specific lesion not in the late cohesion system but rather in a more general component that is required earlier in the developmental process.
    Additional Material: 3 Ill.
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