Single-Molecule Chromatin Mapping via MINSTED Imaging
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Solution Overview
Problem
Current methods for mapping chromatin modifications, such as ChIP-seq, are limited in their ability to detect combinatorial marks on individual nucleosomes, distinguish between different alleles or cells, and provide absolute quantification of modification levels, hindering the understanding of gene regulation and progression towards understanding human genome regulation.
Innovation Solution
A robust single-molecule imaging system is developed to analyze chromatin modifications by covalently linking oligonucleotide sequences to chromatin fragments, purifying them, and binding them to a solid support for imaging, allowing for multiplexed analysis and visualization of combinatorial protein-nucleic acid interactions and histone modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ChIP-seq is used to map chromatin modifications, then genome-wide chromatin state maps can be obtained, but the ability to detect combinatorial marks on individual nucleosomes is limited
Solution Approach 1:
The invention segments the chromatin analysis process into two distinct phases: (1) genome-wide mapping using ChIP-seq to identify chromatin states across the entire genome, and (2) single-molecule imaging using MINSTED to resolve combinatorial marks on individual nucleosomes. This segmentation allows each method to operate at its optimal scale, with ChIP-seq providing broad coverage and MINSTED providing high-resolution molecular detail, thereby resolving the contradiction between genome-wide mapping capability and single-nucleosome detection precision.
Solution Approach 2:
The invention introduces an intermediary approach where chromatin fragments are first enriched through ChIP using modification-specific antibodies, then subjected to ultra-sensitive single-molecule imaging. This intermediary ChIP step serves as a bridge that concentrates rare modified nucleosomes from complex chromatin mixtures, enabling the subsequent MINSTED imaging to detect combinatorial marks with high precision while maintaining genome-wide context through the initial ChIP enrichment.
2Measurement precision
If ChIP is used to identify genomic location of modifications, then chromatin state maps can be generated, but absolute quantification of modification levels cannot be provided
Solution Approach 1:
The invention replaces the indirect, relative quantification approach of traditional ChIP (which relies on antibody enrichment and sequencing read depth) with a direct, absolute quantification method using single-molecule imaging. By counting individual fluorescently-labeled nucleosomes and their modification markers through MINSTED, the system provides absolute quantification of modification levels without relying on complex controls or normalization procedures, thereby achieving precise measurement while maintaining operational simplicity.
3Measurement precision
If ChIP-seq is used to map chromatin modifications, then genome-wide coverage is achieved, but the ability to distinguish combinatorial modifications on the same nucleosome is lost
Solution Approach 1:
The invention merges the strengths of two complementary approaches: ChIP-seq provides genome-wide coverage to identify regions of interest, while MINSTED single-molecule imaging provides high-resolution detection of combinatorial modifications on individual nucleosomes. By combining these methods in an integrated workflow where ChIP-enriched chromatin is subjected to MINSTED imaging, the system achieves both genome-wide context and single-nucleosome resolution, allowing simultaneous detection of multiple modification marks on the same nucleosome while maintaining broad genomic coverage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the precise mapping of combinatorial histone modifications, transcription factor occupancy, and genomic location of single nucleosomes, overcoming the limitations of existing methods and providing insights into gene regulation, cancer initiation, and drug target screening.
Implementation Method 1
the oligonucleotide sequence is configured to bind to a capture molecule
Implementation Method 2
incubating the solid support with a first set of at least one labeling ligand with specific binding affinity for a target molecule
Data Source
AI summary
The present invention provides for single-molecule profiling of combinatorial protein modifications and single-molecule profiling of combinatorial protein modifications combined with single-molecule sequencing of protein/nucleic acids complexes. High-throughput single-molecule imaging was applied to decode combinatorial modifications on millions of individual nucleosomes from pluripotent stem cells and lineage-committed cells. Applicants identified bivalent nucleosomes with concomitant repressive and activating marks, as well as other combinatorial modification states whose prevalence varies with developmental potency. Applying genetic and chemical perturbations of chromatin enzymes show a preferential affect on nucleosomes harboring specific modification states. The present invention also combines this proteomic platform with single-molecule DNA sequencing technology to simultaneously determine the modification states and genomic positions of individual nucleosomes. This novel single-molecule technology can be used to address fundamental questions in chromatin biology and epigenetic regulation leading to novel therapeutics and diagnostics.