Systematic tuning retains more SNPs from fragmented keratinised-tissue DNA

A systematic evaluation of DNA analysis workflows found that tailored read-mapping parameters and a lower mapping-quality cutoff can improve computational efficiency while retaining more genuine single-nucleotide polymorphisms from highly fragmented DNA in keratinised tissues. The study, reported in the International Journal of Legal Medicine, focuses on a DNA profile that is substantially fragmented but generally has comparatively low levels of chemical damage, distinguishing it from both high-quality genomic DNA and ancient DNA.

Keratinised tissues offer a non-invasive and readily accessible source of DNA and are increasingly used in museum genomics, wildlife genetics and conservation studies. Their DNA also has growing importance in forensic work. However, existing read-mapping and variant-calling workflows had not been optimised for the distinctive combination of fragmentation and comparatively limited damage found in these materials. The researchers therefore evaluated key parameters used to map sequence reads and call variants, aiming to adapt the analytical process to the empirical properties of keratinised-tissue-derived genomic DNA, which the authors term kmDNA.

One part of the optimisation involved fine-tuning the -l and -o parameters of the BWA-ALN alignment tool. According to the study’s abstract, these changes substantially improved computational efficiency without reducing mapping accuracy or reliability. The source does not assign more specific biological functions to the two options or state that a particular parameter accounted for the efficiency gain. The result was instead a tested adjustment within the alignment workflow for DNA whose sequence reads are highly fragmented.

The investigators separately assessed the empirical distribution and quality characteristics of kmDNA to refine the criteria used to filter SNPs. They lowered the mapping-quality threshold for retaining a variant from greater than 40 to greater than 36. This modification maximised the retention of genuine genetic variants and significantly increased the number of usable SNPs, according to the reported evaluation. In practical terms within the tested workflow, the revised filter accepted a broader set of variant calls while preserving the mapping quality required by the optimised analytical framework.

Across diverse sample types and data-quality conditions, the resulting optimisation framework showed strong stability and reproducibility. The study is methodological rather than clinical: it evaluates read mapping, SNP filtering and computational performance, not a patient outcome or the accuracy of downstream population-genetic conclusions. Its demonstrated scope is the analysis of highly fragmented DNA from keratinised tissues. The findings provide a basis for applying kmDNA in population-genetic analyses and large-scale genomic studies, while the authors also highlight the need to optimise analytical parameters specifically for other highly fragmented DNA datasets. The supplied evidence supports this data-specific approach without identifying a single universal configuration for all fragmented samples or reporting results beyond the datasets evaluated in the study.

Subject of Research: Read-mapping and SNP-filtering optimisation for highly fragmented DNA from keratinised tissues

Article Title: Optimised strategies for read mapping and snp filtering of highly fragmented DNA from keratinised tissues

Article References: Zhou, Y., Su, C., Cui, L., Liu, B., Gao, P., Yang, S., & Xu, Y. (2026). Optimised strategies for read mapping and snp filtering of highly fragmented DNA from keratinised tissues. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04045-z

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04045-z

Keywords: keratinised-tissue DNA, fragmented DNA, read mapping, SNP filtering, BWA-ALN, variant calling, kmDNA, museum genomics, wildlife genetics, population genetics, Optimised, strategies