GWAS shows the genetics behind cell-free DNA and highlights the importance of p.Arg206Cys in DNASE1L3 for non-invasive testing.

The properties of cell-free DNA (cfDNA) are intensely studied for their potential as non-invasive biomarkers. We explored the effect of common genetic variants on the concentration and fragmentation properties of cfDNA using a genome-wide association study (GWAS) based on low-coverage whole-genome sequencing data of 140,000 Dutch non-invasive prenatal tests (NIPTs). Our GWAS detects many genome-wide significant loci, functional enrichments for phagocytes, liver, adipose tissue, and macrophages, and genetic correlations with autoimmune and cardiovascular disease. A common (7%) missense variant in DNASE1L3 (p.Arg206Cys) strongly affects all cfDNA properties. It increases the size of fragments, lowers cfDNA concentrations, affects the distribution of cleave-site motifs, and increases the fraction of circulating fetal DNA during pregnancy. For the application of NIPT, and potentially other cfDNA-based tests, this variant has direct clinical consequences, as it increases the odds of inconclusive results and impairs the sensitivity of NIPT by causing predictors to overestimate the fetal fraction.