Cell aggregation and Differentiation in Dictyostelium.pptx

Cell aggregation and Differentiation in Dictyostelium -Dr.M.Jothimuniyandi -Dictyostelium-Starvation Signal-Chemotaxis-Formation of Aggregates-Development of the Slug-Migration of the Slug-SLIME MODELS-Prespore Cells-Prestalk Cells-life cycle - Cell Fate Decisions-Gene Regulation-importance-Signal transduction-Developmental biology-Apoptosis-Social behavior.

1. CELL AGGREGATION AND DIFFERENTIATION IN DICTYOSTELIUM Dr.M.JOTHIMUNIYANDI

2. Dictyostelium Dictyostelium is a simple eukaryotic model system that is widely used  to study essential cell biological processes such as cell division, chemotactic cell movement and pattern formation in the felid of developmental biology . Dictyostelium discoideum is a species of soil-dwelling amoeba belonging to the phylum Amoebozoa , commonly referred to as slime mold, D. discoideum is a eukaryote that transitions from a collection of unicellular amoebae into a multicellular slug and then into a fruiting body within its lifetime.

3. Cell aggregation Dictyostelium discoideum is a remarkable process that transforms single-celled amoebae into a complex multicellular structure. Process of Cell Aggregation 1. Starvation Signal: - Nutrient Deprivation: When the amoebae in the soil experience a lack of food (bacteria), they initiate a developmental response. cAMP Secretion: The cells begin to secrete cyclic AMP ( cAMP ), a signaling molecule that acts as a chemotactic signal to coordinate the behavior of other cells.

4. Cell aggregation 2.Chemotaxis: - Movement t oward cAMP : Cells respond to the cAMP gradient by moving toward higher concentrations of this signaling molecule. This movement is called chemotaxis. Cell Clustering: As cells migrate, they aggregate into a large, dense cluster. This aggregation is the initial step toward forming a multicellular structure.

5. Cell aggregation 3. Formation of Aggregates: - Cell Adhesion: Cells adhere to one another through surface proteins and adhesion molecules. This adhesion is crucial for maintaining the structure of the aggregate. Formation of a Loose Aggregate: The first stage of aggregation results in a loose cluster of cells.

6. Cell aggregation 4. Development of the Slug: Further Aggregation: The loose aggregate transitions into a more organized structure known as the slug or pseudoplasmodium . Cell Differentiation: Within the slug, cells start to differentiate into different types that will contribute to the formation of the fruiting body.

7. Cell aggregation 5. Migration of the Slug: Directional Movement: The slug moves as a cohesive unit towards more favorable conditions, often guided by environmental cues like light or gravity. Organizational Structure: The slug has a defined anterior (front) and posterior (rear) end, with cells at the front being more mobile and those at the rear being less so

8. Importance of Cell Aggregation The aggregation process in Dictyostelium provides insights into the evolution of multicellularity and cooperative behavior among cells. Study of Cellular Communication: It offers a model system to study how cells communicate and coordinate their activities in response to environmental changes. Mechanisms of Development: Understanding cell aggregation helps in exploring broader mechanisms of developmental biology and tissue formation. Cell aggregation in Dictyostelium discoideum is a highly regulated and dynamic process involving chemotaxis, cell signaling, and adhesion. This process transitions from individual amoebae to a multicellular slug, showcasing how cells can coordinate to form complex structures in response to environmental signals.

9. SLIME MODELS

10. CELL Differentiation After aggregation, the slug moves to an optimal location before differentiating into specialized cells that form the fruiting body. This process involves two major types of differentiation : Prespore Cells: Around 80% of the cells in the slug differentiate into prespore cells , which will form spores. These spores are designed to survive harsh conditions and can germinate into new amoebae when the environment becomes favorable again . Prestalk Cells: About 20% of the cells differentiate into prestalk cells , which will form the stalk of the fruiting body. These cells die during the process, sacrificing themselves to support the spores, which are elevated for better dispersion.

11. The life cycle of  Dictyostelium discoideum Reference: Maeda Y, Chida J. Control of Cell Differentiation by Mitochondria, Typically Evidenced in  Dictyostelium  Development.  Biomolecules . 2013; 3(4):943-966. https://doi.org/10.3390/biom3040943

12. Regulation of Differentiation Cell Fate Decisions : Cells differentiate into prestalk or prespore cells based on positional cues, gene expression patterns, and environmental signals . Differentiation-inducing factors (DIFs) play an essential role in determining whether a cell becomes a prestalk cell. Gene Regulation : Several genes are activated or repressed during differentiation, including those regulating prestalk and prespore differentiation. These genes include transcription factors like GBF (G-box binding factor) that control the expression of prespore genes, and STATc , which is involved in prestalk gene expression.

13. Fruiting Body Formation After the slug migrates to a suitable environment, it undergoes a process called culmination : Stalk Formation: The prestalk cells form the elongated stalk, sacrificing themselves to provide structural support for the fruiting body. Spore Formation: The prespore cells are carried upward by the stalk, forming a spore head at the top. These spores are resistant to adverse conditions and can germinate to form new amoebae when favorable conditions return.

14. Importance of Dictyostelium in Research The differentiation process in Dictyostelium is a valuable model for studying: Signal transduction : How cells respond to external signals like cAMP . Developmental biology : Mechanisms of cell fate determination and pattern formation. Apoptosis : Programmed cell death involved in the formation of the stalk. Social behavior : How individual cells cooperate to form a multicellular organism. This system serves as a bridge between simple unicellular organisms and more complex multicellular development.

15. Thank you Reference: https://www.cronodon.com/BioTech/Dictyostelium.html