A

Area of Science:

• Molecular Genetics
• Developmental Biology
• Gene Editing Technologies

Background:

• Precise spatial and temporal control of gene function is crucial in molecular genetics.
• Standard CRISPR-Cas9 methods, like Gal4-mediated overexpression, can cause lethality and developmental issues, particularly in tissues like the Drosophila prothoracic gland (PG).
• There's a need for tools to validate RNA interference (RNAi) phenotypes specifically in the PG.

Purpose of the Study:

• To develop modular, gateway-compatible CRISPR-Cas9 tools for precise temporal and spatial gene modulation.
• To overcome limitations of existing Cas9 expression systems, such as lethality, in specific tissues like the PG.
• To provide tools for both gain- and loss-of-function studies in endoreplicating cells.

Main Methods:

• Development of modular, gateway-compatible CRISPR-Cas9 toolkits.
• Fusion of Cas9 to a progesterone ligand-binding domain for RU486-inducible gene activation.
• Testing the tools in the Drosophila prothoracic gland (PG), a polytene tissue.

Main Results:

• The developed CRISPR-Cas9 tools enable precise temporal and spatial control of gene activity.
• Cas9 fused to the progesterone ligand-binding domain allows for RU486-inducible gene activation.
• These new approaches avoid the lethality associated with simple Gal4-mediated Cas9 overexpression in the PG, demonstrating efficacy in endoreplicating cells.

Conclusions:

• The presented CRISPR-Cas9 toolkit offers precise control over gene function with temporal and spatial specificity.
• The tools are effective in endoreplicating cells, such as those in the Drosophila PG, and can be adapted for other tissues.
• This toolkit facilitates both gain- and loss-of-function studies, addressing a critical need in developmental genetics.