Defining key criteria for microhaplotype locus selection in forensic genetics: Progress and recommendations by the...

Area of Science:

• Forensic genetics
• Population genetics
• Molecular biology

Background:

• Growing interest in microhaplotypes (MHs) for forensic genetics necessitates standardization.
• The Microhaplotype Working Group (MWG) formed to address standardization needs in MH marker development.
• Previous forensic community discussions highlighted the need for defined criteria for MH loci selection.

Purpose of the Study:

• To summarize the MWG's progress in defining criteria for identifying and characterizing microhaplotype (MH) loci for forensic use.
• To establish locus nomenclature and allele definitions for MHs.
• To outline challenges and provide recommendations for MH marker selection and implementation in forensic casework.

Main Methods:

• Consensus building on critical marker characteristics for MH selection.
• Utilizing the MicroHapDB database for locus nomenclature and tracking.
• Defining exclusion criteria for MH loci, including genomic location, length, linkage, and sequence complexity.

Main Results:

• Consensus reached on key MH selection parameters, prioritizing the effective number of alleles (Ae).
• Identified 1148 theoretically suitable MH loci based on defined criteria.
• Established exclusion criteria for MHs located in repetitive elements (LINEs, SINEs, LTRs), exceeding 250 bp, or containing indels/low complexity near SNPs.

Conclusions:

• The MWG has developed a foundational framework for selecting and implementing microhaplotype loci in forensic genetics.
• Standardized criteria and nomenclature will facilitate the development of robust MH panels for applications like mixture deconvolution and ancestry estimation.
• The identified MH loci and established criteria pave the way for future recommendations for forensic casework implementation.