DNA-Barcoded Nucleosome Spike-Ins for Chromatin Assay Normalization
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Solution Overview
Problem
Current chromatin mapping and accessibility assays lack reliable spike-in controls that are compatible with assays using tethered enzymes, such as MNase-seq, ATAC-seq, CUT&RUN, and CUT&Tag, and suffer from sample variability and antibody performance issues.
Innovation Solution
Development of DNA-barcoded recombinant nucleosomes with modified linker DNA and optional binding moieties for enzyme targeting, allowing use as spike-in controls in chromatin accessibility and mapping assays, including those using tethered enzymes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional chromatin mapping assays are used without engineered spike-in controls, then the assays can be performed with standard protocols, but they suffer from sample variability and lack reliable normalization
Solution Approach 1:
The invention creates simplified copy models of native chromatin using recombinant nucleosomes with standardized DNA sequences and histone proteins. These synthetic spike-in controls replicate the physical and chemical properties of endogenous chromatin, enabling reliable normalization without requiring complex native chromatin preparation procedures
Solution Approach 2:
The invention introduces engineered nucleosomes with modified parameters including standardized DNA sequences, defined histone variants, and controlled post-translational modifications. These parameterized spike-ins provide consistent reference points across samples, enabling quantitative normalization while maintaining assay simplicity
2Adaptability or versatility
If DNA-barcoded nucleosomes with linker DNA are engineered for enzyme targeting, then compatibility with tethered enzyme assays is achieved, but the manufacturing complexity increases
Solution Approach 1:
The nucleosome construct is divided into distinct functional segments: a core nucleosome particle, a linker DNA region for enzyme accessibility, and a DNA barcode for identification. This segmentation allows each component to be optimized and assembled independently through recombinant DNA technology, managing manufacturing complexity while achieving multi-assay compatibility
Solution Approach 2:
The engineered nucleosomes incorporate universal features including standardized linker DNA sequences that can be recognized by multiple enzyme types (MNase, Tn5, transposases) and modular barcode regions. This multi-functionality enables a single spike-in control design to serve multiple assay platforms, reducing the need for separate manufacturing processes for each application
3Measurement precision
If spike-in controls are introduced for normalization, then data accuracy improves, but the assay protocol complexity increases
Solution Approach 1:
The spike-in nucleosomes are pre-assembled with defined compositions, barcodes, and modifications before being introduced to the assay. This preliminary preparation of reference materials eliminates the need for complex in-protocol assembly steps, maintaining measurement precision while simplifying the actual assay execution
Solution Approach 2:
The DNA barcode serves as an intermediary element that enables precise quantification of spike-in recovery without interfering with the primary chromatin analysis. The barcode allows separate tracking and normalization calculations, improving measurement precision while adding minimal complexity through simple sequencing or detection steps
Data Source
AI summary
The present invention relates to DNA-barcoded recombinant nucleosomes and polynucleosomes that have been engineered for use as spike-in controls for chromatin accessibility assays, chromatin mapping assays, e.g., using tethered enzymes, as well as other chromatin assays. The invention further relates to methods of using the engineered DNA-barcoded recombinant nucleosomes in chromatin accessibility assays, chromatin mapping assays, as well as other chromatin assays.