Evaluating Somatic Mutational Contamination in Large-Scale Germline Genomic Studies

Area of Science:

• Genomics
• Human Genetics
• Bioinformatics

Background:

• Large-scale genomic studies rely on blood DNA to represent the germline genome.
• Somatic mutations, particularly from clonal hematopoiesis, can contaminate germline DNA samples.
• Existing variant allele frequency (VAF)-based filtering may not adequately remove these somatic artifacts.

Purpose of the Study:

• To systematically evaluate the limitations of current bioinformatics filtering methods in large-scale genomic studies.
• To investigate the characteristics and impact of somatic mutations misidentified as germline variants.
• To provide guidance for improving the accuracy of genetic association studies.

Main Methods:

• Analysis of germline genome data from large cohorts using mutational signatures.
• Systematic evaluation of rare variant filtering methodologies.
• Multivariable regression modeling to quantify somatic artifact burden.

Main Results:

• Rare variants identified as "germline" share mutational spectra with somatic mutations.
• These variants correlate with age, sex, and smoking status, known drivers of somatic mutation.
• An excess burden of somatic artifacts was estimated, exceeding mutation rates in some cancers.

Conclusions:

• Current filtering strategies are inadequate for distinguishing somatic contaminants from true germline variants.
• Somatic contamination introduces significant confounder effects, risking spurious associations and reverse causality.
• Refined filtering and inclusion of somatic mutagenesis factors are crucial for accurate genomic research.