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Cyclic AMP and NH3/NH4+ both regulate cell-type-specific mRNA accumulation in the cellular slime mold, Dictyostelium
Abstract:
Dictyostelium discoideum cells plated for development until aggregation stage, and then dissociated into media containing glucose, albumin, and cAMP will form into clumps and undergo prespore and prestalk differentiation. Differentiation in this in vitro system is dependent on three components: cAMP, multicellularity, and the acquisition of "differentiation competence" which the cells acquire in a period between interphase and aggregation stage when plated on Millipore filters. We have used this system to explore aspects of the multicellular environment which are involved in regulation the accumulation of the different prespore- and prestalk-specific messenger RNAs. Two classes of prespore messenger RNA, as well as a prestalk-specific messenger RNA, all require the acquisition of differentiation competence in order to be expressed in response to cAMP. Additionally, all of these messenger RNAs require agglomerate formation for maximal expression. The addition of 33 mM ammonium sulfate (NH4)2SO4, however, can entirely replace the requirement for agglomerate formation for expression of the prestalk-specific messenger RNA, and can partially substitute for agglomerate formation in inducing the expression of both classes of prespore-specific messenger RNAs. In this system, cAMP is essential for the initial induction of expression of all three classes of messenger RNAs. In this system, cAMP is essential for the initial induction of expression of all three classes of messenger RNAs while agglomerate formation or elevated NH3/NH+4 is essential only for the maintenance of the elevated levels of the messenger RNAs.
Insights
Dictyostelium discoideum differentiation into prespore and prestalk cells requires cyclic adenosine monophosphate (cAMP) and multicellularity. Ammonium sulfate can substitute for cell aggregation in regulating messenger RNA accumulation during differentiation.
Area of Science:
- Cellular and Molecular Biology
- Developmental Biology
- Biochemistry
Background:
- Dictyostelium discoideum serves as a model organism for studying cellular differentiation.
- Cell differentiation into prespore and prestalk fates is regulated by cyclic adenosine monophosphate (cAMP) and cell-cell interactions.
- Understanding the molecular mechanisms governing differentiation is crucial for developmental biology.
Purpose of the Study:
- To investigate the role of multicellularity and environmental factors in regulating gene expression during Dictyostelium discoideum differentiation.
- To identify the specific components required for the induction and maintenance of prespore- and prestalk-specific messenger RNA accumulation.
- To explore the potential of exogenous substances, like ammonium sulfate, to influence differentiation pathways.
Main Methods:
- Utilizing an in vitro system where Dictyostelium discoideum cells are induced to differentiate.
- Manipulating cell aggregation and introducing cyclic adenosine monophosphate (cAMP) and ammonium sulfate to observe effects on gene expression.
- Quantifying the accumulation of specific prespore- and prestalk-messenger RNAs in response to experimental conditions.
Main Results:
- Expression of prespore and prestalk messenger RNAs requires both differentiation competence and cyclic adenosine monophosphate (cAMP).
- Maximal messenger RNA expression is dependent on cell agglomerate formation.
- Ammonium sulfate can replace or partially substitute for cell aggregation in regulating messenger RNA accumulation, particularly for prestalk-specific transcripts.
Conclusions:
- Cyclic adenosine monophosphate (cAMP) is essential for the initial induction of differentiation-specific gene expression.
- Multicellularity, or factors mimicking its effect like ammonium sulfate, is crucial for maintaining elevated levels of these messenger RNAs.
- This study elucidates key regulatory factors in Dictyostelium discoideum differentiation, offering insights into developmental processes.