Identification of pathways regulating cell size and cell-cycle progression by RNAi

Area of Science:

• Cell Biology
• Genetics
• Developmental Biology

Background:

• Eukaryotic cell cycle research has largely used yeast models (Saccharomyces cerevisiae, Schizosaccharomyces pombe).
• Multicellular organisms possess additional cell cycle control mechanisms essential for organismal and organ size regulation.

Purpose of the Study:

• To identify genes regulating cell-cycle progression in a multicellular context.
• To uncover novel pathways controlling cell size, cytokinesis, cell death, and cell cycle phases (G1, G2/M) in Drosophila S2 cells.

Main Methods:

• Performed high-throughput loss-of-function analysis on 70% of Drosophila genes, including 90% of human-conserved genes.
• Utilized flow cytometry to assess cell-cycle progression phenotypes.
• Investigated gene redundancy by simultaneously targeting homologous genes involved in protein phosphorylation.

Main Results:

• Identified genes critical for cell size, cytokinesis, cell death/apoptosis, and cell cycle phases (G1, G2/M).
• Unsupervised hierarchical clustering revealed that cell-cycle progression is controlled by classical regulators (Myc/Max, Cyclin/Cdk, E2F) and novel pathways including vesicular/nuclear transport, COP9 signalosome, and Wnt, p38betaMAPK, FRAP/TOR, JAK/STAT signaling.
• Discovered a translational regulator, eIF-3p66, specifically impacting Cyclin/Cdk pathway activity.

Conclusions:

• Drosophila S2 cells provide a valuable model for studying multicellular cell-cycle regulation.
• Cell-cycle control involves a complex network integrating classical pathways with transport mechanisms and extracellular signaling.
• Identified eIF-3p66 as a novel regulator of the Cyclin/Cdk pathway.