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MapR R-Loop Sequencing Service: Low-Input & Rapid Profiling

Overcome sample limitations with our MapR R-Loop Sequencing Service. This rapid, antibody-free method utilizes a recombinant RNase H-MNase fusion protein to map R-loops in situ with exceptional sensitivity and resolution. Ideal for rare cell populations, clinical samples, and researchers seeking a high-fidelity alternative to standard DRIP-seq. RUO.

  • Low Input: Compatible with <50,000 cells or rare primary samples.
  • Antibody-Free: Uses RNase H specificity to eliminate S9.6 off-target noise.
  • High Resolution: MNase-mediated cleavage delivers sharp, precise R-loop peaks.
  • Rapid Workflow: Enzymatic release avoids lengthy immunoprecipitation steps.
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3D illustration of MapR mechanism showing RH-MNase fusion binding to an R-loop.

Overview: Fast, Antibody-Free R-Loop Detection

R-loops—three-stranded nucleic acid structures composed of a DNA-RNA hybrid and a displaced single strand of DNA—are critical regulators of gene expression and genomic stability. However, mapping them has traditionally been difficult. Standard methods like DRIP-seq require large amounts of DNA and rely on the S9.6 antibody, which can sometimes bind non-specifically to double-stranded RNA.

MapR (Micrococcal nuclease-aided proximity profiling of R-loops) is a breakthrough technique designed to solve these problems. Think of it as "CUT&Run for R-loops." Instead of using antibodies and harsh sonication, MapR uses a recombinant fusion protein: a catalytically inactive RNase H (which specifically recognizes RNA:DNA hybrids) linked to Micrococcal Nuclease (MNase).

When added to permeabilized cells, this protein binds to R-loops and, upon activation with calcium, cuts the DNA precisely around the hybrid. This releases the R-loop fragments into the solution for sequencing. The result is a fast, high-resolution map of R-loops that works with very low sample inputs, making it accessible for projects that were previously impossible with DRIP-seq.

Service Snapshot

  • Target: Native R-loops (RNA:DNA hybrids)
  • Probe: Recombinant RH-MNase Fusion
  • Key Benefit: Low Input & Speed
  • Application: Rare Cells & Clinical Tissue

Service Highlights

Superior Sensitivity for Low-Input Samples

Traditional R-loop mapping often requires micrograms of genomic DNA, forcing researchers to pool samples or grow millions of cells. MapR's "in situ" chemistry happens inside the nucleus of permeabilized cells. Because the signal (the R-loop DNA) is released into the supernatant while the rest of the genome stays behind, the background noise is extremely low. This allows us to generate high-quality data from limited material, such as FACS-sorted cells or small tissue biopsies.

Specificity Without Antibody Bias

The core of the MapR technology is the RNase H domain. Biologically, RNase H has evolved to recognize RNA:DNA hybrids with exquisite specificity. By using this protein domain instead of an antibody, MapR naturally avoids binding to double-stranded RNA (dsRNA) or G-quadruplexes that can confound S9.6-based assays.

High-Resolution Peak Mapping

In standard ChIP or DRIP, DNA is broken randomly by sonication, resulting in broad peaks (hundreds to thousands of base pairs wide). In MapR, the MNase enzyme acts like molecular scissors attached directly to the R-loop. It cuts the DNA right at the edge of the binding site. This produces sharp, narrow peaks that allow you to pinpoint exactly where R-loops start and stop, often revealing their precise localization at promoter-proximal pause sites.

Rapid Turnaround

Because the MapR workflow avoids the lengthy overnight immunoprecipitation and wash steps of ChIP/DRIP, the experimental timeline is significantly compressed. This efficiency allows us to deliver data faster, accelerating your research cycle.

Technical Comparison: MapR vs. DRIP-seq vs. R-ChIP

Feature MapR (Our Service) DRIP-seq R-ChIP
Methodology Enzymatic Cleavage (In Situ) Antibody IP (In Vitro) Protein Expression (In Vivo)
Input Requirement Low (<50k cells) High (Millions of cells) High (Transfection dependent)
Transfection Needed? No (Recombinant enzyme) No Yes (Plasmid expression)
Resolution High (MNase footprint) Low/Medium (Sonication) High (RNase H footprint)
Specificity High (RNase H based) Moderate (Antibody issues) High (RNase H based)
Turnaround Fast (Rapid workflow) Standard Slower (Cell culture time)
Best For Rare cells, Screening, Clinical Global abundance, Standard lines In vivo mechanism, Transfectable cells

Recommendation: Choose MapR if you have limited cell numbers or need higher resolution than standard DRIP. Choose R-ChIP if you want to study R-loops in living cells and can easily transfect them.

Our MapR Workflow: From Permeabilized Cells to Data

Our MapR service is streamlined to maximize data quality while minimizing sample loss.

1. Cell Permeabilization & Bead Binding

We bind your cells (or nuclei) to Concanavalin A (ConA) magnetic beads and treat them with a mild detergent (digitonin). This opens the cell membrane while keeping the nucleus intact.

2. RHΔ-MNase Binding

We add the recombinant RHΔ-MNase fusion protein. This protein diffuses into the nucleus and binds specifically to R-loops on the chromatin.

