Development of a New (and Free) DNA Resource to Support the Forensic DNA Typing Community

NIST Standard Reference Materials (SRMs) have supported accuracy and traceability in forensic DNA typing methods since 1992. These SRMs are DNA extracts highly characterized for forensically relevant marker systems (e.g. STRs, SNPs, and mitochondrial genomes). As technology has advanced and sensitivity has increased, measurement challenges in forensic DNA typing have evolved. With these challenges, the community has requested SRMs for more complex materials to address commonly encountered measurement issues such as DNA mixtures, DNA degradation, and PCR inhibition. The stochastic nature of these sample types poses a challenge in meeting the robust characterization required for an SRM classification.

Given challenges with the development of SRMs for these sample types and in recognition of the need for biological samples, NIST has developed a new classification of exploratory material referred to as a “Research Grade Test Material (RGTM)”. RGTMs aim to evaluate fit-for- purpose needs within a community and to this end we are developing RGTM 10235 – Forensic DNA Typing Resource Material. The material is composed of a set of eight well-quantified DNA extracts. Components include three single source samples, two degraded samples, and three mixture samples. As part of the RGTM process, NIST is investigating automated methods for bottling, alternative sample tube types, and the addition of carrier RNA for stabilizing low- quantity samples.

In addition to the challenging nature of the samples requested, there is often a concern related to privacy issues and publicly sharing data generated from internally collected staff samples. Another motivation for developing the RGTM 10235 is to aid in the validation efforts by offering a set of DNA extracts with explicit informed consent. This will allow for the public sharing of STR profiles and facilitate open data sharing among laboratories and transparency with law enforcement stakeholders.

The RGTM program is collaborative, where the material is sent to laboratories with the understanding that data collected on the samples will be shared with NIST. RGTM 10235 will be distributed at no cost after the execution of a Material Transfer Agreement. At release, NIST will provide allele calls for the U.S. core loci and DNA concentration values for each component as assigned by digital PCR. In parallel, an RGTM 10235 data portal will be hosted at STRBase [https://strbase.nist.gov/Information/RGTM_10235]. Through this portal, laboratories can submit allele calls, quantification values, and mixture interpretation details (coming in 2024).

This information will be curated and anonymously posted on STRBase for comparisons and longitudinal evaluation of the long-term stability and performance of the material. This data will aid NIST in developing future reference materials more rapidly in support of the forensic DNA community.