


Application of Laser Microdissection (LMD) to Expedite Forensic Sexual Assault Casework Kelli Raley, MSFS North Louisiana Criminalistics Laboratory Shreveport, LA NFSTC Laser Microdissection Workshop, 2007
LMD Microscopy Research and Experience: Highlights • Why LMD for North Louisiana Crime Lab (NLCL) Casework? • Elimination of Manual Extraction • Reproducibility/Sensitivity • Troubleshooting • Single Amplification/Optimization • Absence of Sperm • LMD: Streamlined, Novel Process
Why Laser Microdissection? ~45% of all NLCL DNA cases involve sexual offense so Need to eliminate bottleneck in DNA analysis
Disadvantages of LMD • Initial cost • Novel validation • ~$4.25 each for PEN slides • PEN foil contains pores ≈ sperm • Except for PEN slides, no other consumables for Leica
Advantages of LMD • Eliminate traditional extraction • Absolute separation of sperm and epithelial DNA • Effect of traditional PCR challenges minimized • Decrease analysis time for a sexual assault sample
Elimination of Traditional Extraction • Direct amplification after LMD?
Elimination of Traditional Extraction • Direct amplification after LMD? • Pre-amplification Lysis • Constraints • Can’t adversely affect PCR • Limited volume (10µL) • Lyse-N-Go™ PCR Reagent (LNG) • 25µL reaction vs. 50µL • Recombinant Proteinase K
Comparison of Pre-Amplification Treatments • 150 sperm • 25µL volume • Profiler Plus • 30 PCR cycles
Pre-amplification Lysis: ProK/DTT • Cut directly into water • Recombinant ProK • Lysis incubation in TC • PCR reaction components to same tube • Amplify, analyze
Additional Experiments: Sensitivity • PCR cycles • amplification reaction volume with reduced volume PCR (RVPCR) • 15µL, 10µL • PCR with fewer sperm for lowest detection limit
25µL 15µL 10µL ProK/DTT150 sperm, 30 cycles Avg PH ~880 RFUs Avg PH ~948 RFUs Avg PH ~2540 RFUs
Reproducibility • Profiler Plus • 30 PCR cycles
drop-out ProK/DTT100 sperm, 30 cycles 25µL Avg PH ~157 RFUs 10µL Avg PH ~2631 RFUs
drop-out ProK/DTT50 sperm, 30 cycles 25µL Avg PH ~174 RFUs 10µL Avg PH ~556 RFUs
LMD together with Pre-amplification Lysis: • Elimination of traditional extraction possible • Absolute separation of sperm and epithelial DNA possible
Exciting! 50 sperm, 30 cycles, 10µL Profiler Plus
drop-out 50 epi nuclei, 30 cycles, 10µL Profiler Plus
drop-out 25 epi nuclei, 30 cycles, 10µL Profiler Plus
Early NLCL Research for LMD: Summary • Replace DNA extraction and purification with novel pre-amplification lysis • Physical and complete separation of sperm and epithelial DNA • RVPCR, 30 cycles, reproducible • Sensitivity: 50-150 sperm • http://www.promega.com/geneticidproc/ussymp16proc/abstracts/langley.pdf
From Research to Validation . . . • Troubleshooting • Identifiler for single amplification • How many sperm? • No sperm observed
Troubleshooting • Static • humidity • cuttings into 25µL vs 50µL • Electropherogram Conundrum • “dye-saturated” e-grams, • Contamination? • Non-specific binding? • Profiler Plus vs. Profiler vs. Identifiler
From Research to Validation . . . • Troubleshooting • Identifiler for single amplification • How many sperm? • No sperm observed
Identifiler Optimization • TE-4 vs DepC H2O • Vary Tris, pH 8.0 in TE-4: normal, 1/2x, 1/4x, 1/5x • PCR cycling • 28+6, 20+14, 20+10 cycles • 31 cycles • MgCl2 • Vary extra Mg2+ added • 0.5mM – 1.5mM still optimal for RVPCR
50 sperm, Identifiler, 30 cycles drop out 24/29
Identifiler Optimization 29/29 alleles
From Research to Validation . . . • Troubleshooting • Identifiler for single amplification • How many sperm? • No sperm observed
50 sperm, Identifiler 29/29 alleles
25 sperm, Identifiler 23/29
25 sperm, Identifiler 27/29
15 sperm, Identifiler 20/29
15 sperm, Identifiler 25/29
From Research to Validation . . . • Troubleshooting • Identifiler for single amplification • How many sperm? • No sperm observed
No sperm observed • Cut spot from PEN slide • Organic extraction • Qiagen EZ1? • YSTR and STR panels
Advantages of LMD • Eliminate traditional extraction • Absolute separation of sperm and epithelial DNA • Effect of traditional PCR challenges minimized • Decrease analysis time for a sexual assault sample through novel process
Advantages of LMD Effect of traditional PCR challenges minimized • Simplify mixtures, simplifying interpretation • Difficult statistical interpretations eliminated • Less tendency for contaminants/inhibitors? • Increase PCR cycles to enhance LCN sperm analysis
Novel Process The NLCL DNA section envisions a new way of processing and storing sexual assault samples
Sexual Assault Sample Processing Time - LMD • Presumptive testing (AP, PSA), slide preparation • Examine for sperm, cut nuclear material • Drying of TE-4 • Pre-amp (in TC) • PCR and gel 2 hours (1hr shake) 15 min -1 hour 45 min overnight (3.5 hrs) 1 day
LMD Coupled With Pre-amplification Lysis . . . . . Improves and streamlines the analysis of sexual assault evidence AND Frees up analyst time!
Current Considerations • Shorten lysis time of LMD harvested cells • Mixture Studies • Epithelial nuclei, still necessary? • Non-probative samples • Considerations for casework implementation