Investigative Genetic Genealogy (IGG), also known as Forensic Investigative Genetic Genealogy (FIGG), has grown to be an invaluable tool for human forensic applications. IGG utilizes DNA sequencing methodologies to generate Single Nucleotide Polymorphism (SNP) profiles from unidentified human remains (UHRs) or evidentiary samples that have the potential to develop a vital investigative lead when searched against commercial genetic genealogical databases of known profiles. Laboratory processes of evidentiary DNA samples to generate the high-density SNP profiles suitable for database queries often face challenges due to DNA degradation induced by prolonged environmental exposure or an overabundant presence of complex metagenomic backgrounds overwhelming the human DNA of interest. A particularly beneficial laboratory method for overcoming these challenges is targeted enrichment prior to high throughput sequencing, where the human DNA fragments are captured by hybridization with biotinylated oligonucleotide probes containing the specific markers of interest.

To enable the targeted typing of a multitude of SNPs, we developed a workflow that incorporates Illumina-compatible library preparation and hybridization with a custom capture probe panel followed by high throughput sequencing. The custom probe panel was designed to target approximately 1.365 million SNPs spanning the human genome, including those commonly typed by direct-to-consumer (DTC) genetic testing companies and are thus present among the SNP data that comprise the genealogical databases used in forensic investigations (e.g., GEDmatch and FamilyTreeDNA), and Y-chromosome SNPs for paternal lineage identification. The resulting sequences from a DNA sample are analyzed with a custom bioinformatics workflow, generating a list of the genotypes for database queries. The compatibility of the panel design with multiple available library preparation and hybridization methods is beneficial for tailoring the processing methods to the varying quality of the DNA samples to be typed. This presentation will detail the laboratory processing steps and results obtained with hybridization capture and the custom probe panel for processing of pristine and low-quality DNA extracts.

This work was funded under Contract No. HSHQDC-15-C-00064, awarded by the DHS S&T to NBACC, a DHS federal laboratory operated by BNBI. Views and conclusions contained herein are those of the authors and should not be interpreted to represent policies, expressed or implied, of the DHS or S&T.

Authors

• Sana Enke (NBACC, United States of America)
• Karla Garcia (NBACC, United States of America)
• Rebecca Mitchell (NBACC, United States of America)
• Rebecca Just (NBACC, United States of America)