Use of Alu Element Containing Minigenes to Analyze Circular RNAs
March 10th, 2020
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We clone and analyze reporter genes generating circular RNAs. These reporter genes are larger than constructs to analyze linear splicing and contain Alu elements. To investigate the circular RNAs, the constructs are transfected into cells and resulting RNA is analyzed using RT-PCR after removal of linear RNA.
Overview
This protocol enables the generation of circular RNAs through a genomic expression system that allows for alternative splicing. It provides a method for testing the function and disease association of these circular RNAs.
Key Study Components
Area of Science
- Molecular Biology
- Cloning Techniques
- RNA Biology
Background
- Circular RNAs are important for understanding gene regulation.
- Alternative splicing contributes to the diversity of RNA molecules.
- Alu elements play a role in the formation of circular RNAs.
- RT-PCR is a common method for analyzing RNA.
Purpose of Study
- To develop a protocol for generating circular RNAs.
- To investigate the function and disease relevance of these RNAs.
- To provide a visual representation of the procedure for better understanding.
Methods Used
- Cloning of reporter genes containing Alu elements.
- Transfection of constructs into cells.
- RT-PCR for RNA analysis after linear RNA removal.
- Optimization of PCR conditions for effective amplification.
Main Results
- Successful generation of circular RNAs from the constructs.
- Demonstration of effective PCR conditions for longer fragments.
- Visual aids provided for complex aspects of the protocol.
- Potential applications in studying alternative splicing.
Conclusions
- This technique enhances the understanding of circular RNA formation.
- It serves as a valuable tool for molecular biology research.
- Future studies can leverage this protocol for various applications.
Frequently Asked Questions
What are circular RNAs?
Circular RNAs are a type of RNA that forms a covalently closed loop, which can play roles in gene regulation and disease.
How does this protocol improve RNA analysis?
It allows for the generation of circular RNAs that can be analyzed for their function and association with diseases.
What is the significance of Alu elements in this study?
Alu elements are important for the formation of circular RNAs and are included in the reporter gene constructs.
What optimization tips are provided for PCR?
It is recommended to run gradients or perform touchdown PCR with varying annealing temperatures and extension times.
Why is visual representation important in this protocol?
Visual aids help users understand complex steps, particularly in generating primers and executing the protocol.
Executive Industry Relevance
This method enables the generation of circular RNA expression systems to study RNA processing mechanisms relevant to neurodegenerative disease pathways. By incorporating Alu elements into reporter constructs, researchers can model back-splicing events and identify regulatory factors influencing circular RNA biogenesis. The approach supports target validation and mechanistic de-risking in early discovery by linking RNA biology to disease-associated phenotypes such as tauopathies.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of RNA sequence elements and cellular components involved in circular RNA formation.
- Operational Value: Supports functional target validation by linking splicing factor expression (e.g., CLK2, 9G8) to circular RNA output.
- Predictive Value: Facilitates hypothesis testing of RNA-mediated disease mechanisms, aiding in target confidence assessment.
Screening & Assay Development
- Scientific Value: Generates quantitative RT-PCR readouts after RNase R treatment to distinguish circular from linear RNA isoforms.
- Operational Value: Enables standardized co-transfection assays for screening splicing factor impact on circular RNA yield.
- Scalability: Optimized PCR and cloning protocols allow for constructs up to 20 kb, supporting high-throughput screening readiness.
Translational & Preclinical Research
- Translational Relevance: Models disease-relevant circular RNA expression in human cells (HEK293) using tau minigene constructs.
- Mechanistic De-risking: Identifies splicing regulators (CLK2, 9G8) as potential biomarkers or modulators in tau pathology.
- Preclinical Continuity: Supports functional follow-up studies such as protein sequestration or translation assays to assess circular RNA role in disease.
Pipeline & Workflow Integration
The method fits within the discovery-to-preclinical continuum by enabling hypothesis-driven analysis of RNA processing events that influence target validity and pathway modulation.
- Discovery Biology: Tests how Alu-mediated RNA structures promote back-splicing and circular RNA generation.
- Screening: Produces reproducible, quantifiable circular RNA signals post-RNase R treatment for comparative condition analysis.
- Analytics: Uses RT-PCR with circular-specific primers and RNase R sensitivity to provide specific, measurable outputs.
- Translational Research: Connects circular tau RNA expression to splicing factor levels observed in human brain tissue models.
- Enterprise Reuse: Provides a modular minigene platform adaptable to other genes and species for circular RNA functional screening.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in RNA regulation by isolating circular RNA biogenesis from linear splicing events.
- Operational Value: Standardized cloning, transfection, and RNA analysis workflows improve reproducibility across teams.
- Strategic Value: Informs go/no-go decisions by linking RNA processing factors to disease-associated RNA isoforms.
- Portfolio Impact: Enables risk-adjusted prioritization of targets based on RNA-mediated pathway validation.
Implementation Considerations
- Requires expertise in molecular cloning, primer design outside repetitive elements, and PCR optimization for long fragments.
- Dependent on access to genomic databases (UCSC Genome Browser) and tools for identifying Alu element orientation and intron/exon boundaries.
- Necessitates standardized RNA isolation and RNase R treatment protocols to ensure specific circular RNA detection.
- Requires optimization of annealing temperatures and extension times for fragments over 6 kb, with validation via dual gel electrophoresis (agarose + ethidium bromide).
- Limited by primer design constraints—primers must avoid repetitive regions to ensure specific amplification, increasing development time for complex loci.
Biopharma FAQs
Why does RNase R treatment matter for circular RNA validation?
RNase R degrades linear RNA while sparing circular RNAs, enabling specific detection of back-spliced isoforms. This distinction is critical for confirming circular RNA generation in transfection experiments and avoiding false positives from linear transcripts or splicing artifacts.
How does primer design outside repetitive elements improve target validation?
Primers placed in unique exonic regions prevent non-specific amplification from repetitive Alu sequences, ensuring accurate quantification of the intended circular RNA product. This improves assay specificity and supports reliable assessment of splicing factor dependence in functional studies.
What quantitative measurements enable splicing factor dependency analysis?
RT-PCR amplification of circular RNA using isoform-specific primers, followed by RNase R treatment, provides a quantitative readout of circular RNA levels. Changes in band intensity upon overexpression of factors like CLK2 or 9G8 indicate regulatory influence on back-splicing efficiency.
Why do replication requirements matter for cross-functional collaboration?
Consistent circular RNA detection across replicates ensures that observed dependencies on splicing factors are robust and not due to transfection or PCR variability. This reliability supports data sharing between discovery, assay development, and translational teams for target validation.
What statistical analysis capabilities are required before implementation?
Comparative analysis of circular RNA signal intensity across conditions (e.g., control vs. splicing factor overexpression) requires normalization and statistical testing to determine significant changes. Basic quantitative comparison of RT-PCR bands enables assessment of regulatory impact without complex modeling.
Chapters in this video
0:05
Introduction
1:09
Design of the Constructs
2:14
Select the Sequence to be Cloned in an Expression Vector
3:35
Design Primers for Cloning
4:59
Cloning of Constructs
7:05
Transfection of the Reporter Genes into Eukaryotic Cells
10:21
Results: Analysis of Circular RNAs
11:09
Conclusion
