A T2T Benchmark Reveals How Reference Choice Shapes Human Genome Interpretation

The completion of telomere-to-telomere (T2T) human genomes has opened up a wider landscape of human genetic variation, yet existing benchmark resources are limited to regions considered highly accurate, based on current reference standards. Researchers have now created a near-perfect diploid T2T genome (T2T-LIN) from an individual of Chinese heritage and established a set of reference-based "truth sets" by comparing it to another near-perfect T2T reference genome from an ancestry-matched individual called T2T-YAO.

This benchmark test, which showed a typical ratio of heterozygous and homozygous single nucleotide variants (SNVs), allowed scientists to evaluate genome-wide effects of reference bias.

The study revealed that the choice of reference significantly impacts how genome information is interpreted. Linear T2T references derived from individuals with the same ancestry provided the most accurate representation of an individual's genetic variation, leading to more precise genome reconstructions than references that were not matched for ancestry or were based on graphs or combined data.

Benchmarking regions that were previously difficult to access due to their repetitive nature or structural complexity exposed limitations of current variant callers. These limitations were often hidden when using standard metrics for comparison.

To address these issues, the researchers developed T2T-LIN and YAO-LIN benchmarks that establish a framework for evaluating genome interpretation and variant discovery across almost the entire human genome, in line with the evolving era of T2T sequencing.