3. Targeted Cleavage

Calcium is added to activate the MNase enzyme. The enzyme cuts the DNA on either side of the R-loop, releasing the hybrid fragment into the solution.

4. Release & Sequencing

The supernatant containing the released R-loops is collected. We purify the DNA and construct sequencing libraries without the need for harsh sonication.

5. Sequencing & Analysis

Libraries are sequenced (PE150) and analyzed to identify enriched peaks.

Step-by-step workflow diagram of the MapR R-loop sequencing service.

Technical Specifications

We offer flexible formats to match your resolution and throughput needs.

Specification Details
Enzyme Recombinant RHΔ-MNase Fusion Protein
Library Prep Strand-Specific (dUTP method) to preserve directionality.
Sequencing Depth Standard: 20-30 Million PE150 reads per sample.
Resolution ~50-200 bp (MNase footprint).
Input Requirements Recommended: 100,000 cells. Minimum: 1,000 cells (with consultation).
Controls MNase-only control or IgG control (if applicable).

Recommended Applications of MapR

Understanding where and why R-loops form is critical for research into cancer biology, neurodegeneration, and basic gene control.

Profiling Rare Cell Populations

MapR's low input requirement makes it the only viable option for studying R-loops in FACS-sorted subpopulations, such as stem cells, circulating tumor cells, or specific neuronal subtypes.

Clinical Sample Analysis

For clinical biopsies where material is scarce and valuable, MapR allows for robust R-loop profiling without the need for large-scale tissue homogenization required by DRIP-seq.

Investigating G-Quadruplex Co-localization

R-loops often co-localize with G-quadruplexes (G4s) at active promoters. MapR's high resolution allows researchers to dissect the precise spatial relationship between these two regulatory structures.

Screening Drug Effects

The rapid workflow of MapR makes it suitable for medium-throughput screening of drugs (e.g., topoisomerase inhibitors) to assess their impact on R-loop formation and resolution kinetics.

Why Choose CD Genomics for MapR?

Optimized Protocol

We have refined the MapR protocol to ensure consistent enzymatic activity and minimal non-specific background.

Strict QC

Every project includes rigorous quality control steps, including fragment size analysis and enrichment validation at positive control loci.

Expert Bioinformatics

Our team is experienced in handling MNase-based data, ensuring accurate peak calling and footprinting analysis.

Custom Solutions

We can adapt the workflow for challenging sample types, such as frozen tissue or nuclei isolated from complex organs.

Sample Requirements

One of MapR's greatest strengths is its flexibility with sample input.

Sample Type Recommended Input Minimum Input Storage/Transport
Cell Lines 100,000 cells 1,000 cells* Cryopreserved (DMSO) or Flash Frozen pellet
Primary Cells (PBMCs, etc.) 100,000 cells 5,000 cells* Fresh or Cryopreserved
Fresh Tissue 10-20 mg ~5 mg Flash Frozen / RNAlater
Sorted Nuclei 50,000 nuclei 5,000 nuclei Flash Frozen pellet

*Note: For ultra-low input projects (<5,000 cells), please consult with our technical team to discuss library preparation strategies.

Key Deliverables

We deliver comprehensive data packages designed to answer your biological questions immediately.

Raw Data Files
FASTQ files (Clean reads).

Signal Tracks (BigWig)
Visualizing R-loop distribution across the genome. MapR data typically shows low background noise with sharp peaks at gene promoters and terminators.

Peak Calls (BED)
Precise coordinates of statistically significant R-loop sites.

QC Metrics & Analysis
Validation of the assay using known positive control loci (like the RPL13A gene) and optional differential analysis between conditions.

Case Study: Validating Native R-Loops at Active Promoters

G-quadruplexes (G4s) and R-loops often form in similar genomic regions, but understanding their interaction in living cells has been challenging due to the lack of specific tools. In a 2024 study, researchers sought to map these structures simultaneously to understand their regulatory roles.

To profile R-loops with high specificity, the team utilized an approach based on the RNase H1 Hybrid Binding Domain (HBD)—the same functional unit used in our MapR service. They integrated this with G4 profiling to see where these structures overlap genome-wide.

The RNase H-based mapping revealed that R-loops co-localize significantly with G4s, particularly at the promoters of highly active genes. The high resolution of the assay allowed the researchers to see that these structures are dynamically regulated by specific helicases (like Dhx9). The study confirmed that using the RNase H domain provides a specific and robust readout of native R-loops, distinct from the broader signals often seen with antibody-based methods.

Data showing R-loop enrichment at active promoters using RNase H-based mapping.

This study highlights the power of enzyme-based recognition (the core principle of MapR) for dissecting complex chromatin structures with high spatial resolution and specificity.

(Source: Genome-wide mapping of native co-localized G4s and R-loops in living cells, eLife, 2024. CC BY 4.0)

Demo Results (Representative Examples)

IGV tracks showing MapR signal enrichment at promoter regions.MapR Enrichment

Frequently Asked Questions

References

  1. Genome-wide mapping of native co-localized G4s and R-loops in living cells. eLife. 2024.
  2. MapR: A method for identifying native R-loops genome-wide. Cell Research. 2019.
  3. Mapping native R-loops genome-wide using a targeted nuclease approach. bioRxiv. 2018.
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