Analysis of genomic variation in non-coding elements using population-scale sequencing data from the 1000 Genomes...

Area of Science:

• Genomics and Evolutionary Biology
• Human Genome Evolution
• Population Genetics

Background:

• Non-coding genomic regions, such as transcription-factor binding sites (TF-binding sites) and non-coding RNAs (ncRNAs), are estimated to be under more natural selection than protein-coding sequences.
• However, these non-coding elements have received less research attention compared to coding sequences.
• Understanding selective pressures on non-coding elements is crucial for a comprehensive view of genome evolution.

Purpose of the Study:

• To investigate and quantify selective pressure on non-coding genomic elements using next-generation sequencing data.
• To compare selective constraints across different types of genomic variations (SNPs, indels, SVs) within non-coding elements.
• To analyze how genomic properties and element subclasses influence selective pressure.

Main Methods:

• Utilized next-generation sequencing data from the 1000 Genomes Project pilot phase.
• Developed a framework to integrate variation data with non-coding elements, calculating population-based metrics.
• Employed element-aware aggregation procedures and bootstrapping techniques to analyze selective pressure across element structures.

Main Results:

• TF-binding sites and ncRNAs show less selective constraint for single-nucleotide polymorphisms (SNPs) than coding sequences (CDSs), but more than neutral regions.
• Counter-intuitively, TF-binding sites and ncRNAs exhibit stronger selective constraint for insertions/deletions (indels) than for SNPs, relative to CDSs.
• Selective pressure varies within element subclasses, correlating with genomic properties like expression levels and motif conservation; micro-RNA seed regions and their targets are under stronger selection.

Conclusions:

• Non-coding elements, particularly TF-binding sites and ncRNAs, are under significant natural selection, with distinct patterns for different variation types.
• Genomic properties and element substructures, such as expression levels and conserved motifs, modulate the extent and type of selective pressure.
• Structural variations (SVs) interact with genomic elements in unique ways, influencing their evolutionary trajectory.