In recent years, the potential to associate donor (from DNA results) with specific cell types (based on RNA analysis) using single nucleotide polymorphisms (SNPs) has been explored and recognized as a major advancement in forensic RNA typing.  

This method relies on SNPs in transcribed regions of body fluid-specific mRNA to link a cell type to a specific donor, whose presence is inferred from conventional forensic DNA typing. While the approach is promising, discrepancies frequently arise between the DNA and RNA-SNP data, primarily due to allelic dropout of RNA alleles. Understanding the mechanism underlying allele-specific expression is essential for advancing this method towards casework implementation.  

To address this, the role of quantitative trait loci (QTLs) as a potential cause of allele-specific expression (ASE) was investigated. Findings show how QTLs help explain the previously unresolved discrepancies and how QTL analysis can serve as a predictor of a gene’s susceptibility to ASE. Additionally, guidelines are provided for handling genes with increased risks of ASE, aiding the implementation of DNA and RNA-SNP-based donor-to-cell-type association in forensic casework. 

Authors

• Margreet van den Berge (Netherlands Forensic Institute, Netherlands) 
• Titia Sijen (Netherlands Forensic Institute, Netherlands)