3D Genome Assembly Using Hi-C Contact Maps
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Solution Overview
Problem
Current methods for genome assembly, particularly for genomes with substantial repetitive sequences like Aedes aegypti, struggle to produce high-quality, chromosome-spanning scaffolds due to difficulties in assembling repetitive regions and low coverage areas.
Innovation Solution
The method involves generating contigs and scaffolds from input sequencing reads obtained from a DNA proximity ligation assay, and then assembling larger sequences by overlapping, ordering, orienting, and merging these contigs and scaffolds to produce a final assembly, utilizing contact maps to guide the assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If clone libraries with physical coverage are used for genome assembly, then scaffolds can span large regions (1-15 megabases), but it is not feasible to achieve scaffolds that span entire chromosomes due to large repetitive regions
Solution Approach 1:
The patent transitions from one-dimensional linear assembly to three-dimensional spatial assembly by using Hi-C contact frequency data. This allows scaffolding across repetitive regions by leveraging spatial proximity information rather than relying solely on linear sequence overlap, enabling chromosome-spanning assemblies.
Solution Approach 2:
The patent introduces Hi-C contact frequency data as an intermediary to bridge repetitive regions that cannot be assembled using traditional methods. This intermediary provides long-range linking information that spans repetitive sequences, allowing contigs to be connected into chromosome-scale scaffolds.
2Quantity of substance
If short DNA sequence reads are used for genome assembly, then assembly can be performed with available sequencing technology, but repetitive sequences and low coverage regions create gaps that cannot be spanned
Solution Approach 1:
The patent merges short-read sequencing data with Hi-C contact frequency data to overcome the limitations of each individual data type. The short reads provide base-level accuracy while Hi-C data provides long-range connectivity, together enabling complete chromosome assemblies.
Solution Approach 2:
Hi-C contact frequency data serves as an intermediary that connects short-read assembled contigs across gaps in coverage. This intermediary information allows the assembly to span repetitive regions and low coverage areas that would otherwise create breaks in the assembly.
3Ease of manufacture
If traditional assembly methods are used, then assembly process is straightforward, but assembly quality deteriorates in genomes with substantial repetitive sequences
Solution Approach 1:
The patent introduces Hi-C contact frequency maps as an intermediary data layer that guides the assembly process through repetitive regions. This additional information source improves assembly precision without completely redesigning the assembly workflow, maintaining relative simplicity while dramatically improving quality.
Solution Approach 2:
The patent changes the parameters used for assembly by incorporating spatial distance metrics from Hi-C data alongside traditional sequence overlap parameters. This multi-parameter approach enables accurate assembly of repetitive regions while maintaining process feasibility.
Data Source
AI summary
Embodiments provide a method for sequencing and assembling long DNA genomes comprising generating a 3D contact map of chromatin loop structures in a target genome, the 3D contact map of chromatin loop structures defining spatial proximity relationships between genomic loci in the genome, and deriving a linear genomic nucleic acid sequence from the 3D map of chromatin loop structures.