Extensive Hidden Genomic Mosaicism Revealed in Normal Tissue

Area of Science:

• Genomics
• Human Genetics
• Computational Biology

Background:

• Genomic mosaicism, resulting from post-zygotic mutations, is increasingly recognized in normal human tissues.
• Detecting low-frequency mosaic mutations is challenging due to cellular heterogeneity.
• Previous studies have cataloged mosaic mutations, but comprehensive analysis remains difficult.

Purpose of the Study:

• To develop and apply a computational method for characterizing mosaic megabase-scale structural mutations.
• To identify novel mosaic mutations and validate previously known ones in a large cohort.
• To investigate the distribution and frequency of mosaic mutations across the genome.

Main Methods:

• Applied a computational method utilizing estimated haplotypes to analyze data from 31,100 Genome-Wide Association Study (GWA) subjects.
• Performed in silico validation of 293 known somatic mutations.
• Identified 794 novel mosaic structural mutations, many at lower aberrant cell fractions.

Main Results:

• Successfully validated existing somatic mutations and discovered a significant number of novel mosaic mutations.
• Observed that mosaic mutations occur nonrandomly across the genome, with specific chromosomes and loci showing higher mutation rates.
• Found a nearly threefold higher rate of clonal mosaicism compared to previous surveys.
• Results support the association between clonal mosaicism and advanced age.

Conclusions:

• The developed haplotype-based computational method enhances the discovery of mosaic structural mutations.
• Mosaic structural mutations are more prevalent than previously estimated, particularly at lower cell fractions.
• Future population surveys for mosaic structural mutations should incorporate haplotypes for improved detection.